Bloodroot

In spite of the weather whiplash we’ve experienced since late February, spring wildflowers are slowly, cautiously beginning to emerge and bloom.  One of the first spring blossoms I saw this season was Bloodroot (Sanguinaria canadensis).

Bloodroot (Sanguinaria canadensis)

The sight of this stunning white blossom holding its face up to the sun was especially welcome after a snowy, chilly March.

With each sunny day more flower shoots make their way through their winter blanket of fallen leaves.  As Bloodroot emerges, it leads with a flower stem, each one wrapped by a single leaf.

Bloodroot (Sanguinaria canadensis) emerging from its winter blanket of leaves

The flowers open as the temperatures warm, advertising their presence to early flying pollinators.  The veins in the pure white petals, contrasted with the yellow stamens surrounding the pistil in the center of the flower make a perfect target for foraging pollinators.  The stamens are the male reproductive parts, the pistils are the female reproductive parts.

Bloodroot (Sanguinaria canadensis)

The most likely flower visitors are early flying bees or flies that can tolerate low temperatures.

Bloodroot (Sanguinaria canadensis) with Bee

Each plant species evolves to utilize its energy to maximize the chances of survival and reproduction.  Like Hepatica and some other early spring flowers, Bloodroot’s strategy is to produce an enticing floral display whose only reward is pollen;  the flowers don’t produce nectar.  This works, because pollen is an important food source for many of the insects active at this time of year.  Bees consume pollen, and female bees also collect it to feed their larvae.  Flies and beetles visit flowers for their nutritious pollen.  Not many of the insects that prefer nectar, like butterflies, are active at the time Bloodroot is blooming, so there would be little added benefit in offering it.

As unpredictable as spring weather is, even the hardiest insects may not always be available in the short window of time a Bloodroot flower is open for business.  Each flower remains open for about three days, closing at night and on rainy days to protect its pollen when insects are unlikely to be active.

When a Bloodroot flower opens, its stigma, located at the tip of the pistil, is receptive.  Pollen must be deposited on the stigma in order for pollination to occur. At this time, the stamens are curved away from the stigma to clear the way for an insect’s access to the receptive stigma, hopefully bringing pollen.

Newly open Bloodroot (Sanguinaria canadensis) flower, in the female phase

After a few hours, some of the anthers, located at the tips of the stamens, begin to dehisce, or open, making pollen available.  The remaining anthers open gradually over the three-day period that Bloodroot flowers are typically open. The continuing separation of the anthers from the stigma helps minimize the likelihood of self-pollination.

Bloodroot (Sanguinaria canadensis) flower with some of the anthers open to make pollen available

Bloodroot (Sanguinaria canadensis) flower. Notice the pollen around the edges of the anthers where they have opened to make pollen available.

If after three days the flower has not been pollinated with the assistance of an insect, the stamens will begin to curve inward toward the center of the flower. The anthers touch the stigma, depositing the pollen.  In Bloodroot’s world, it’s better to self-pollinate to ensure reproduction than not to reproduce at all.  The flower drops its petals within hours of pollination.

Bloodroot (Sanguinaria canadensis) flower with some of the anthers beginning to curve back towards the stigma to enable self-pollination

After pollination, the thick, almost succulent leaves that protected the flower stem gradually open, expand, and capture energy from the sun for several more weeks.

Bloodroot (Sanguinaria canadensis) leaf in late spring. the leaf will continue to photosynthesize for much of the summer.

Pollinated flowers produce a fruit capsule that develops under the protection of the expanding leaves.  The capsule splits open when it’s ripe, making the seeds inside available for dispersal.  Like many early spring blooming wildflowers, Bloodroot has evolved to partner with animals, in this case ants, to disperse its seeds.  Each seed has  a packet of food called an elaiosome attached.  The elaiosome’s chemical make-up mimics the nutrition of insects, a preferred food for ants.  The ants take the seeds to their homes, where they eat the elaiosome and discard the seed, effectively planting it.

