What wonders the white overshadowed

Last time I left you and a question hanging: beneath the canopy of a colony of snow-on-the-prairie plants, Euphorbia marginata, what were more than a dozen little patches of purple? Today’s close-up of one of those patches reveals it to be a sort of purple pineapple. Here is a case of what botanists call convergent evolution: two unrelated species of plants come to resemble each other in some characteristic way. You are looking at a flower head of Eryngium leavenworthii, commonly called eryngo, but sometimes also known—and who could blame anyone for the name?—as false purple pineapple.* This purple “pineapple,” whose leaves and crown end in spines that can easily get into your skin, turns out to be a member of the family that includes the Eurasian food plants parsley, fennel, celery, dill, anise, cumin, caraway, coriander, and carrots. But the inedible eryngo is native to the Great Plains of North America, and one way that it distinguishes itself from the tropical pineapple, other than its color and much smaller size, is by the presence of protruding stamens, some of which you can see near the base of the core of the “pineapple” that is actually a flower.

For more about eryngo, including a clickable map showing where the species grows, you can visit the USDA website.

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* Update on September 15.  I’m beginning to think that the “sometimes also known” refers to me and me alone. I expect I conflated eryngo’s pineapple-y appearance with “false purple thistle,” a phrase that other people have indeed called eryngo because of its spines.

© 2011 Steven Schwartzman