Tag: gardening

Categories
native plants Pollinator gardening

A Constellation of Blue

A constellation of pale blue flowers tops each Heart-Leaved Aster (AKA Blue Wood Aster or Symphyotrichum cordifolium).  Like all asters, it offers precious pollen and nectar to pollinators and beneficial insects at summer’s end.  The plant itself is a larval host for butterflies and moths.1

In nature, Heart-Leaved Aster grows in moist to dry deciduous woodlands, woodland borders, next to woodland paths, rocky wooded slopes, upland meadows, thinly wooded bluffs, shaded stream banks, and upland forests.1,5

Highly adaptable, Symphyotrichum cordifolium accepts clay, loam and sandy soils.  It grows from one to three feet tall and spreads from eighteen inches to two feet.  This aster thrives in zones three to eight.  It grows in light shade to part sun and moist to dry conditions.1

The leaves of Symphyotrichum cordifolium are highlighted by its scientific name.  Unlike the thin, lance-shaped leaves of most asters, this plant has broader, heart shaped ones.  Cordifolium  means heart-shaped and (cordi-)  means leaves (folium).  And so, the Heart-Leaved Aster!  

The leaves can reach five inches long and three inches across.  They become smaller moving up the plant. The lower leaves are fully heart-shaped (or cordate).  But the upper leaves become more oval and may be fully ovate.  They are medium green and smooth.1

The flowerheads are the highlight of the Heart-Leaved Aster!  Ranging from six inches to eighteen inches long, these conical heads shine with lavender, light-blue violet or white florets.  Each of these half inch florets has seven to fifteen petals (ray florets) and a yellow center of disc florets.1  

Once the disc florets are fertilized, the center turns a mauve pink adding visual interest to the flowerhead.  Floral bracts cover the base of each floret.  The bracts are pale with dark green tips.1

One of the first natives in my garden, I’ve grown this plant for close to 20 years.  I’ve always found is covered with flowers, pollinators and beneficials of all kinds.  That said, it has a few challenges.

It spreads by runners and by self-seeding.  When Heart-Leaved Aster’s happy, it can really colonize a garden.  It is easy to pull, and you can clip the seed heads to prevent self-seeding.1

Poorly drained soil can lead to powdery mildew, leaf spots and rust.  If the weather is too hot and dry, this aster often loses its lower leaves.  I plant it in the middle of the bed.  This location hides leaf loss and helps cover any trouble on the other leaves.4

Finally, like other asters, herbivores love it.  Rabbits, deer, ground hogs, etc., eat it, especially in the Spring.  Use whatever repellents preferred.  I also plant asters among plants animal don’t like, such as, iris.

The free herbivore pruning helps later in season though.  In fact, Symphyotrichum cordifolium benefits from pruning back several times before mid-summer.  This attention helps increases bushiness, controls height and might even eliminate the need to stake it!4

Heart-Leaved Aster draws crowds of pollinators and beneficial insects.  Like all Symphyotrichum, it is a keystone plant.  There are two types of keystone species:  one type acts as hosts for butterfly and moth caterpillars and the other feeds specialist bees.  The bee associated keystone plants also serves generalist bees.  Asters are both.2

Long-tongued bees, short-tongued bees, butterflies, moths, skippers, wasps and beetles all seek out its nectar and pollen.  The Xerces Society for Invertebrate Conservation designate Symphyotrichum cordifoliumof Special Value to Native Bees and state it Supports Conservation Biological Control.  Bumblebees find it especially helpful.1,6 

S. cordifolium blooms when new bumblebee queens emerge, males hatch and mating flights occur.  I find males sleeping on the plants on cool late summer and early autumn mornings.  The flowers provide important energy resources for successful mating flights and overwintering queens.

Heart-Leaved Aster support many specialist bees.  As a keystone plant for pollen specialist bees, the Symphyotrichum genus feeds several mining bees in the Andrena genus.   Specifically, these include Andrena (Callandrena s.l.) asteris, Andrena (Callandrena s.l.) asteroides, Andrena (Cnemidandrena)hirticincta, Andrena (Cnemidandrena) nubecula, Andrena (Callandrena s.l.) placata, Andrena (Callandrena s.l.) simplex, and Colletes simulans.5

Heart-Leaved Aster is also visited by metallic green sweat bees, Halictus (sweat bees), Ceratina (small carpenter bees) and honeybees (Apis).

Numerous adult butterflies and skippers nectar at the Heart-Leaved Asters including migrating Monarchs (Danaus plexippus) and Red Admirals (Vanessa atalanta).  In its role as a keystone plant, it feeds many caterpillars from butterflies and, especially, moths.  Different larvae eat every part of the plant.1

By supporting moths, Symphyotrichum cordifolium contributes to pollination of wild plants overall.  Some flowers evolved a plant pollinator relationship with moths.  These flowers usually open at night, are white or pale, and have a stronger fragrance at night.  Moths use scent to find food and mates.  Yucca is a well-known example.7  

However, moths provide much more extensive pollination services.  Like generalist bees, some moths also visit different types of flowers.  Most of these plants aren’t larval hosts.  Some are also pollinated by bees.  When they’re bee pollinated, moths supplement the bee’s work.7

In addition, moths are more efficient than bees in some cases.  In the past, studies only measured pollen on mouthparts.  But moths carry a lot of pollen on their hairy underbelly.  When they land on a flower, their belly presses against the stigma to transfer pollen.7,8

Moths usually fly over longer distances than bees.  Bees tend to stay near their nest when possible.  Moths add genetic diversity by bringing pollen from distant plant populations.7

A variety of moth and butterfly caterpillars use Symphyotrichum cordifolium.  Different larvae eat flowers, seeds, and leaves while others bore through stems and/or roots.  I’ve detailed some different species and which plant parts they eat in the next few paragraphs.3

Chlosyne nycteis (Silvery Checkerspot butterflies) and Phyciodes tharos (Pearl Crescent butterflies) consume foliage.  Some moths also devour the leaves, such as, Pale-Banded Dart (Agnorisma badinodis(syn. Xestia badinodis)), Sharp-Stigma Looper Moth (Ctenoplusia oxygramma (syn. Agrapha oxygramma)), Halloween Paint (Cucullia alfarata), Rusted Paint (Cucullia postera), Confused Eusarca (Eupithecia confusaria), Lost Sallow (Euplexia devia), Green Leuconycta (Leuconycta diphteroides), Small Brown Quaker (Pseudorthodes vecors) and Dimorphic Gray (Tornos scolopacinarius).3

Leaf miners include Gracillarlid Moth sp. (Acrocercops astericola), Tischeriid Moth sp. (Astrotischeria astericolaI), Scythridid Moth sp. (Landryia impositellaI) and Bucculatricid Moth sp. (Bucculatrix staintonella).3

Some feed on developing seeds and/or flowers including Blackberry Looper (Chlorochlamys chloroleucaria), White-Dotted Groundling (Condica videns (syn. Platysenta videns)), Common Pug (Eupithecia miserulata), Spotted Straw (HeIliothis turbatus), Tortricid Moth sp. (Phaneta parmatana), Tortricid Moth sp. (Phaneta tomonana), Common Tan Wave (Pleuroprucha insulsaria), Arcigera Flower Moth (Schinia arcigera), Goldenrod Flower Moth (Schinia nundina), Northern Flower Moth (Schinia septentrionalis), Wavy-Lined Emerald (Synchlora aerate) and Striped Garden Caterpillar (Trichordestra legitima).  Some moths consume foliage in addition to developing seeds and/or flowers.  These include Black Arches (Melanchra assimilis) and Dark-Spotted Palthis (Palthis angulalis).3

And finally, moth larva that bore through stems and/or roots are  Aster Borer Moth (Carmenta corn) , Tortricid Moth sp. (Eucosma robinsonana), Burdock Borer Moth (Papaipema cataphracta), Aster Borer Moth (Papaipema impecuniosa), Tortricid Moth sp. (Phaneta essexana) and Tortricid Moth sp. (Sonia canadana).3 

I hope you enjoyed this look at the Heart-Leaved Aster as much as I have.  I’d love to hear about your plant adventures in the garden or the wild!  Please feel free to contact me with a story, comment or question!