Both the common name, Bloodroot, and the genus, Sanguinaria, refer to the color of the sap found in the plants’ foliage and rhizomes (the plants’ underground parts).  This sap contains chemicals with a narcotic effect that Bloodroot produces to protect itself from herbivores. This is a common and highly effective strategy of the Poppy (Paperaceae) family, of which Bloodroot is a member.  As a result, Bloodroot does well even where there is serious deer pressure.

Native Americans have used Bloodroot for many medicinal purposes.  One of the chemical constituents of Bloodroot, sanguinarine, has also been used commercially in toothpaste and mouthwash to help prevent gingivitis. The red sap is also used as a dye.

Bloodroot can be found in rich, deciduous woods throughout much of the eastern two-thirds of the United States and Canada.  Look for it and other spring wildflowers along a wooded trail near you!

Bloodroot (Sanguinaria canadensis)

Related Posts

Hepatica’s Survival Strategy

A Carpet of Spring Beauty, Woven by… Ants!

A Tale of Two Spring Beauties

Dutchman’s Breeches and Squirrel Corn

Resources

Eastman, John.  The Book of Forest and Thicket.  1992.

Gracie, Carol.  Spring Wildflowers of the Northeast. 2012.

Hoffmann, David.  Medical Herbalism.  2003.

Illinois Wildflowers

Lady Bird Johnson Wildflower Center

Native American Ethnobotany Database

 

 

 

A Winter Show-off

My first encounter with Round-headed Bush Clover (Lespedeza capitata) was in late fall when the warm brown seed heads caught my eye.

Round-headed Bush Clover (Lespedeza capitata)

Throughout fall through winter, this plant is at its most dramatic, easily compelling attention away from nearby vegetation.

Round-headed Bush Clover (Lespedeza capitata)

When in bloom, Round-headed Bush Clover’s appearance is much more subtle, blending in with the grasses, Mountain Mints, asters, goldenrods and other plants that may share its territory.

Round-headed Bush Clover (Lespedeza capitata)

Round-headed Bush Clover has dense clusters, or heads, of small white flowers.  ‘Capitata’ in the scientific name means ‘growing in a dense head’, reflecting this arrangement.  The upper petal of each flower has a bit of an art deco vibe – they’re smudged with pink at the throat with ray-like veins radiating above.  This display may look delicately pretty to us, but to the many bees that visit the flowers it’s a beacon advertising food availability.

Round-headed Bush Clover (Lespedeza capitata)

The flower petals are protected by hairy sepals, green when the flowers are in bloom, then turning deep brown for fall and winter.  It’s these brown sepals that provide the eye-catching winter display.   If Round-headed Bush Clover’s strategy for enticing pollinators to visit is successful, dry (not fleshy) fruits will be tucked inside the dried sepals.

Hairs on plants are often an adaptation to protect the plant from being eaten, or too discourage free-loaders from stealing nectar when the flowers are blooming.  For example, ants visit flowers for nectar but rarely help with pollination because they are not a good anatomical match for the flowers’ reproductive structures, nor do the ants have the type of surface to which pollen might adhere.  The hairy sepals surrounding the flowers are likely to discourage ants from foraging the flowers, preserving the nectar for more effective flower visitors.

Round-headed Bush Clover (Lespedeza capitata)

Round-headed Bush Clover has three-part compound leaves, an arrangement that is common with clovers. It grows to a height of two to five feet (.6 – 1.5 meters).  Although the plant is somewhat shrubby-looking, it is herbaceous, that is, its above ground parts die back in the winter, and new shoots emerge from its roots for the next growing season.

In addition to offering food for pollinators, Round-headed Bush Clover is a food plant for the caterpillars of several butterflies, including the Silver-spotted Skipper,

Silver-spotted Skipper ovipositing (laying an egg) on Pokeweed (Phytolacca americana). Silver-spotted Skippers have the unusual habit of laying their eggs on plants near their caterpillar food plants.

