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.

 

 

 

 

10 thoughts on “White Snakeroot, and a Bit of a Paradox

    • I don’t have a lot of information about that, but I think not. Plants often produce different chemicals in their nectar and pollen than they do in their leaves and stems. This is because of their love-hate relationship with animals. They’re trying to attract animals (often insects) to visit their flowers, to help the plants with pollination, so they don’t want to poison flower visitors. On the other hand, they do want to discourage animals from eating the plants, which could kill the plant, or at least significantly reduce its vigor. Here’s a source that lists White Snakeroot as a good source of food for honey bees: http://www.pollenlibrary.com/Specie/Ageratina+altissima/

      • I understand that honey made from Pieris nectar, if concentrated enough, can kill a person, but does not disturb the bees. I’m guessing it would depend on concentration. I did get a splatter of moisture on my face when pruning under a pieris – I absentmindedly licked my lips, noticed it was very sweet, realized it was pieris nectar, and had a friend research my danger level. She said it would take about a full teaspoon or more to cause ill effects and I didn’t notice any problems from the small amount that hit my lips. Which is a long way of saying what doesn’t hurt a honeybee may hurt you and me. I don’t know where one would look to discover how much nectar from snakeroot would lead to problems in humans.

  1. Very informative with such beautiful photos. This makes such an excellent record of your local wildlife. I’m a long way away in Southern Spain and sometimes the U.K. But this brings me close to other nature aficionados! Just reading a book that ends up being set in Pennsylvania about botany, botanists and business in the 18 to 19th century. The Signature of All Things.

    • I’m glad you enjoyed the post. It’s great that we can all share our love of nature this way. I’ll have to read ‘the Signature of All Things’. I believe the author lives just a bit north of me in New Jersey, or did at one time.

Comment

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s