Happy Gardening,

Mary

Bibliography:

  1. “Blue Wood Aster (Symphyotrichum Cordifolium).” Accessed December 1, 2024. https://www.illinoiswildflowers.info/woodland/plants/bl_woodaster.htm. Accessed December 1, 2024.
  2. “Keystone Native Plants:  Eastern Temperate Forests-Ecoregion 8.” https://www.nwf.org/-/media/Documents/PDFs/Garden-for-Wildlife/Keystone-Plants/NWF-GFW-keystone-plant-list-ecoregion-8-eastern-temperate-forests.ashx?la=en&hash=1E180E2E5F2B06EB9ADF28882353B3BC7B3B247D
  3. “Moth Table (Symphyotrichum Spp.).” Accessed December 1, 2024. https://www.illinoiswildflowers.info/woodland/tables/table29.html.
  4. “Symphyotrichum Cordifolium – Plant Finder.” Accessed December 1, 2024. https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=a788.
  5. “Symphyotrichum Cordifolium (Blue Wood Aster, Common Blue Wood Aster, Heart-Leaved Aster) | North Carolina Extension Gardener Plant Toolbox.” Accessed December 1, 2024. https://plants.ces.ncsu.edu/plants/symphyotrichum-cordifolium/.
  6. “Symphyotrichum Cordifolium (Broad-Leaved Aster) | Native Plants of North America.” Accessed December 1, 2024. https://www.wildflower.org/plants/result.php?id_plant=syco4.
  7. Xerces Society. “The Night Shift: Moths as Nocturnal Pollinators.” Accessed December 1, 2024. https://xerces.org/blog/the-night-shift-moths-as-nocturnal-pollinators.
  8. “Moths are more efficient pollinators than bees, shows new research.”  Accessed December 1, 2024. Ellis, Lauren, https://www.sussex.ac.uk/broadcast/read/60568.
Categories
native plants Pollinator gardening

A Fabulous, Fuzzy Flower

Big, bold and filled with butterflies, Sweet Joe-Pye Weed (Eutrochium purpureum) stands out in any garden.  Large mauve-purple flowers feed masses of pollinators.  Not only do butterflies, moths and skippers nectar at the blooms but various caterpillars feed on it.10

Eutrochium purpureum grow in zones four to nine.  It usually ranges from three to seven feet tall.  In a drier location, it can flower at only one foot high and, in an ideal spot, can reach eight to ten feet.2,3,10  

It prefers partial shade to full sun and moist to medium, even moisture conditions.  Rich, loamy soil is ideal.  Eutrochium purpureum spreads by seeds and runners.  

In nature, it’s found in open woodlands, partially shaded seeps, savannas, partially shaded riverbanks and streambanks, thickets, in open woodlands, wet meadows, wooded slopes and low moist ground.2,3,8,10

Given these natural habitats, Sweet Joe-Pye weed easily adapts to wildflower gardens, naturalized landscapes and perennial borders.  Its moisture tolerance means  Eutrochium purpureum enjoys the edges of rain or water gardens.  Recently, Sweet Joe-Pye Weed began self-seeding near my rain gardens.  Finally, it suits both formal and informal settings.

Sweet Joe-Pye Weed will react to less-than-ideal conditions.  In full shade, it becomes leggy and may  fall over.  If it dries out, its leaves turn yellowish green.  

In my garden, it grows tallest in a rainy year.  In partial shade, the plants thrive even without extra water.  In full sun, the plants are more likely to need staking possibly from too little water. 1,2,3,10    

If a shorter plant is preferred, Sweet Joe-Pye Weed can be cut back to approximately two feet in late spring or early summer.  These plants usually bloom around the same time as those that haven’t been cut.  The flowers are a generally a little smaller than usual.1

Don’t give up on this one in the Spring!  It tends to sleep late and the stems develop randomly.  But it has been a very reliable grower in my garden—returning with full and abundant growth each year.

Chicago Botanic Garden grew a variety of Eutrochium spp. and related plants in an evaluative study between 2001 and 2013.  They trialed each genus between four and six years.  Eutrochium purpureum performed well each year with flowers up to twelve inches across.  It suffered from powdery mildew one year but not in others.1

Sweet Joe-Pye Weed has a straight, unbranched, light green stem giving the plant an outstanding erect habit.  The leaf nodes are enlarged and naturally purple.  Some plants have more purple on the stem than others. 2,3,10    

Shallow, fibrous roots support the plant.  Sweet Joe-Pye weed spreads as a clump as well as self-seeding.  If it grows in an unwanted place, the plants are easy to pull.

Eutrochium purpureum’s leaves form an attractive whorl around its stem.  Growing in groups of three to five, the medium green, the matte leaves are ovate to lanceolate with lightly serrated edges.  The lower surface is pale green and may be slightly hairy.  Some ecotypes have vanilla-scented foliage.10

In mid-summer to early fall, Sweet Joe-Pye Weed’s magnificent flowers grace the garden.  The main bloom sits  at the top of the stem.  On established plants, side blossoms form below this head adding to the show. 

Each compound head can measure up to 12 to 18 inches across and are made up of one or more panicles.  In my Southern Michigan garden,  Eutrochium purpureum’s flowerheads range from five inches to twelve inches across.  They are most often between five and eight inches.

Blooms range from whitish pink to purplish pink.  I find the more sun, the deeper the flower color.  Plants growing in deep shade have almost white flowers.  Flowers carry a vanilla scent.

These superb blooms have five to eight disk florets per panicle and no ray florets.  The overall flowerhead is slightly dome shaped. Each floret has a series of overlapping pink, oblong bracts.  As they open, a divided white style is strongly exerted (extended past the floret) giving the bloom a fuzzy look. 2,3,8,10  

Numerous pollinators forage on the compound flowerheads of Sweet Joe-Pye Weed.  Most seek out nectar.  Eutrochium purpureum secretes its nectar at the base of the style.  Each tiny, blooming floret offers a supply.2,3,8,10  

The Xerces Society for Invertebrate Conservation declared Eutrochium purpureum of Special Value to Native Bees.2  Visiting bees include Bombus spp. (bumblebees), Melissodes spp. (miner bees), Coelioxys (cuckoo bees), Agapostemon (metallic green sweat bees) and Megachile spp. (leaf-cutting bees).    In my garden, I’ve also seen other sweat bees like Halictus spp., honey bees (Apis app.) and large and small carpenter bees, Xylocopa spp. and Ceratina spp.

Most of these bees collect nectar.  But Bombus spp. (bumblebees) and Melissodes spp. (miner bees) also gather pollen.8,10

Butterflies, moth, and skippers seek out Sweet Joe-Pye Weed in the mid-summer to early fall.  Celastrina(Azure Butterflies), Epargyreus clarus (Silver Spotted Skipper), Limenitis arthemis arthemis (White Admiral Butterflies), Nymphalis urticae (Milbert’s Tortoiseshell Butterflies), Papilio glaucus (Eastern Tiger Swallowtail Butterflies), and Danaus plexippus (Monarch Butterflies) sip the nectar from the fluffy, pink flowerheads.

Eutrochium purpureum is also a larval host supporting several moth caterpillars.  These eat its leaves and other parts.  Emmelina monodactyla (Common Plume Moth), Perigea xanthioides (Red Groundling), Phragmatobia fuliginosa (Ruby Tiger Moth), and Eupithecia miserulata (Common Pug) all feed on Sweet Joe-Pye Weed’s leaves. Carmenta bassiformis (Eupatorium Borer Moth) consumes the roots.  Schinia trifasciata (Three-Lined Flower Moth) relies on its flowers. 4,5,6,8,9,10

Beneficial insects are not particularly attracted to Eutrochium purpureum.  Flies, thread-waisted and sand wasps occasionally visit. Instead, these short-tongued beneficials flock to another Eutrochium—the white blooming Boneset (Eupatorium perfoliatum).8 But that’s the subject for another blog!

I hope you’ve enjoyed hearing about Sweet Joe-Pye weed—a stunning, versatile and useful plant.  Eutrochium purpureum is easily available at most native plant nurseries.  Next year those big, fuzzy flowers could be blooming in your garden!

If you’ve enjoyed this blog and would like to leave a comment or share a story, please contact me in the box below!

Warm Regards,

Mary

References:

  1. Hawke, Richard. “A Comparative Study of Joe-Pye Weeds (Eutrochium Spp.) and Their Relatives,” n.d.
  2. “Eutrochium Purpureum (Gravel Weed, Indian Sage, Joe-Pye Weed, Marsh Milkweed, Motherwort, Pride of the Meadow, Purple Joe-Pye Weed, Sweet Joepyeweed) | North Carolina Extension Gardener Plant Toolbox.” Accessed October 20, 2024. https://plants.ces.ncsu.edu/plants/eutrochium-purpureum/.
  3. “Eutrochium Purpureum (Purple Joepyeweed) | Native Plants of North America.” Accessed October 20, 2024. https://www.wildflower.org/plants/result.php?id_plant=eupu21.
  4. “Minnesota Seasons – Common Eupithecia.” Accessed October 30, 2024. http://www.minnesotaseasons.com/Insects/common_eupithecia.html.
  5. Missouri Department of Conservation. “Plume Moths.” Accessed October 30, 2024. https://mdc.mo.gov/discover-nature/field-guide/plume-moths.
  6. Missouri Department of Conservation. “Three-Lined Flower Moth.” Accessed October 30, 2024. https://mdc.mo.gov/discover-nature/field-guide/three-lined-flower-moth.
  7. “Perigea Xanthioides.” In Wikipedia, January 8, 2023. https://en.wikipedia.org/w/index.php?title=Perigea_xanthioides&oldid=1132346411
  8. Holm, Heather. Pollinators of Native Plants:  Attract, Observe and Identify Pollinators and Beneficial Insects with Native Plants. Minnesota: Pollination Press LLC, 2014.
  9. “Species Phragmatobia Fuliginosa – Ruby Tiger Moth – Hodges#8156.” Accessed October 30, 2024. https://bugguide.net/node/view/41933.
  10. “Sweet Joe-Pye Weed (Eutrochium Purpureum).” Accessed October 20, 2024. https://www.illinoiswildflowers.info/savanna/plants/sw_joepye.htm.
Categories
native plants Pollinator gardening

A Wild and Wacky Plant

Clouds of beneficial wasps and small bees swarm the crown of tiny, white flowers.  Flowerheads rise on stalks up to nine feet tall offering stunning vertical accents in the garden.  This is Arnoglossum atriplicifolium one of several Arnoglossums native to Eastern North America.  