Eastern-tailed Blue,

Eastern-tailed Blue on Butterflyweed (Asclepias tuberosa)

Gray Hairstreak,

Gray Hairstreak on White Clover (Trifolium repens)

Southern Cloudywing, Northern Cloudywing, Confused Cloudywing, Hoary Edge, and the Io Moth.

Dark-eyed Juncos, Mourning Doves, Bobwhites and Wild Turkeys are among the birds that may eat the seeds when they are available.

Dark-eyed Junco

Round-headed Bush Clover is native in most of the eastern two-thirds of the United States, and in Ontario and New Brunswick in Canada.  Searching for it in a meadow near you gives you a reason to go out for a winter walk!

Round-headed Bush Clover (Lespedeza capitata)

Resources

Beadle, David; Leckie, Seabrooke. Peterson Field Guide to Moths of Northeastern North America. 2012.

Cech, Rick; Tudor, Guy.  Butterflies of the East Coast.  2005.

Rhoads, Ann Fowler; Block, Timothy A.  The Plants of Pennsylvania.  2007

Stearn, William T. Stearn’s Dictionary of Plant Names.  1996

Illinois Wildflowers

Natural History Museum Hosts Database

USDA NRCS Plants Database

 

 

White Snakeroot, and a Bit of a Paradox

White Snakeroot (Ageratina altissima) provides food for late summer and fall visitors, primarily small critters.  Its button-like clusters of tiny tubular flowers offer nectar to a variety of potential pollinators, and flower buds and leaves provide food for other insect diners.

White Snakeroot (Ageratina altissima)

In my shade garden in central New Jersey, Bumble Bees and Small Carpenter Bees (Ceratina species) drink happily from the flowers.

White Snakeroot (Ageratina altissima) with Small Carpenter Bee (Ceratina species)

On a late September Sunday at Garden in the Woods in Framingham, Massachusetts, I watched while Bumble Bees and Honey Bees took advantage of White Snakeroot’s abundant nectar.

White Snakeroot (Ageratina altissima) with Bumble Bee (Bombus species)

White Snakeroot (Ageratina altissima) with Honey Bee (Apis mellifera)

In a sunny woods-edge location at Bowman’s Hill Wildflower Preserve near New Hope, Pennsylvania, several butterfly species found needed nourishment in the nectar  White Snakeroot flowers offered.

Painted Ladies and Sachem helped themselves to White Snakeroot’s sustaining beverage. These butterflies have been around much of the summer and fall, drinking from the flowers in bloom, moving from one species to the next as the season changed.

Painted Lady butterfly drinking nectar from White Snakeroot (Ageratina altissima)

Sachem drinking nectar from White Snakeroot (Ageratina altissima)

I was excited to see a Fiery Skipper, a butterfly that is rare in Pennsylvania, but a common resident in the southern United States. Fiery Skippers are among the butterfly species that regularly attempt to push the envelope of their range by emigrating to the north. White Snakeroot’s refreshing nectar rewarded this individual for its exploration efforts.

Fiery Skipper drinking nectar from White Snakeroot (Ageratina altissima)

Meanwhile, a Monarch fueled up for a flight in the opposite direction, heading south towards its winter territory in Mexico.

Monarch drinking nectar from White Snakeroot (Ageratina altissima)

If these potential pollinators do the job for which White Snakeroot has enticed them to visit its flowers, pollination occurs, and a type of fruit, called an achene, develops. The achene looks like a seed with a tiny hair-like parasol attached, designed to be dispersed by the wind to a favorable place for another White Snakeroot plant to germinate and grow.

White Snakeroot (Ageratina altissima), ready to disperse its fruit

At Bowman’s Hill Wildflower Preserve, an insect that looked a bit like a stink bug turned out to be the opposite – Harmostes fraterulus, one of the scentless plant bugs. Pennsylvania is thought to be the northern edge of Harmostes fraterulus’s range. Scentless plant bugs are a group of true bugs that lack glands to produce an unpleasant smell, quite unlike stink bugs who are named for their ability to do this. Harmostes fraterulus feeds on the flowers of several Aster (Asteraceae) family members, of which White Snakeroot is one.

