Desert Laxative

When I first moved to Arizona from New Orleans where I was finishing training at Tulane, I began to familiarize myself with the local weeds, trees, and grasses that were important causes of allergy problems in the Southwest.  Some plants were on every local allergist’s list of important allergenic plants, and although some of the names on the list – like Oak and Ragweed – were very common, the Arizona varieties looked very different from their southern cousins.  It took a while, but in time I became familiar with all of the plants on the list.  There were a few however, that had me stumped.

Most of the Arizona allergists I knew had English Plantain (Plantago lanceolata) on their list of important allergenic weeds and yet after years of hiking around,  I never saw anything that looked like the delicate pictures of this weed in the books.

In fact, English Plantain is prevalent around the eastern coastal states, the Northwest, and California where it an important allergen – but not in the deserts of Arizona. So why is it on the list?

The Elusive Plantain

After an unusually rainy winter this year, the desert bloomed as I have never seen it before. The usually brown hues of South Mountain were transformed into a carpet of green.  One morning when out riding my bike,  I noticed a vaguely familiar-looking weed growing on the rode side of the new Chandler extension in Ahwatukee.  I took a few pictures and collected samples to make a pollen reference. Sure enough, it seemed to be the elusive plantain.

This was not English Plantain but a close cousin Plantago ovata.  This variety of plantain is only found in the Southwestern United States and has a number of common names including Desert Indian Wheat. It has been used by the Pima Indians for food and medicine for millennia.

The seeds of Plantago ovata are a common source of psyllium which is used in the manufacture of bulk laxatives and has been a cause of occupational allergy and asthma in workers exposed to the plant.  

In Phoenix, the plant appears briefly during the spring, particularly after a wet winter, contributing to the display of desert wildflowers… and to the spring allergy season.