Why is this plant so different? The flowers don’t have any petals, only disk florets.  Disk florets usually make up the center of a bloom and are surrounded by ray florets or petals.

The leaves seem to defy description.  They’ve been called triangular or oval-cordate or oval but none of these is right.  The closest I’ve heard is Sycamore-like, with undulate edges (rippled edges).

The leaf texture is also unique.  Thick and shiny, it’s been compared to leather or plastic.  All these characteristics come together in a striking plant.2,6

Arnoglossum atriplicifolium grows in full sun to light shade.  Loamy, rocky or sandy soil are all acceptable.  But this plant loves evenly moist soil that stays constantly wet.  When Arnoglossum is happy, it reseeds freely.  Cut back the flower stalks to avoid this issue.1,6,9

In nature, Arnoglossum appears in open and rocky woodlands, thickets, wet meadows, along streams, in mesic forests, savannahs, woodland edges, sand dunes, rocky clearings in woodlands, prairies, meadows, upland woodlands, wooded slopes, slopes of ravines, sandy savannahs, sandy thickets, partly shaded thickets, and partly shaded banks near Lake Michigan.2,6

The first year, Arnoglossum atriplicifolium forms as a basal rosette of medium to dark green leaves.  These leaves grow up to eight inches long and six inches across.  While the top sides are green, the lower leaf surfaces are pale greenish white to bright white.  

In the second or third year, a stalk appears in Spring and grows to between three and nine feet tall with alternate leaves.  The unbranched stalk provides an erect accent in the garden.  These leaves become smaller as they go up the stalk.  Cavity nesting bees and wasps use the hollow stems for nesting.1,2,6,9

Flat-topped flowerheads (technically called a compound corymb) develop at the top of the plant stalk.  Without petals, the flowerhead make up their size by grouping four to fifteen florets together into corymbs.  These corymbs grow together to form the whole flowerhead.9  

The individual florets are about an eighth inch across and a third inch long with five disk florets.  Each one has a style that extends beyond its end.  The styles are bipartite which means two styles joined together.  As they mature, the tips curl away from each other forming circles.  Anthers also reach past the end of the floret.6

Arnoglossum atriplicifolium is self-incompatible.  Each floret must be fertilized with pollen from a different plant. Wasps, small bees and flies provide pollination.3

Blooms appear in mid-Summer and continue into early Fall.   Total flowering time is about one month.  Cut it back for a smaller second bloom.6

Adding to the overall wackiness of Arnoglossum, the most common visitors are predatory or parasitoid wasps.  Some of which look very scary indeed!  These wasps are also beneficial insects helping to control many garden pests.  In fact, the Xerces Society for Invertebrate Conservation labeled Arnoglossum as Supports Conservation Biological Control.

Wasps prefer dilute nectar on hot summer days and Arnoglossum is an excellent source of late season nectar.  The nectar secretes at the base of the style.  It’s drawn up the corolla so even short-tongued wasps.  White flowers keep the nectar cool and dilute.3

Thirty-four different species of wasps visit Arnoglossum atriplicifolium.4  These include, Sand Wasps (Bicyrtes spp.), Great Black Wasps (Sphex pensylvanicus), Great Golden Digger Wasps (Sphex ichneumoneus), Thread-Waisted Wasps (Ammophila spp.), Potter Wasps (Eumenes spp.), the Common Yellowjacket Wasp (Vespula spp.), and Grass-Carrying Wasps (Isodontia spp.).3

Are Yellowjackets beneficial?  It’s hard to feel that way.  They’re scary, the stings are painful, and they can ruin your picnic.  Vespids or Yellowjacket wasps can send you to the ER too, if you’re allergic to their sting.  So, is there an upside?

WARNING:  Yellowjacket or Vespid wasps form large colonies.  When disturbed, they’ll attack as a group.  Multiple stings are dangerous even to non-allergic individuals.

Do not allow nests around people, especially children, animals and especially those with allergies. Also, do not attempt nest removal yourself! Use a professional exterminator!

OK back to beneficial insects—Yellowjacket wasps build yearly nests.  Their mated queens overwinter in cozy spots like bumblebees.  In the Spring, the queens establish a nest and lay eggs to become workers.  The workers will continue building the nest and gathering prey.

Almost all Vespid wasps (Yellowjackets), use chewed wood pulp and saliva to create paper nests.  Different types of Vespids choose different locations for homes.  Options include holes like openings in trees, structural walls, abandoned animal burrows or rotting tree stumps or aerial places in trees or under building eaves.  Often nests aren’t noticed until they’re large or disturbed.11

But what good are they?  Colony size ranges from a few hundred to over 5,000.  Almost all these wasps hunt for insect prey and many prey on pests.  Depending on the species, Vespids target crickets, grasshoppers, spiders, flies, and fall webworms.  Those that live in trees and high places frequently gather food there.11

I wouldn’t let Yellowjacket set up housekeeping in my yard especially near children, animals, individuals allergic to bee stings or other human activity.  But you have a place on your property, where they won’t be disturbed, a Vespid nest is like a small army of pest control.

Many small bees gather nectar and pollen from Arnoglossum atriplicifolium.  Sweat Bees (Halictus sp. and Lasioglossum sp.) and small Carpenter Bees (Ceratina sp.) are some of the short-tongued bees seen.

Halictid or Sweat Bees fall in the small and mighty category of pollinators.  There are more than 500 species in North America.  In the garden and in natural area, they are more plentiful than most other native bees.7,8

Almost all are ground nesting but the colony structure can be solitary, communal, semi-social or eusocial.  Sometimes these nesting behaviors vary with time of year, location-geographic and altitude, and for reasons we don’t understand.5,7,8

Two fun facts about the Halictid bees are:  they drink human sweat and they can buzz pollinate.  Why do they lap up sweat?  It’s like an electrolyte drink for them.  On hot summer day, Halictid bees need some salt and other minerals.  Human perspiration is one easy source!5,7,8

What about buzz pollination?  Buzz pollination is sometimes called sonication.  A sweat bee holds onto a flower’s anther with its mandibles and curls its abdomen around the anther.  It vibrates its wing muscles to release pollen.5  

Many flowers need buzz pollination to effectively free their pollen.  These plants include the heath family (blueberry, cranberry) and nightshade (tomato, groundcherry, pepper, eggplant, potato),  A number of native bees can buzz pollinate, most famously, the Bumblebee.  Honeybees cannot.5,10

Lastly, flies gather nectar and pollen at Arnoglossum atriplicifolium.  Syrphid flies frequently stop to sip the accessible nectar.3

Bonus Bug: Both male and female mosquitos visit flowers for nectar. Females need blood for the protein and most use a sugar source. Males need a sugar source, like nectar, to survive. We don’t know how they choose particular flowers but they are attracted to some chemical compounds.12

Hope you enjoyed this look into a Wild and Wacky plant!  Arnoglossum atriplicifolium benefits some bizarre and wonderful insects as well as some more familiar ones.  It delivers a wonder accent in the garden and is an excellent source of late summer nectar!

Warm Regards,

Mary                            

References:

  1. “Arnoglossum Atriplicifolium – Plant Finder.” Accessed September 2, 2024 https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=293225.
  2. “Arnoglossum Atriplicifolium (Pale Indian Plantain) | North Carolina Extension Gardener Plant Toolbox.” Accessed September 2, 2024. https://plants.ces.ncsu.edu/plants/arnoglossum-atriplicifolium/.
  3. Holm, Heather. Pollinators of Native Plants:  Attract, Observe and Identify Pollinators and Beneficial Insects with Native Plants. Minnesota: Pollination Press LLC, 2014.
  4. Holm, Heather. Wasps:  Their Biology, Diversity, and Role as Beneficial Insects and Pollinators of Native Plants. Minnesota: Pollination Press LLC, 2021.
  5. Missouri Department of Conservation. “Halictid Bees (Sweat Bees).” Accessed September 2, 2024. https://mdc.mo.gov/discover-nature/field-guide/halictid-bees-sweat-bees.
  6. “Pale Indian Plantain (Arnoglossum Atriplicifolium).” Accessed September 2, 2024. https://www.illinoiswildflowers.info/savanna/plants/pale_indplant.htm.
  7. “SWEAT BEES: GENUS LASIOGLOSSUM | The Great Sunflower Project.” Accessed September 2, 2024. https://www.greatsunflower.org/Lasioglossum#.
  8. “Sweat or Halictid Bees.” Accessed September 2, 2024. https://entnemdept.ufl.edu/creatures/misc/bees/halictid_bees.htm#
  9. “Weird and Wonderful Plants for Pollinators: Pale Indian Plantain | Xerces Society.” Accessed September 1, 2024. https://xerces.org/blog/pale-indian-plantain.
  10. Xerces Society. “Delectable Native Plants Attract a Very Special Crowd.” Accessed September 2, 2024. https://xerces.org/blog/delectable-native-plants-attract-very-special-crowd.
  11. “Yellowjackets and Baldfaced Hornets | CALS.” Accessed September 2, 2024. https://cals.cornell.edu/new-york-state-integrated-pest-management/outreach-education/whats-bugging-you/bees-and-wasps/identifying-bees-and-wasps/yellowjackets-and-baldfaced-hornets
  12. “Not Just from Blood: Mosquito Nutrient Acquisition from Nectar Sources – ScienceDirect.” Accessed September 2, 2024. https://www.sciencedirect.com/science/article/pii/S1471492220300404#.
Categories
native plants Pollinator gardening

Ephemeral Purple Pinwheels

From late Spring to mid-Summer, the blue-purple flowers of Spiderwort decorate the morning garden.  These three petalled flowers offer pollen for pollinators and beneficial insects.  While the flowers fade by afternoon, the lovely blue-green foliage graces the garden throughout the bloom period. 