Harmostes fraterulus on White Snakeroot (Ageratina altissima)

It’s interesting that this small insect is able to eat parts of White Snakeroot, since this plant contains potent toxins evolved to prevent herbivores from consuming it. These toxins are so effective that they can be fatal to mammals.  As you might guess, deer do not eat this plant.  If cows graze on a sufficient amount of White Snakeroot, the milk they produce is toxic to humans.  In the nineteenth century, many people became sick or even died as a result of drinking this tainted milk, most famously, Abraham Lincoln’s mother.

While this plant’s chemical defenses are potent enough to sicken or even kill large mammals, some tiny insects have successfully adapted to use this plant as their food source (host plant). A type of small fly species, a midge named Schizomyia eupatoriflorae, specializes on White Snakeroot buds.  The larvae of this midge live inside the plant tissue, prompting the plant to produce a rounded gall that the developing midge uses for both food and shelter until it is ready to emerge as an adult.

White Snakeroot (Ageratina altissima) with galls caused by the plant’s reaction to being used by a midge, Schizomyia eupatoriflorae

Flowers often have a lower concentration of a plant’s chemical defenses than do the other plant parts such as leaves and stems. But there are even insects who have evolved to specialize on White Snakeroot’s leaves.  The one of which I most often see evidence is a leaf miner, Liriomyza eupatoriella, a type of fly. The larvae of Liriomyza eupatoriella develop between the outer layers of the leaf, feeding on the tissues inside.

White Snakeroot (Ageratina altissima) with leaf mines caused by a leaf mining fly, Liriomyza eupatoriella

Mammals have plenty of other food alternatives (at least for now) without having to evolve a tolerance for White Snakeroot’s toxins. But tiny insects may gain an advantage if they can specialize on food that few others can consume (and live to tell the tale!), especially a relatively common food source like White Snakeroot.

Despite its toxicity, several Native American tribes found medicinal uses for White Snakeroot, often using the root, but other plant parts as well. Some sources say that a poultice to treat snakebites was made from the root, resulting in the common name, White Snakeroot.

White Snakeroot is a plant of woods and woods edges. It prefers light shade but can tolerate partial sun, with moist to slightly dry soils.  In Canada it is native in Ontario and Quebec provinces and the Northwest Territories, and in the United States from Maine to eastern North Dakota, south to Texas and the Florida panhandle, although it is much less widespread in the southeastern U.S.

American Goldfinch, taking refuge on White Snakeroot (Ageratina altissima)

 

Resources

Brock, Jim P.; Kauffman, Ken. Kaufman Field Guide to Butterflies of North America.  2003.

Cech, Rick; Tudor, Guy. Butterflies of the East Coast.  2005.

Coffey, Timothy. The History and Folklore of North American Wildflowers.  1993.

Eaton, Eric R.; Kauffman, Ken. Kaufman Field Guide to Insects of North America.  2007.

Eiseman, Charley; Charney, Noah. Tracks & Sign of Insects and Other Invertebrates. 2010.

Foster, Steven; Duke, James A. A Field Guide to Medicinal Plants and Herbs of Eastern and Central North America.  2000.

Rhoads, Ann Fowler; Block, Timothy A. The Plants of Pennsylvania.  2007

Illinois Wildflowers

USDA NRCS Plant Database

Harmostes fraterulus:

Maryland Biodiversity Project

Wheeler, A. G. Jr.; Miller, Gary L. Harmostes Fraterculus (HEMIPTERA: RHOPALIDAE): Field History, Laboratory Rearing, and Descriptions of Immature Stages. 1983.

Wheeler, A. G. Jr.  Harmostes reflexulus (Say) (Hemiptera: Rhopalidae): New Western U.S. Host Records, Analysis of Host-Plant Range, and Notes on Seasonality.  2013.

 

 

 

 

Partridge Pea Puzzles

Bright yellow Partridge Pea (Chamaecrista fasciculata) flowers peek out from between the stems of taller grasses and flowering forbs in meadows, prairies, stream banks and other open areas from July through early September.

