Illinois Natural History Survey - University of Illinois

Prairie Trout Lily

Susan Post

Location, location, location is everything in real estate. In botany, however, if not everything, it can often provide a definite clue to a plant’s identity—a  clue Charles Robertson should have considered when he was collecting in 1880. Erythronium mesochoreum, the prairie trout lily, looks like the white trout lily but grows in a different habitat. When it was first collected in Illinois on April 3, 1880 from Macoupin County near Carlinville, Robertson identified the specimen as the white trout lily (E. albidum), not taking into consideration the habitat where  the plant was growing. One hundred years would pass before E. mesochoreum  would be discovered again and Robertson’s specimens correctly identified by Illinois Natural History Survey (INHS) botanists.

During 1981, botanists from INHS, the Illinois State Museum, and the Illinois Department of Natural Resources observed and collected a trout lily on a prairie remnant in Macoupin County. They identified it as the prairie trout lily. Until this discovery, prairie trout lily was not recognized as occurring east of the Mississippi River. The closest occurring population was found in Pike and St. Louis counties of Missouri.

While the initial impression (both have singular white flowers with yellow stamens) may serve to confuse prairie trout lily with the woodland, white trout lily, there are several distinguishing characteristics. The prairie trout lily is a plant of the dry, southern tallgrass prairies and open oak woodland habitats. It occurs in southern Iowa, eastern Nebraska, eastern Kansas, Missouri, Oklahoma, and north-central Texas. It has an earlier blooming period—March through early April—in Illinois. The leaves are narrow, folded along their length, and usually lack speckling.  In the white trout lily, the speckling of the leaves led to the common name trout lily, referring to their resemblance to the markings on a trout. The prairie trout lilly’s fruit droops to the ground at maturity, whereas, in the white trout lily the fruit is held erect.  The white trout lily produces runners that are usually covered by leaf litter, whereas, the runners are absent in the prairie trout lily.  A final distinguishing character is that immature, single-leaved plants are infrequently found when the population is in flower.  This is in marked contrast to the white trout lily, which can carpet the understory of woods with its leaves, while only a few blooms make their appearance.

The white trout lily is known from moist woods throughout Illinois.  Prairie trout lily is known mainly from a few western locations in Illinois. Denby Prairie Nature Preserve in Macoupin County is one of the few sites where this plant may be observed.

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