An adaptable plant, Tradescantia ohiensis thrives in acid-based, calcareous, limestone-based, sandy, sandy loam, medium loam and clay.  It prefers full or part sun and the whole range from wet to dry conditions.  The root system is not only fibrous but thick and fleshy.1

In natural settings, Spiderwort is widely scattered except in disturbed areas.  It can create sizable colonies in these areas.  Tradescantia ohiensis can be found in moist to mesic black soil prairies, sand prairies, thickets, limestone glades, woodland borders, Bur Oak savannas, sandy black oak savannas, roadside ditches, areas along railroads—including the ballast, and moist meadows near woods or rivers.1,3

The foliage of Tradescantia ohiensis is vase-shaped with soft blue-green color.  Its leaves wrap around the stems and then arch gently down narrowing to a point.  Leaves are up to 15” long and one inch wide at the base.  Stems are round.  Both leaves and stems are usually glabrous (smooth with no hair or down).1

The charming flowers have three petals, an unusual number and shape combined with their unusual color.  Blue is the rarest color bloom for native plants.  These two features add to the plants’ garden appeal.  

The top of the petals forms a rounded triangle.  Each bloom has six bright, yellow anthers and fine hairy filaments under the anthers.  The filaments are a slightly darker version of the flower color.1,3

To avoid self-pollination, the anthers release their pollen first.  Then they curve away from the style as it extends and becomes receptive.  Essentially, the anthers move any remaining pollen away from the stigma (area on the top of the style).4

As it spreads and multiplies in the garden, color variations appear.  In my garden, I have deep blue-purple flowers and blooms that are pale lavender with white centers.

The blossoms have unusual schedule.  Each morning one to a few buds open from each group.  They stay open until mid-day, sometimes longer on cloudy days.  Then they wither and fade.  All the buds finish by mid-summer.3  

At that time, cut the plants back to between six  and twelve inches.  This pruning increases chances of a second bloom and helps keep the plants tidy.3,5

In some climates, Spiderwort dies back completely after blooming.  This happens in my garden in the Great Lakes area.  I have fall plants that fill in the space.  This is similar to having perennials grow to cover where bulbs have faded.  In the past, I’ve also used planters in the bare spots.

Managing Tradescantia ohiensis can be a bit of a challenge.  In the garden, Spiderwort spreads easily to form large clumps.  It can also self-seed when conditions are right.  Sometimes considered a problem plant, Spiderwort is easily pulled.  

Deer, rabbits and other herbivores eat Tradescantia ohiensis especially in the early Spring.  I find this happens more when the plants are within the garden, away from foot traffic and people.  A good herbivore deterrent helps.1

Xerces Society for Invertebrate Conservation declares Spiderwort of Special Value to Native Bees, Special Value to Bumblebees and (it) Attracts Beneficial Insects.  Numerous bees, flies and beneficial insects visit these plants.  Its long bloom season provides a reliable pollen source for many weeks.  Bumblebees are primary pollinators for Tradescantia ohiensis.  

Bumblebees pollinate native and horticultural plants.  They’re even used in some commercial agricultural settings.  As a vital pollinator, I’ll be shining a spotlight on the lifecycle of one particular bumblebee–the Eastern Bumblebee (Bombus impatiens).6

Bumblebees fly from early spring through fall and need resources for all this time.  As generalists, they forage on many different flowers.  The Eastern Bumblebee (Bombus impatiens) is a common visitor to Tradescantia ohiensis.

Bumblebees are social bees, living and raising their young in colonies.  Colonies range from around 50 to hundreds of bees.  The life of the colony begins in the Fall.  Fertile female and male bumblebees hatch and go out to mate.  The males search for females from a different colony.

After mating, the gynes (inseminated females) forage for about two weeks building up fat stores to support them for the winter.  Then, they’ll look for a cozy place to overwinter.  The gynes often choose old rodent holes or they burrow a few inches underground.

In Spring, the gynes emerge when the soil warms and flowers begin blooming.  They search carefully for a nesting site.  Possible spots include old rodent holes, spaces between two rocks, deep thatch in grass, tufts of dead grass, old bird feeders, and unused sheds or barns.  The gyne looks for a sheltered, dry space for her colony.

I’ve followed several gynes in the Spring and I’ve yet to see one find her spot.  The gyne spend a lot of time landing and exploring each area until she finds the perfect one.

Once the nesting spot is chosen, she creates a honey pot.  The pot is made from wax secreted between her abdominal segments.  The gyne fills this with nectar she has collected.  

This nectar tides her over on cold, rainy Spring days when she can’t forage.  The mature colony will maintain several honey pots for similar weather conditions and for workers who remain in the colony and don’t forage.

At this point, the gyne begins collecting pollen.  She mixes the pollen with a little nectar and forms a ball.  Multiple fertile (female) eggs are laid on the ball.  Then she covers it with a wax coating.  

The foundress (a gyne who has established a nest) continues foraging.  When it is too cool to fly, she incubates her eggs by sitting on top of the wax and shivering.  The eggs hatch in three to five days.  If the foundress dies during this time, the larvae also die, and the nest will fail.

Once the eggs have become adult workers, the foundress at last becomes the queen.  Unlike honeybees, the queen continues to gather food and the workers help her with harvesting and with caring for the larva.  Also, unlike honeybees, workers can lay eggs.  The queen suppresses this behavior with pheromones or aggression.  If an egg  is laid, the queen destroys it.  

The colony life ends in late Summer or Fall.  Close to this time, the queen lays unfertilized eggs which become male bumblebees.  She also lays fertilized eggs that are feed additional pollen.  These eggs become next year’s gynes.6

While Bumblebees, honeybees and other long tongued bees pollinate Spiderwort, numerous small bees and flies visit the flowers.  The small bees include Sweat Bees (Lasioglossum spp.),

Green Sweat Bees (Agapostemon spp.),

small Carpenter bees (Ceratina),

Mason Bees (Osmia spp.), European Wool Carder bee (Anthidium maculatum).1,4

Both syrphid flies and bee flies are among the fly visitors.  I’ve mentioned syrphid flies in many posts.  Their larvae  consume huge numbers of aphids.  Today let’s shine a spotlight on the insects themselves.1,4

The names syrphid, hover or flower flies all mean the same group of insects—Syrphidae.  Most have yellow and black stripes that make them resemble bees or wasps.  Others are hairy with long thin abdomens.   They range from less than a quarter of an inch to more than three-quarters of an inch.  Their antennae are short.7

Adults seek out flowers for nectar and pollen.  They’re particularly attracted to tiny flowers.  Yarrow, wild mustard, fennel, coriander and sweet alyssum are all favorites.  

Reproduction usually centers around aphid colonies.  The female lays a single egg on a leaf near the colony.  She may produce hundreds of eggs throughout the growing season.

Eggs hatch into small, legless maggots varying in color from creamy-white to green to brown.  With a slug-like appears, they taper near the head.  The larvae mature in one to three weeks depending on the species, temperature, and amount of food. There are five to seven generation per year.  The final generation overwinters as pupae either on a leaf or in the soil.

These larvae are the beneficial insects.  A single larva can eat up to 400 aphids.  They effectively control aphids in a mixed plot or in a garden.  Although, syrphid fly larvae haven’t been studied commercially.

These larvae mostly hunt aphids.  They can also consume small caterpillars, thrips and other slow-moving insects.  In addition, syrphid fly larvae have been observed preying on small European corn borer and corn earworm larvae.7

Thank you so much for joining me for this long look at Spiderwort, Tradescantia ohiensis.  I hope you enjoyed the information on this beautiful and versatile plant and the spotlights  on the life cycle of the Eastern Bumblebee, Bombus impatiens, and the Syrphid flies.  