Partridge Pea (Chamaecrista fasciculata)

Partridge Pea’s flowers are tucked in the leaf axils down the length of the stem.

Partridge Pea (Chamaecrista fasciculata)

Each flower has five yellow petals, with one much longer than the other four, and another partially curled toward the center of the flower, where its reproductive parts are located. A 1992 study showed that the curved petal directs floral visitors to the flower’s reproductive parts, first to the pistil (female reproductive part), and then the stamens (male reproductive parts).[1]  The red smudges on the petals are part of the visual allure to pollinators.

Partridge Pea (Chamaecrista fasciculata)

In the Partridge Pea flower in the photo above you can see the three evenly sized petals at the top, one petal in the lower left that curls toward the center of the flower, and an over-sized petal at the lower right. The stamens are mostly clustered at the middle of the flower.  The pistil resembles a hook projecting from beneath the right-most stamen. It is visible at the top of the over-sized petal.  Imagine a pollinator coming in for a landing using the over-sized petal as a runway, guided by the curved petal, with the red smudges on the petals as beacons. The pollinator brushes first against the receptive stigma at the tip of the pistil, depositing pollen from the last flower visited, then moves on to harvest pollen from the stamens.

Bumble Bee harvesting pollen from Partridge Pea (Chamaecrista fasciculata) flower. Bumble Bees are adept at buzz pollination.

Partridge Pea flowers offer pollen as a reward to their visitors, but they don’t produce nectar. As a result, bees that collect pollen are the most likely visitors of the flowers.  But the bees have to have skills in order to harvest Partridge Pea’s pollen, since it requires special handling in order to access it.  The pollen is dispersed through a slit at the tip of the stamen’s anther.  Pollen can be shaken out of the anther as a result of buzz pollination, a technique in which a bee clings to the flower while vibrating its wing muscles without actually moving its wings.  ‘Milking’ the anther with a series of strokes is another method of successfully harvesting Partridge Pea’s pollen.[2]

Honey Bee harvesting pollen from Partridge Pea (Chamaecrista fasciculata) flower. Honey Bees can’t perform buzz pollination, so may be using the ‘milking’ technique.

Eastern Carpenter Bee harvesting pollen from Partridge Pea (Chamaecrista fasciculata) flower.

Butterflies aren’t interested in Partridge Pea flowers, since they don’t offer nectar. But several butterfly species use Partridge Pea as a food plant for their caterpillars, including the Sleepy Orange and Cloudless Sulphur.

Sleepy Orange drinking nectar from Winged Loosestrife (Lythrum alatum)

Cloudless Sulphur

Gray Hairstreak and caterpillar on Partridge Pea (Chamaecrista fasciculata). Can you see the tiny caterpillar clinging to a leaf in the lower left of the photo?

When I saw a Gray Hairstreak butterfly spending time walking around a Partridge Pea plant, it seemed possible that this was a female laying eggs. Gray Hairstreaks use some Pea family members as caterpillar food, including clovers and tick-trefoils, although I haven’t seen any confirmation that they would use Partridge Pea.

Gray Hairstreak on Partridge Pea (Chamaecrista fasciculata).

A closer look showed that the butterfly was visiting Partridge Pea for nectar after all, but it was nectar that is made available through extrafloral nectaries on the base of the stem of each leaf.  This was a great benefit for the butterfly, but not much help for the plant, since the butterfly offered no services in return.

Gray Hairstreak drinking nectar from an extrafloral nectary on Partridge Pea (Chamaecrista fasciculata)

When present, extrafloral nectaries are generally a plant’s adaptation to entice insects that are predators of herbivores to visit and protect the plant. Ants are especially important in this role, since caterpillars are a very desirable food for them.  Some wasps and lady beetles are also potential protectors of plants.  While they are interested in nectar for themselves, they are also on the hunt for insects to feed to their larvae.  The wasps and lady beetles may rid the plant of the caterpillars or other insects who would eat it.  Nectar is provided in exchange for this protection.

