The Rarest Plant in WyoBraska: The Colorado Butterfly Plant

Travel and Explore WyoBraska


In a pocket-sized section of WyoBraska, where an invisible line in the rolling prairie joins Wyoming, Colorado, and Nebraska, grows one of North America’s most endangered plant species.

If you’ve ever hiked through the high plains meadows or along the wandering streams of WyoBraska, you may have been lucky enough to catch sight of the Colorado Butterfly Plant (Oenothera coloradensis), a short-lived perennial herb in the evening primrose family.

Colorado Butterfly Plants were first collected near Fort Collins, Colorado in 1894, which explains the “Colorado” part of its name. The “Butterfly” is derived from the bilaterally symmetrical — meaning that the two pairs of petals are mirror images of each other — petals, which resemble the wings of a butterfly.  In its first year of life, it is a simple cluster of leaves. In its second year, the plant produces one to several reddish stems 50-80 cm tall (19-31 inches) and begins to flower. 

The Colorado Butterfly Plant. © Julie Reeves / USFWS
The Colorado Butterfly Plant. © Julie Reeves / USFWS

From June through September, the pinkish-white flowers open in the late afternoon, bloom throughout the darkness of night, where they are pollinated by noctuid moths (an insect family which includes the widely despised, but vital to our ecosystem, Miller moth), and then close at dawn. The plants, beginning in July, each produce between 140 and 175 hard, nut-like fruits, which contain 1-4 seeds per fruit. Seed dispersal is believed to be dependent on flood waters moving the seeds to new locations.

Today, due to its very small range, and exceptionally specific habitat needs, which consist of sub-irrigated, alluvial soils of drainage bottoms surrounded by mixed grass prairie (or in simpler terms: the wetland area between the creek and the prairie), Colorado Butterfly Plant is found only in a 1700 acre area in southeastern Wyoming, western Nebraska, and northeastern Colorado, between the elevations of 5000 to 6400 feet. In Nebraska, where the plant is listed as endangered, it is found only in a small section of Kimball County near Oliver Reservoir, and along the floodplains of Lodgepole Creek.

The Colorado Butterfly Plant. © Nebraska Game and Parks
The Colorado Butterfly Plant. © Nebraska Game and Parks

For plant species, Endangered Species Act protection is only applicable on federal land and does not apply to private land. The only federal land in Wyoming where Colorado Butterfly Plant is found is F. E. Warren Air Force Base near Cheyenne, and so the base has become a center for research and protection. Although F. E. Warren is relatively small as far as military installations go (630 acres), it contains three sites suitable for the finicky nature of the Colorado Butterfly Plant and supports a large population of between 6000 and 8000 plants.

The Air Force has been taking steps since 1984 to monitor and protect this delicate species. Every year, field botanists walk through the riparian zones of the base, and count every Colorado Butterfly Plant that they can find. It’s hot, difficult, and often thankless work, but vital to the conservation of this rare flower.

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In the wild, however, only fourteen known sites exist where Colorado Butterfly Plant is still growing, and within these small populations, only an estimated 3000 plants are left.

Without better land management practices, including the limit of broadleaf herbicide use, haying in late summer in order to give the flowers a chance to produce seeds, shorter-term livestock grazing, and control of urban expansion, it is unlikely that Colorado Butterfly Plant will survive much longer in Nebraska, where the plant is still listed as endangered, despite being removed from the Federal List of Endangered and Threatened Plants in 2019. Control of invasive plant species such as Canada thistle is also critical, as Colorado Butterfly Plant is unable to compete for survival against many of these invaders.


There are not enough photographs of this amazing plant to create a photo gallery of images despite our photographers attempting to find, and document, the plant for three days. Most of the remaining plants are living on private, inaccessible, and protected lands in southwestern Nebraska, southeastern Wyoming, and central northern Colorado (the WyoBraska region). We’re still looking.

Oliver Reservoir Kimball, Nebraska. © Hawk Buckman
Oliver Reservoir Kimball, Nebraska. © Hawk Buckman

If you are fortunate enough during your travels through Nebraska to spot one of these nearly extinct flowers, be sure to take photos, note the location (use the GPS on your phone), and contact Nebraska Game and Parks at 402-471-0641.

Story by: Kathrine Rupe
Photography by: Sarah Yakawonis
Photography by: Julie Reeves / USFWS

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