I’d love to answer questions or hear your stories!  Please let me know what’s going on in your garden!

Warm Regards,

Mary

References

  1. Hilty, J., n.d., Ohio Spiderwort, Tradescantia ohiensis, Dayflower family (Commelinaceae), http://www.illinoiswildflowers.info/prairie/plantx/oh_spiderwortx.htm
  2. No author, n. d., Tradescantia ohiensis, Ohio Spiderwort, Bluejacket, Commelinaceae, (Spiderwort Family), https://www.wildflower.org/plants/result.php?id_plant=TROH
  3. No author, n. d., Tradescantia ohiensis, Bluejacket; Ohio Spiderwort; Smooth Spiderwort, https://plants.ces.ncsu.edu/plants/tradescantia-ohiensis/
  4. Holm, H., 2014, Pollinator of Native Plants:  Attract, Observe and Identify Pollinators and Beneficial Insects with Native Plants, Pollination Press LLC., Minnesota
  5. No author, n. d., Tradescantia ohiensis,https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=279262&isprofile=1&basic=Tradescantia%20ohiensis
  6. Holm, Heather, 2017, Bees:  An Identification and Native Plant Forage Guide, Pollination Press LLC, Minnesota
  7. Mahr, Susan, n.d., Hover, Flower or Syrphid Flies (Syrphidae), https://hort.extension.wisc.edu/articles/hover-flower-or-syrphid-flies-syrphidae/#:~:text=Hover%20flies%20(or%20flower%20flies,the%20flowers%20and%20darting%20around.
Categories
native plants Pollinator gardening

A Summer Cornucopia

Part 2

And we’re back for Part II of The Summer Cornucopia!  Today the focus is on insects and how they use Common Milkweed.  If you missed Part I and are interested in the plant and pollination, here’s a link: https://wordpress.com/post/wildthingsinthe.garden/1831.

Asclepias syriaca draws an abundance of insects.  The sap, leaves and flowers are all used for food while blooms provide nectar to many insects.  Common Milkweed supports different life stages of flies, wasps, bees, butterflies, moths, skippers, plant bugs and beneficial insects.  Even hummingbirds try to sip nectar although they can’t reach it.1,7  

The most famous visitor to Common Milkweed is the Monarch butterfly (Danaus plexippus).  Monarchs can only use milkweeds (Asclepias) to feed their caterpillars. Growing milkweed supports the generations of Monarchs that hatch over the summer months.  When the last summer generation is born and transforms into an adult, they’ll drink nectar from milkweed and other flowers for food and fuel for their migration.8  

Growing native milkweeds helps preserve the existing Monarch population.  If you’re interested in helping Monarchs, Monarch Watch has excellent information on creating Monarch Waystations at https://www.monarchwatch.org/waystations/ .  Here are the highlights of the plan!8

How big does a waystation have to be?  Any size will help the Monarchs (and other pollinators!).  If possible, a 100 square foot waystation is highly effective.  The area doesn’t have to be all in one spot.  There can be several plantings throughout a property.

Sun is important for Monarchs.  Like other insects, they need heat and sunlight to warm themselves for flying and daily activities.  An area with six or more hours of sunlight is required.  Coincidentally, most milkweeds thrive under those conditions.

Milkweed also grow well in well-drained soil.  Place Monarch Waystations in low clay areas with fast draining soils.

Place plants close together (although not closer than recommended).  Monarchs and their caterpillars need shelter and protection from predators and the weather.

What about milkweed?  At least ten plants are recommended preferably with two or more types of milkweeds.  This planting scheme gives an extended season of bloom and allows the Monarchs longer access to the milkweed plants and nectar.  One type of milkweed is okay if more than ten plants are included.

Establish continuous supply of nectar plants.  Use annual, biennial and perennial plants.  Native plants are a great choice.  These plants also benefit the other pollinators.

Finally, create a management plan.  How will the waystation be maintained?  The plan contains basic garden maintenance:  mulching, fertilizing, removing invasive plants.  Additionally, it includes Monarch specific items:  eliminate insecticides, add more features like a water source or puddling spot.

Again, for more information on Monarch Waystations and other resources, including free milkweed programs, go to https://www.monarchwatch.org/waystations/

In addition to Monarchs, swallowtails (Papilio), fritillaries (Speyeria), viceroy butterflies (Limenitis), sulfurs (Pieris), and other butterflies also visit Asclepias syriaca.  Skippers use Asclepias syriaca for nectar including Ancyloxipha.1,7  

Common Milkweed is a larval host for the striking Milkweed Tussock Moth (Euchaetes egle) caterpillar, the Unexpected Cycnla (Cycnia inopinates) and the Delicate Cycnia (Cycnia tenera).  All are part of the group Artiinae or Tiger Moths.1  

The Delicate Cycnia (Cycnia tenera) lacks the usual aposematic coloration  It has a soft tan larva and a charming white adult with just a touch of orange on the head and wing edges.  Instead, it emits aposematic ultrasound calls when caught!  Bats release their prey when they hear the calls.  During the day, their color variation seems to keep birds away.1,9

Both long-tongued and short-tongued bees visit Common Milkweed for nectar.  These include honeybees (Apis),

Bumble Bees (Bombus),

leaf-cutter bees (Megachile),

cuckoo bees (Coelioxys), small carpenter bees (Ceratina)

and sweat bees (Halictus and Lasioglossum).1,7,10

Many wasps enjoy nectaring at Milkweed flowers especially Sphex, Tachytes, Polistes,  Myzinum, and ichneumon wasps.  Sphex ichneumoneus is a known pollinator of Common Milkweed.1,7

Numerous beneficial insects visit Asclepias syriaca including the delicate and diverse ichneumon wasps.  The adult wasps use milkweeds’ nectar for fuel while searching for insect prey.  They’re considered parasitoids and the females lay eggs inside grubs and caterpillars.  

Young of boll weevils, tomato hornworms and wood borers are all food for ichneumon wasps.  In addition to garden pests, adults hunt large insects such as spiders and butterflies.  

In general, ichneumon wasps help reduce the number of insects that reach reproductive age.  Many of these prey insects damage trees.  In this way, the wasps help keep trees healthy.11

Bembix americana, a predatory sand wasp, also gathers nectar from Common Milkweed.  B. americanafeeds their young true flies (Diptera).  Diptera include house flies, gnats and mosquitos.  

As populations of flies increase, B. americanas numbers rise.  A single larvae can eat two dozen flies.  B. americana uses a different strategy for provisioning its young.  Other wasps paralyze their prey and stock each cell with the required (living but paralyzed) insects.  This sand wasp kills the flies and adds more food as needed.12

Asclepias syriaca hosts predatory stink bug larvae.  Stink bugs have a terrible reputation especially since the arrival of  the invasive Brown Marmorated Stink Bug.  But predatory stink bugs are a whole different category.  These are beneficial insects that hunt insect prey.  

Above, is a photo of a Spined Soldier Bug larvae on milkweed.  There are five larval stages (instars) and all eat insects.  Their preferred foods include Mexican bean beetle, Colorado potato beetle, and imported cabbageworm.  

Look for the adult Spined Soldier Bug on plants where prey may be located.  These plants include the melons/squash/cucumber (cucurbit), broccoli, cauliflower, kale, etc. (cruciferous) and tomatoes, peppers, eggplant (solanaceous) crops.  

If you’re looking for eggs, they’re an incredible metallic bronze color with a row of spines like a crown.  Just hatched larvae, cluster around the eggs eating necessary bacteria.  Spined Soldier Bug can be purchased commercially.13

In addition to all these, Asclepius syriaca hosts many beetles and bugs,

grasshoppers,

and leafhoppers

Finally, flies, including beneficial ones, nectar on Asclepius syriaca.

I hope you’ve enjoyed this exploration of the insects found on Common Milkweed.  Pollinators and beneficials all enjoy Asclepias.  It’s always worth stopping to see who’s home in the milkweed patch with or without flowers!

