Non-technical Description: Colorado butterfly plant is a short-lived perennial herb with 1-few reddish, pubescent stems 50-80 cm tall. Lower leaves are lance-shaped, with smooth or wavy-toothed margins and average 5-10 cm long, while those higher on the stem are smaller and reduced in number. The inflorescence is located above the leaves and is flat-topped when in bud. The multiple branches of the inflorescence elongate as the flowering season progresses. Usually only a few open flowers are present at any time and are located between the floral buds and the mature fruits. Flowers have 4 white petals (turning pink with age) and are 1-1.5 cm wide. The hard, nut-like fruits are 4-angled and sessile. Flowering occurs from late June to late September or early October (Fertig 2000).
Similar Species: Gaura parviflora is an annual with a narrow, elongate inflorescence and white flowers less than 3 mm long. G. coccinea is a low, bushy perennial with leaves less than 3 mm long. Rosettes of Cirsium flodmanii and Oenothera spp. are similar, but are more pubescent.
Habitat: Typically occurs on subirrigated soils on level or slightly sloping floodplains and drainage bottoms at elevations of 5000-6400 feet. Colonies are often found in low depressions or along bends in wide, meandering stream channels. Most populations are found a short distance from the actual channel and may even occur at the base of low, alluvial ridges at the interface between riparian meadows and drier grasslands. On wet sites, Colorado butterfly plant is often associated with communities of Agrostis stolonifera and Poa pratensis, while in drier habitats it may occur in stands of Glycyrrhiza lepidota, Cirsium flodmanii, Grindelia squarrosa, and Equisetum laevigatum. Salix exigua and Cirsium arvense may become locally dominant in habitats that are not periodically flooded or otherwise disturbed. Colorado butterfly plant occurs on soils derived from conglomerates, sandstones, and tuffaceous mudstones and siltstones of the Tertiary Wind River, Arikaree, and Ogalalla formations. Average annual precipitation within its range is 13-16 inches, with the majority falling as rain (Fertig 2000).
References: Fertig, W. 2000. Status review of the Colorado butterfly plant (Gaura neomexicana ssp. coloradensis). Report prepared for the Wyoming Cooperative Fish and Wildlife Research Unit, US Fish and Wildlife Service, and Wyoming Game and Fish Department by the Wyoming Natural Diversity Database, Laramie, WY.Floyd, S.K. and T.A. Ranker. 1998. Analysis of a transition matrix model for Gaura neomexicana ssp. coloradensis (Onagraceae) reveals spatial and temporal demographic variability. International Journal of Plant Science 159(5): 853-863
Author: Walter Fertig, Moenave Botanical Consulting, Kanab, UT. April 2017