Partridge Pea’s extrafloral nectaries look like tiny open pots, glistening with nectar, an open invitation to thirsty insects cruising through, not all of whom will offer services to the plant.

The two round pot-like appendages near the base of the Partridge Pea (Chamaecrista fasciculata) leaf stems are the extrafloral nectaries. Notice the glistening drops of nectar oozing from them.

While I have seen ants working Partridge Pea extrafloral nectaries, I was surprised at the variety of insects I saw drinking from them at one location I visited. It makes me wonder whether the cost of providing this nectar is worth the protection gained from them.  In addition to the Gray Hairstreak, I watched while a Bumble Bee spent more time visiting the extrafloral nectaries than the flowers.

Bumble Bee drinking nectar from a Partridge Pea (Chamaecrista fasciculata) extrafloral nectary.

After visiting several extrafloral nectaries, the Bumble Bee moved on to a flower.

I saw several Paper Wasps visit the nectaries. Since these wasps hunt caterpillars to feed their larvae, they do have the potential to provide a service in exchange for a tasty drink.

Paper Wasp (Polistes species) drinking from an extrafloral nectary on Partridge Pea (Chamaecrista fasciculata)

Paper Wasp (Polistes species) drinking from an extrafloral nectary on Partridge Pea (Chamaecrista fasciculata)

‘That was tasty!’ Paper Wasp (Polistes species) on Partridge Pea (Chamaecrista fasciculata)

Some accounts of Partridge Pea say that the leaves will sometimes fold up when they are touched. I’ve tried it several times, but I have never had Partridge Pea respond to my touch.  However, I have seen Partridge Pea plants with their leaves folded, so I’m guessing the plant folds its leaves in response to some stimuli, but I haven’t found an explanation for what it might be.  Maybe it’s a mechanism to prevent excessive water loss on hot, dry, or windy days.  Or maybe the plant responds to the touch of a butterfly laying eggs, and wants to minimize the leaf surface available to her.  I wish I knew!

Partridge Pea (Chamaecrista fasciculata) with leaflets folded. What prompted this?

If the name didn’t give away its family heritage, the fruits identify Partridge Pea as a member of the Pea or Bean (Fabaceae) family.  These fruits are an important winter source of food for birds, especially Bobwhites and Greater Prairie Chicken.

Partridge Pea (Chamaecrista fasciculata) with fruits typical of the Pea (Fabaceae) family.

Partridge Pea is an annual, but reseeds itself readily.  It likes sun, and can tolerate poor, dry soils.  It helps to fertilize soils through its release of nitrogen, and is sometimes used in stream bank stabilization.  Partridge Pea is native from Rhode Island to Minnesota in the north, south as far as southeastern New Mexico, and from Texas to Florida.

Partridge Pea (Chamaecrista fasciculate)

Related Posts

Will Work for Food – Extrafloral Nectaries

Cloudless Sulphurs Are on the Move

Sleepy Orange Butterflies are Back

Resources

Cech, Rick; Tudor, Guy. Butterflies of the East Coast.  2005.

Eaton, Eric R.; Kauffman, Ken. Kaufman Field Guide to Insects of North America.  2007.

Rhoads, Ann Fowler; Block, Timothy A. The Plants of Pennsylvania.  2007

Illinois Wildflowers

USDA NRCS Plant Database

USDA NRCS Plant Guide – Partridge Pea

[1], [2] Pollination and the Function of Floral Parts in Chamaecrista fasiculata, Andrea D. Wolfe and James R. Estes, 1992.

Natural Selection on Extrafloral Nectar Production in Chamaecrista Fasciculata: The Costs and Benefits of a Mutualism Trait

 

A Small Beauty: Purple Milkwort

As we walked the path between the woods and the meadow at the Pole Farm section of Mercer Meadows, Wood Nymphs flitted in and out of the foliage, Monarchs flew by, some mating, and a Clouded Sulphur dipped into the path to lay eggs, the tip of her abdomen touching the leaves of White Clover for a split second each.

Monarch butterflies mating

Wood Nymph

Glancing down, I saw a small group of plants that at first glance looked like a type of clover.

