Plant Story--Native Wildflower, Gumweed, Grindelia

Gumweeds, genus Grindelia (sunflower family, Asteraceae) are roadside wildflowers, most common in western North America but with a few species in the East and South. A gumweed is easy to recognize: note the funny spines around the flower buds (especially visible in the picture below). In addition, gumweeds are gummy--if you touch the buds or flowers, sticky stuff comes off on your fingers.

But there is a lot more to gumweeds.

People across the Americas used gumweeds medicinally. When German Commisson E studied extracts of Grindelia to see if they worked by scientific standards, they concluded yes, and approved Grindelia extracts as safe and effective medicine for problems of the upper respiratory tract link. The species German Commission E studied, Great Valley gumweed, Grindelia camporum of California, is not found east of Nevada, but Native American tribes across the range of the genus Grindelia used the plants similarly, as do South Americans, indicating shared chemistry effective for upper respiratory complaints. (North American ethnobotany of Grindelia: link)

Although it looks spiny in my photo, it is not. Very sticky, however.

Gumweed contains many active compounds including diterpene acids, volatile oils, polyynes, saponins, terpenes and flavonoids. In laboratory experiments, gumweed extract killed bacteria and fungi. The Shoshoni and Northern Cheyenne used it as a disinfectant and many tribes treated skin problems with it. Today herbal medicine sources list a decoction of curlycup gumweed as a treatment for poison ivy, which was one of the applications of Great Valley gumweed that caught the attention of Europeans in California in the 1800s.

The young leaves were also made into tea, which, if it is effective for upper respiratory complaints, would be a good tonic. Curlycup gumweed is, however, a facultative selenium absorber, which means that it doesn't necessarily contain selenium but if there is selenium in the soil, it becomes concentrated in gumweed leaves and stems. Since selenium is essential, but toxic in large amounts, gumweed should not be consumed in large quantities over a long period of time, certainly not in areas where there is lots of selenium in the soil (about selenium link, map).

I'm always surprised when I find plants historically used as chewing gum. This was one. Native Americans used gumweeds as chewing gum. They simply chewed the sticky flower heads. I'll try it when I next see a plant in bud--soon--though I don't generally much like to chew gum.

There are many species of Grindelia, but Grindelia squarrosa, curly cup gumweed, sometimes called curlytop gumweed, rosinweed or resinweed, is the most widespread in North America, found from California to Massachusetts (USDA map: link).

Although it appears in weed books, curlycup gumweed isn't on any state's noxious weed list and I haven't seen it listed as a problem in crops or rangeland. It is a short-lived perennial of lightly disturbed sites. In nature, lightly disturbed areas were small fires or the edges of buffalo wallows and prairie dog towns. Studies have confirmed the presence of gumweeds in that sort of habitat. In fact, a study on the Colorado Front Range found curlycup gumweed grew so predictably in areas that had had a not-very-severe fire, that it could be used as an indicator of past fires.  Today lightly disturbed areas are rural roadsides and unpaved access roads.

Native birds such as the sage grouse consume a lot of curlycup gumweed seeds but cattle, sheep and horses won't generally graze the plants--too gummy.

Curlycup gumweed is one of a rather small group of plants that produce two quite different types of seeds. In gumweed's case, the outside little flowers, ray florets, and the central flowers, disc florets (about composite flowers link) have different conditions for germination. Under almost all the conditions tested, the seeds from disc florets germinated faster and survived better. On the other hand, being tough to germinate means the seedling doesn't commit to growing in a warm February, to be killed by the March snowstorm. Germination conditions vary greatly from year to year and site to site. The two types of seeds are interpreted as greatly extending the conditions under which gumweed successfully germinates and will protect it from dying out locally as it might if all its seeds germinated in the same year.

This is an attractive but easily overlooked widespread native wildflower. As the Forest Service summary reports "Curlycup gumweed is used as an ornamental. It produces flowers over a long period, even when the soil is poor and dry." (p. 5)

The scientific name Grindelia honors the Russian botanist D. H. Grindell (1777-1836), but I always thought of "grin" when I saw the plant, that is, a smiling flower. Grin, Delia. A likeable, adaptable native.


Comments and corrections welcome.

References
Keith, R. P., T. T. Veblen, T. L. Schoennagel adn R. L. Sherriff. 2010. Understory vegetation indicates historic fire regimes in ponderosa pine-dominated ecosystems in the Colorado Front Range. Journal of Vegetation Science. 21 (3): 488-499.
McDonough, W.T. 1975. Germination polymorphism in Grindelia squarrosa. Northwest Science. 49: 190-200.
Moerman, D. E. 1998. Grindelia squarrosa. Native American Ethnobotany. Timber Press, Portland OR. online 
PDR (Physician's Desk Reference) for Herbal Medicines. 2007. 4th ed. Thompson Publishing, Montvale, New Jersey.
US Forest Service. Grindelia squarrosa. link
Whitson, T. D. editor. 1992.Weeds of the West. University of Wyoming Press, Laramie, WY.

Kathy Keeler, A Wandering Botanist

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