Happy Gardening, Mary

References

  1. Hilty, J., n.d., Common Milkweed, Asclepias syriaca, Milkweed family, (Asclepiadaceae),  https://www.illinoiswildflowers.info/weeds/plants/cm_milkweed.html
  2. Berkov, A., 28.October.2010, Plant Talk:  Inside the New York Botanical Garden; Plant Profile:  The Extraordinary Common Milkweed, How Do Insects Feed on this Plant with Sticky White Latex? https://www.nybg.org/blogs/plant-talk/2010/10/science/plant-profile-the-extraordinary-common-milkweed/#:~:text=Plants%20in%20the%20genus%20Asclepias,Asklepios%2C%20the%20ancient%20Greek%20physician.
  3. Bowe, Scott, 11.September.2018, Milkweed is More Than Just a Common Weed, WXPR, https://www.wxpr.org/natural-resources/2018-09-11/milkweed-is-more-than-just-a-common-weed
  4. Nelson, M. and Alfuth, D., 24.February.2021, Milkweed (Ornamental Plants Toxic to Animals), X-number:  XHT1276, https://hort.extension.wisc.edu/articles/milkweed-ornamental-plants-toxic-to-animals/
  5. Taylor, David, n.d., Common Milkweed, (Asclepias syriaca L.), Plant of the Week, https://www.fs.usda.gov/wildflowers/plant-of-the-week/asclepias_syriaca.shtml
  6. Eldredge, E.P., 2015,11,00, Milkweed Pollination Biology, Plant Materials Technical Note NV-58, Natural Resources Conservation Service, https://www.nrcs.usda.gov/plantmaterials/nvpmctn12764.pdf
  7. Betz, R.F., Struven, R.D., Wall, J.E. & Heitler, F.B., 1994, Insect Pollinators 12 Milkweed (Asclepias) Species, T.B. Bragg and J. Stubbendieck (eds.) Proc. Of the Thirteenth North American Prairie Conference. Univ. of Nebraska, Lincoln, NE.
  8. No author, n.d., Monarch Waystation Program, https://monarchwatch.org/waystations/
  9. Geere, Duncan, 2010. August.19, Tiger Moths Scare Bats with Ultrasonic Clicks, Wired, https://www.wired.com/2010/08/moth-jamming/
  10. Holm, Heather, 2017, Bees:  An Identification and Native Plant Forage Guide, Pollination Press LLC
  11. No author, n.d., Ichneumon Wasps, Discover Nature>Field Guide:  Missouri Department of Conservation, https://mdc.mo.gov/discover-nature/field-guide/ichneumon-wasps
  12. No author, n.d., Sand Wasps, Discover Nature>Field Guide:  Missouri Department of Conservation, https://mdc.mo.gov/discover-nature/field-guide/sand-wasps
  13. Berish, Chelsea, n.d., Spined Soldier Bug in Kentucky, ENTFACT-325: SPINED SOLDIER BUG IN KENTUCKY, University of Kentucky Department of Entomology, Martin Gatton College of Agriculture, Food and Environment
Categories
native plants Pollinator gardening

A Summer Cornucopia

Common Milkweed or Asclepias syriaca is a superb Monarch support and a mainstay of Monarch waystations.  But it is so much more.  This plant feeds more than 450 insects at different life stages. Diverse insects consume nectar, sap, leaves, flowers and seeds5.  Admittedly weedy, its lovely blooms are fragrant and enhance any scent garden1,5.

Common Milkweed thrives in full sun and well-drained soils.  Like other “weeds”, it’s not picky about growing conditions.  A. syriaca  grows in clayey, sandy or rocky calcareous soils, loamy soils and high clay or sand soils. 

Asclepias syriaca springs up in disrupted areas.  Human activity disrupts natural areas.  But natural disruptions occur where water rises and falls, for example, along streams and lakes.  

In nature, Common Milkweed is found in moist and dry black soil prairies, sand prairies, sand dunes along lake shores, fields, pastures, abandoned fields, vacant lots and along railroads, fence rows and roadsides. 

Common Milkweed absolutely lives up to its weedy name.  It spreads by seed and by long creeping rhizomes that pop up in unexpected places.  Once established, this plant is extremely difficult to remove. 

These habits are offset by Common Milkweed’s value to insects and pollinators.  It’s best to let it grow where you don’t mind its vigorous and abundant nature—a wild area, a meadow or a prairie garden.

Asclepias syriaca offers a strong erect form in the garden.  The pale, cylindrical central stem supports opposite jade-green leaves.  These leaves range from pale to dark green on top and are pale green with short, dense hair underneath.  Each leaf has a distinctive central vein with small veins spreading to the edges.  

The milky sap, which gives Milkweed its name, oozes whenever part of the plant is broken.  The sap is called a latex and contains 2% latex.  The latex is thick and sticky.  

Most ingeniously, caterpillars will reduce the sap’s flow by taking tiny bites closer to the stem.  The sap leaks out there.  When the caterpillar begins to eat a leaf, there’s less latex at the feeding site.  Thus, less chance the sticky stuff will foul the larva’s mouth2,3.

For humans and other mammals, there are other concerns.  The milky sap contains cardenolides, specifically cardiac glycosides.  Contact with the skin or eyes causes irritation.  If eaten or exposed to mucous membranes, cardiac glycosides can disrupt the nervous system, the kidneys, the muscles (which includes the heart) and the human’s/animal’s acid/base balance3,4,5.  

The monarch and other insects that consume milkweed have turned this to their advantage.  As the caterpillars/insects consume milkweed their bodies store the cardiac glycosides.  If a bird or animal eats them, they taste bitter and can make the predator feel sick.  

Predators soon learn to leave them alone. The orange/black or red/black coloring of milkweed insects signals, “Stay away!  Not good for you!”  The technical term for this warning coloration is ‘aposematic’5.

Milkweed blooms don’t dazzle but flower in 1930’s vintage shades.  The drooping balls of florets are soft and dusky lasting one to one and a half months.  Colors range from greenish white to greenish pink to rosy-pink to purplish-pink to reddish purple.  

Each cluster averages 30 individual florets but can have up to 100. Their sweet, vanilla fragrance drifts from the three to five umbels on each plant.  

Up close, each floret is a fascinating feat of engineering all directed toward an exceptional pollination system.  Each a quarter of an inch across, the florets have five reflexed (bent back) petals and five raised hoods with curved horns.  The hoods have lighter colors than the petals.  

In the center of each floret, is a cylindrical structure formed by two fused stigmas.  It’s called the stigmatic column.  

Between the hoods, are the stigmatic slits.  These slits hold the pollinaria.  Unique structures, pollinaria hold waxy sacs of pollen.  These are transferred instead of the loose, powdery pollen used by most flowers.  Milkweeds and orchids are the only known plants to have them6,7.

The milkweed pollinium (or pollinarium) consist of a blackish-brown oval gland (corpusculum) with a slit, two translator arms hanging from the gland and two pollinial sacs.  Before each sac, a knee bend of approximately 900 occurs in the arm.  This bend enables the rotation of each sac during pollination.

In the milkweeds, the pollinial sac sit inside the stigmatic column and only the corpusculum is visible between the hood structures.  When an insect lands on the flower, one of its legs may slip into the stigmatic slit between two hoods.   As it tries to free itself, the leg moves upward toward the slit in the corpusculum. Bristles in the chamber keep it from going back down.  

Insects must be strong to free themselves.  Large butterflies, predatory wasps and long tongue bees are most likely to remove pollinaria.  Lost legs and dead smaller insects both occur from failed escape attempts.

When a pollinaria is removed, it begins to dry.  The pollinial sacs rotate 90o during drying.  The rotation moves them into the correct position for pollination.  

When the insect lands on another milkweed,  the knee bend (not the corpusculum oval) slides into the space between the hood petals.  The translator arm follows then the rotated pollinial sac.  The pollinial sac slides into a space in the stigmatic column and pollination is completed.  

When the insect continues pulling upward, the translator arm breaks.  The insect keeps the remaining part of the pollinaria.  

It’s also possible to start a chain of pollinaria during this process.  As the broken translator arm slides between the hoods, it can hook the corpusculum slit of this floret’s pollinaria adding a fresh pollinaria to the partial remaining one.  Clumps and chains of all sorts develop this way.  These groups of pollinaria may increase chances of pollination6.7.

Part I, ends here, with the exciting conclusion of a fertilized milkweed.  Part II will continue with photos and information about the insects that use Common Milkweed.  What a crowd it is—including flies, wasps, bees, butterflies, moths, skippers, plant bugs and beneficial insects!

See you next time to discover what Wild Things are in the Garden!

Mary

References

  1. Hilty, J., n.d., Common Milkweed, Asclepias syriaca, Milkweed family, (Asclepiadaceae),  https://www.illinoiswildflowers.info/weeds/plants/cm_milkweed.html
  2. Berkov, A., 28.October.2010, Plant Talk:  Inside the New York Botanical Garden; Plant Profile:  The Extraordinary Common Milkweed, How Do Insects Feed on this Plant with Sticky White Latex? https://www.nybg.org/blogs/plant-talk/2010/10/science/plant-profile-the-extraordinary-common-milkweed/#:~:text=Plants%20in%20the%20genus%20Asclepias,Asklepios%2C%20the%20ancient%20Greek%20physician.
  3. Bowe, Scott, 11.September.2018, Milkweed is More Than Just a Common Weed, WXPR, https://www.wxpr.org/natural-resources/2018-09-11/milkweed-is-more-than-just-a-common-weed
  4. Nelson, M. and Alfuth, D., 24.February.2021, Milkweed (Ornamental Plants Toxic to Animals), X-number:  XHT1276, https://hort.extension.wisc.edu/articles/milkweed-ornamental-plants-toxic-to-animals/
  5. Taylor, David, n.d., Common Milkweed, (Asclepias syriaca L.), Plant of the Week, https://www.fs.usda.gov/wildflowers/plant-of-the-week/asclepias_syriaca.shtml
  6. Eldredge, E.P., 2015,11,00, Milkweed Pollination Biology, Plant Materials Technical Note NV-58, Natural Resources Conservation Service, https://www.nrcs.usda.gov/plantmaterials/nvpmctn12764.pdf
  7. Betz, R.F., Struven, R.D., Wall, J.E. & Heitler, F.B., 1994, Insect Pollinators 12 Milkweed (Asclepias) Species, T.B. Bragg and J. Stubbendieck (eds.) Proc. Of the Thirteenth North American Prairie Conference. Univ. of Nebraska, Lincoln, NE.