Purple Milkwort (Polygala sanguinea).

But it wasn’t clover. The plants had narrow, alternate leaves, and the tiny flowers were tightly packed into a somewhat flat-topped cylindrical cluster.  It was Purple Milkwort (Polygala sanguinea).

In profile, the outside of the flowers in the cluster (inflorescence) look like overlapping scales, similar to those on a pine cone. These scale-like structures are sepals, the outermost appendage of a flower.  When present, sepals protect the other flower parts as they mature.  In Purple Milkwort, two sepals fuse to form these scale-like outer flower parts, each for a separate flower.

Purple Milkwort (Polygala sanguinea), with unknown insect, probably a beetle, investigating its flowers

Viewed from the top, the inflorescence looks like a single very showy flower.

Purple Milkwort (Polygala sanguinea)

A closer inspection tells a different story. The outermost layers of the display look like white petals dipped in purple, but they are the sepals visible when the flower cluster is viewed in profile.  Moving inward, there are tube-like structures, in luscious shades of yellow, peach and a deep bright pink, reminiscent of popsicle colors.  These tubes are the fused petals of the individual flowers that form this cohesive cluster. At the very center of the inflorescence is a bouquet of buds that have not yet opened.  Together these flowers and buds offer an impressive show.

Purple Milkwort (Polygala sanguinea). The fused petals form a tube, initially yellow, then fading to peach and deep pink.

What explains the different colors of the floral tubes? If you look carefully, the yellow flowers are closest to the center of the display.  They are the most recently in bloom, open for business, the bright yellow actively beckoning pollinators.  The peach flowers have been open longer, and are shutting down.  The deep pink flowers have been in bloom the longest, and are no longer seeking pollinators for themselves.   This kind of color change is usually a plant adaptation to direct pollinators only to the receptive flowers that have not yet been pollinated.  It makes the most efficient use of the pollinator’s efforts from the perspective of both the pollinator and the plant.  While the peach and pink flowers are not beckoning pollinators for themselves, they continue to add to the attractiveness of the overall floral display.

This brightly colored display works! It attracts small to medium sized bees and bee-flies with tongues long enough to reach down the floral tube for a nectar reward.  The photos below show a Sweat Bee (Halictid bee, Augochlorini tribe) exploring the flowers.

Sweat Bee (Halictid bee, Augochlorini tribe) exploring a Purple Milkwort (Polygala sanguinea) inflorescence

Sweat Bee (Halictid bee, Augochlorini tribe) positioning its proboscis for a drink from a Purple Milkwort (Polygala sanguinea) flower

Mmmm, delicious! Sweat Bee (Halictid bee, Augochlorini tribe) drinking nectar from a Purple Milkwort (Polygala sanguinea) flower

Purple Milkwort can be found in the ground cover layer of meadows, prairies, open fields and woods edges from Nova Scotia west to Ontario in Canada, and in much of the eastern two-thirds of the United States, except Florida. It can grow to a height of four to sixteen inches (1-4 dm).  Both the common and scientific names reflect the color of the flowers and the milky sap the plant contains.  The genus, Polygala, is derived from Greek words that mean ‘many or much’ and ‘milk’, referring to the sap.  The species, sanguinea, is derived from a word that means ‘blood’.  Other common names for Purple Milkwort are Blood or Field Milkwort, reflecting its color or habitat.  Although common, it’s not always easy to spot this little beauty.

Follow the camera lens to the Purple Milkwort in the shadows in the lower left of the photo.

Resources

Mauseth, James D. Botany An Introduction to Plant Biology.  2014.

Rhoads, Ann Fowler; Block, Timothy A. The Plants of Pennsylvania.  2007

Stearn, William T. Stearn’s Dictionary of Plant Names.  1996

Wilson, Joseph S.; Carril, Olivia Messinger. The Bees in Your Backyard. 2016.

Flora of Wisconsin

Illinois Wildflowers

Minnesota Wildflowers

USDA NRCS Plants Database