Categories
Pollinator gardening

A Froth of White

In late Spring, the parasol blooms of Yarrow (Achillea millefolium) open.  The intricate creamy-white flowerheads draw every type of pollinator offering nectar and pollen to active insects.  An assortment of caterpillars nibble on its stem, leaves, and flowers.

While yarrow grows in a range of habitats, it prefers full or part sun and medium to dry soils.  It’s not picky about soil type if the soils are well drained.  Yarrow likes disturbed areas.  In nature, soil disturbances happens where water rises or falls (for example, lakes and rivers) and where large animals gather (such as, at a watering hole).  Humans, of course, add to land disturbance.  Habitats with yarrow include medium to dry prairies, pastures, unused fields, grassy waste areas, and edges of paths, yards, or hedges.1,2

Like so many native plants, yarrow reseeds freely when happy.  You can limit this by cutting off seedheads and weeding out seedlings.  Its seedlings are distinctive with their delicate, lacy foliage. Beware the rhizomes.  Yarrow can form large colonies from spreading rhizomes.  Root prune a clump with a sharp shovel or pull the shoots to keep it in check.

Achillea millefolium is all about multiples with compound flowers and doubly divided leaves.  The elaborate, ruffled “flowerheads” are held on single stems.  What looks a flowerhead is really a group of smaller flower heads called pedicels.  These pedicels together form a compound corymb and that’s what we see as a flower.  Yarrow’s corymbs can have 150 to 200+ individual florets! (Arkansas native plant society)  Each floret is about of a quarter inch across and has ray and disk parts.  It has three to eight ray florets around the edge and six to forty disk florets in the center.  Florets begin opening in May and can last as late as August.1,2,3.4.5

Yarrow’s foliage adds a fine, lacy note to the garden.  It ranges from pale to medium green.  The leaves are approximately six inches long and one inch wide becoming smaller toward the top of the stem.  Their overall outline is elliptical but each pointed leaf is divided and subdivided.  Leaflets and sub-leaflets curve and turn in different directions creating a soft and delicate appearance.  The sessile (leaves touch the stem) or almost sessile leaves grow in a spiral along the stem.  They can have fine hairs or be smooth.

Achillea millefolium is listed as native and introduced in most of the United States.4  It’s also called a species complex not a species.  But what does that mean?  Let’s talk about why this yarrow is so diverse and, briefly, what is says about the classification system.  If that doesn’t interest you, please skip down to the section labeled POLLINATORS.

Part of Yarrow’s story stems from a long history of human use going back thousands of years.  Yarrow’s been found in Neanderthal burial sites dating back as far as 65,000 years.  Although it probably originated in Asia, peoples in Europe, the Americas and Asia have used it for millennia.  Like any useful plant, it was transported and planted wherever people went.  So now we have Yarrow in Asia, throughout Europe, throughout the Americas, as well as on distant islands like Greenland, Patagonia, New Zealand, and Hawaii.

To make matters more difficult, Achillea millefolium is complicated genetically.  It adapts expertly to different environments and so changes its genes.  Yarrow is also one of many plants that can increase its number of genes.  For instances, humans have two sets of genes or are diploid.  Yarrow can double that-tetraploid and sometimes add one more set-hexaploid and again-octoploid.  All those variations can successfully breed together producing more Achillea millefolium.  (Animals with different polyploidy can’t usually breed together.)  All this genetic diversity doesn’t change the appearance very much—some are taller or shorter or have more petals (ray flower) or less.  It does matter to the insects that use Yarrow either.

The species complex designation allows for one species with a lot of diversity in morphology (physical characteristics) and genetics.  It acknowledges that those differences aren’t enough to indicate separate species.  

So, what does this have to do with native plants and pollinators?  Only that, things are sometime more complicated than they seem.  Botanists trying to classify plants are applying human rules to a system not controlled by humans.  This blog (https://khkeeler.blogspot.com/2014/04/plant-story-yarrow-achillea-millefolium.html) is a great read by a botanist about Yarrow’s history and botanical classification.

POLLINATORS

Achillea millefolium cannot pollinate itself and relies on insects.  The Pollinator Program at The Xerces Society for Invertebrate Conservation declared it Supports Conservation Biological Control and of Special Value to Native Bees.  The Biological Control designations means it provides resource to beneficial insects. Its visitors include bees, wasps, beetles, butterflies, moths, true bugs, and others.1

All parts of Achillea millefolium have a distinct scent.  It’s been described as resinous, like fresh pine needles, a combination of chamomile and thyme, a mixture of rosemary, oregano, and other cooking herbs and, finally, soapy and astringent.  All these descriptions hint at how different people perceive smells but none of them mention sweet or flowery.  The fragrance of a plant or flower affects which pollinators it attracts.  Generally, more savory ranging to rotting odors attract flies and beetles.  Information about yarrow mentions many different flies visiting the flowers.6

In my garden, I see many small bees gathering pollen and nectar.  Ceratina (small carpenter bee), Lasioglossum (small sweat bee), Megachile (leafcutter bee), Andrena (mining bee), and Nomada (cuckoo bee) collect resources on Yarrow.  These small bees visit the flowers throughout the summer.  Even when the Yarrow flowerheads seem finished, bees continue to visit harvesting every last bit of pollen and nectar.

Beneficial insects enjoy Achillea millefolium throughout the blooming season.  Green lace wings, lady beetles, and a variety of flies harvest resources on Yarrow.  The flies include bee flies (Bombyliidae), soldier flies (Stratiomyidae), Syrphid flies,  Tachinid flies, thick-headed flies (Conopidae), flesh flies (Sarcophagidae), blow flies (Calliphoridae), Muscid flies, and Anthomyiid flies.

Adult bee flies gather nectar while their larvae act as beneficial insects.  This is Villa lateralis.  Specific studies of V. lateralis are difficult to find.  However, several species of Villa destroy grasshopper eggs in the larva stage.  Others parasitize caterpillars.8

Butterflies and moths use Yarrow as well.  Numerous butterflies nectar at the flowers including blue copper butterflies (Lycaena heteronea heteronea).  Achillea millefolium is a larval host for many moth species. Some eat the leaves while others bore through its stem or feed on the flowerhead.  Papaipema nebris (Stalk borer Moth) is a stem borer.  Flower eaters include Chlorochlamys chloroleucaria (Blackberry Looper Moth), Eupithecia absinthiata (Wormwood Pug), Eupithecia miserulata (Common Pug), Synchlora aerate (Wavy-lined Emerald), Heliothis phloxiphaga (Darker-spotted Straw), and Depressaria alienella (no common name).  Moths and a butterfly that feed on leaves include the American Painted Lady (Vanessa virginiensis), Agrotis volubilis
(Voluble Dart), Cryptocala acadiensis (Catocaline Dart), Lacinipolia olivacea (Olive Arches), Orthodes cynica (Cynical Quaker), Paradiarsia littoralis (Labrador Dart), Pseudorthodes vecors (Small Brown Quaker), Trichordestra legitima (Striped Garden Caterpillar) and Gillmeria pallidactyla (Yarrow Plume Moth).

I hope you enjoyed this journey into Achillea millefolium or Yarrow.  If you don’t have it in your garden, take a look at it in nature.  See who’s visiting those adaptable plants that have traveled so far!

Bye now,

Mary



REFERENCES:

Categories
Pollinator gardening

A Dynamic Duo for Spring,

New Year’s has past, plants and pollinators are sleeping but gardeners dream of flowers and foliage!  Today, I’ll talk about two of the first native plants to bloom in my garden.  Together they blossom from early spring to early summer.  They support emerging beneficial insects and pollinators including early queen bumblebees and native bee queens starting their nests.  In addition, these versatile plants thrive under a variety of conditions even green roofs!

In my garden, Spring starts with Round-leaved Ragwort (Packera obovata), also called Round-leaved groundsel.  Round-leaved Ragwort blooms as early as April and can continue until June.  The petite, yellow flowers are half to three-quarters inch in diameter.  They develop on  one- to two-foot-tall stalks, arranged in flat-topped clusters called corymbs.

After blossoming, Packera obovata keeps its basal rosette.  This smooth, medium green foliage has three-to-six-inch leaves.  The leaves are round to oval and serrated and remain throughout the growing season.

Round-leaved Ragwort enjoys full to part sun and dry to average soil moisture.  It’s not picky about soils and will grow in loam, sand, or rocky material.  Ragwort doesn’t like to have its feet wet and won’t thrive in rain gardens.

I’ve used this plant in my home garden and in the public garden where I volunteer. It is tremendously tough and easily outcompetes weeds–spreading by both rhizomes and abundant seeds.  It can be a nuisance plant because of its competitive nature.  

In the public garden, I’ve declared a truce with the Packera obovata.  We’re using it as a living mulch.  Packera easily withstands the light foot traffic we have on our mulched areas.  In the beds, we hope it shades out the invasive weeds but doesn’t interfere with the actual plantings.  Packera overpowers some native plants.  If you do try it as a living mulch, be aware you may need to remove it near slower growing plants.

Loads of pollinators visit Round-leaved Ragwort blooms1,2.  Numerous Halictid sweat bees use it including Augochlorella spp., Halictus spp., and Lasioglossum spp.  The Andrenid mining bee visitors include a specialist pollinator or oligolege.  An oligolege requires a particular plant or group of plants for its food source.  Andrena gardineri needs flowers in the Packera spp. for its food.  Various cuckoo bees, including Nomada spp., also use this plant.

Beneficial insects also use Packera obovata.  Adult Syrphid flies feed on nectar and pollen.  Their larval eat insect pests such as aphids.  Tachinid flies also visit this Packera.  Tachinid flies lay their eggs near, on or in caterpillars and adult and larval beetles.  The eggs hatch and the maggots consume the target insect.

Butterflies, skippers and moths nectar at Round-leaved Ragwort.  It also supports the caterpillar of the Northern Metalmark butterflies (Calephelis borealis).  This butterfly is considered very rare or local throughout its range.

Packera obovata isn’t recommended in pastures.  It’s toxic to almost all grazing animals.  The only exception is sheep who don’t seem to be as sensitive.

Shortly before Ragwort finishes bloom, Hairy Beardtongue, Penstemon hirsutus begins. The name Penstemon means five stamens and hirsutus means hairy.  Hairy Beardtongue has four fertile stamens and a fifth, infertile, hairy stamen–hence the name “Hairy”.  

This charming plant has dainty stalks of lavender and white tubular blossoms.  Its blooms are lipped and about an inch long.  Unlike its relative Penstemon digitalis, Penstemon hirsutus’  flowers are almost closed. The one- to two-foot stalks make a lovely contrast to Ragwort’s golden sunbursts. This flower stem can be windblown and needs support.

Hairy Beardtongue’s leaves are medium-green and lanceolate. The stem pierces the paired leaves which are two to three inches long. When the blossoms are spent, trim it back to healthy lower leaves and Beardtongue may rebloom. 

This Beardtongue grows in full sun to full shade.  I find that plants in partial shade are more likely to rebloom.  It enjoys dry to average conditions and well-drained sand to loam.  Hairy Beardtongue grows naturally in dry woodlands and open fields.

One caution with this plant, it does not grow or spread aggressively. It looks lovely blooming with the Ragwort but cannot compete with it. Years ago, I  planted them together and lost my Hairy Beardtongue.  The Round-leaved Ragwort completely overran it. Now, I clear a circle around each grouping of the Beardtongue to give it some breathing room. It’s a bit of extra work but I do enjoy them.

Hairy Beardtongue serves numerous pollinator while in bloom. The Pollinator Program at The Xerces Society of Invertebrate Conservation recognized it to be of Special Value to Native Bees and Special Value to Bumble Bees3. The flower structure encourages pollinators to enter and also helps complete pollination.  The extended lower lip offers a sturdy landing pad, an area to move and rest for the bees.  Penstemons as a group often have hairs inside the lower petals that urge the insect forward.  Penstemon hirsutus has these.  In addition, some penstemons have hook-like structures that give a light squeeze.  As the bee wiggles, the anthers wrap around it and transfer pollen.  This pollen sticks to where the bee’s body is most likely to touch the stamen and fertilize it.  Amazing how all these parts work together!4

Hairy Beardtongue draws a variety of pollinators5,6.  The tubular flowers attract creatures with long tongues such as Hummingbirds and long-tongued bees. Long-tongued bees include bumblebees (Bombus spp.).  Digger bees (Anthophora spp.), Long-Horned bees (Synhalonia spp.), Wool-carder bees (Anthidium manicatum), Mason bees (Osmia spp.), Melecta thoracica (a cleptoparasite) and Leaf-cutter bees (Megachile spp.) also visit these blossoms.

Short-tongued bees and small bees have found ways to use the food in Penstemon hirsutus.  Some small solitary bees, including sweat bees like Lasioglossum spp., simply crawl into the flower and collect its resources.  A small carpenter bee, Ceratina spp., is one of the main pollinators of Hairy Beardtongue.  Another small bee is Hoplitis spp., a small Mason bee.

Wasps and some large bees steal nectar.  Large carpenter bees (Xylocopa spp.) chew a hole at the base of the flower and drink nectar from the nectaries.  Nectar stealing doesn’t pollinate the plant but does provide the insect with food.

Several beneficial insects visit Hairy Beardtongue while it is blooming.  All of them use its nectar for fuel while going about their work.  Chalcidoidea is a group of small wasps.  They control both agricultural and natural pests.  Orius insidiosus or the Insidious Flower Bug or the Minute Pirate Bug hunts soft-bodied insects including spider mites, aphids, and thrips.  Braconidae are a family of parasitic wasp that prey on soft-bodied insects including aphids.  They also parasitize agricultural pests and caterpillars including the Tomato Horn Worm!  Aeolothripidae are thrips but predatory thrips.  They usually hunt small, soft-bodied insects.  Cynipoidea are parasitic wasps.  Empididae are predatory flies sometimes called dagger flies.

For readers looking for a new adventure, both Packera obovata and Penstemon hirsutus grow on green roofs!  Both grow well in the Midwest.  In Kansas, a trial tested a plot of the standard mixed sedums against a plot of sedums and grasses and a one of Packera obovata, other native plants and grasses.  Both mixed plots outperformed the sedums throughout the two-year trial7.

Chicago Botanic Garden studied the performance of a mix of native and non-native plants on green roofs.  Penstemon hirsutus received a five-star rating.  It established early and was healthy throughout the trial.  Its flowering was excellent, reseeding moderate and was only mildly affected by heat and drought.  Chicago Botanic Garden also observed both birds and a variety of insects on their roofs.  The insects included bees, butterflies, ants and more.  In addition to visiting mallard ducks, robins, sparrows, swallows, hummingbirds, and mourning doves, killdeer nested on the roof every year8.

Another study examined genetic diversity and pollen movement between urban green roof populations of Penstemon hirsutus.  The results showed that twenty-five percent of the plants were pollinated by plants on different roofs.  The authors found these green roofs contributed significantly to connection between the scattered populations.  Using native plants on green roof, is an interesting idea and new exciting new way add to contribute to native habit9.

I hope you enjoyed your trip through my Spring garden.  I’d love to hear about your garden or any questions you have!  Please contact me through the contact page with your stories and questions.

Mary

References:

  1. Hilty, J., n.d., Spoon-Leaved Ragwort, illinoiswildflowers.info, https://www.illinoiswildflowers.info/savanna/plants/rl_ragwort.html#:~:text=One%20bee%20species%2C%20Andrena%20gardineri,(ragworts).
  2. No author, n.d., Round-leaved Ragwort, https://www.canr.msu.edu/nativeplants/plant_facts/round_leaved_ragwort
  3. No author, n.d., Penstemon hirsutus, Lady Bird Johnson Wildflower Center, https://www.wildflower.org/plants/result.php?id_plant=PEHI
  4. Wheeler, Justin, 06/08/2017, Plants for Pollinators: Beardtongue, https://www.xerces.org/blog/plants-for-pollinators-beardtongue
  5. Hilty, J., n.d., Flower-Visiting Insects of Hairy Penstemon, https://www.illinoiswildflowers.info/flower_insects/plants/hry_penstemon.htm
  6. No author, n.d., Penstemon, Hairy Beardtongue, https://www.canr.msu.edu/nativeplants/plant_facts/penstemon_hairy_beardtongue#:~:text=Pollinators%20attracted,carpenter%20bees%2C%20and%20bumble%20bees.
  7. Decker, A. & Skabelund, L.R., 11/8-11/2021, Investigating the Effect of Substrate Type and Species Mix on Plant Cover on a Manhattan, Kansas Green Roof, Cities Alive Virtual conference, https://www.k-state.edu/greenroofs/images/pdf_docs/CitiesAlive%20Research_Paper_Sep2021_Decker_Skabelund.pdf
  8. Hawke, Richard, 2015, An Evaluation Study of Plant for Use on Green Roofs, Plant Evaluation Notes Issue, (38)2015, https://www.chicagobotanic.org/downloads/planteval_notes/no38_greenroofplants.pdf
  9. Ksiazek-Mikenas, K., Fant, J.B., & Skogen, K.A., 08/07/2019, Pollinator-Mediated Gene Flow Connects Green Roof Populations Across the Urban Matrix: A Paternity Analysis of the Self-Compatible Form Penstemon hirsutus, Frontiers in Ecology and Evolution, (7)2019, https://www.frontiersin.org/articles/10.3389/fevo.2019.00299/full#:~:text=Genetic%20Diversity%20of%20Green%20Roof%20vs.&text=The%20natural%20prairie%20populations%20of,genetic%20diversity%20(Table%202).