slender phlox

Microsteris gracilis is an annual herb which is variable in shape, taking a decumbent, branching, sometimes almost tuftlike form or growing erect and very slender. Its maximum height approaches 20 centimeters, but it may be much smaller. The lance-shaped leaves are 1 to 3 centimeters long and oppositely arranged except for the upper ones, which are alternate. The herbage is glandular and hairy in texture. The inflorescence at the top of the stem bears one or more small flowers. The flower has a tubular throat around a centimeter long encased in a tubular calyx of sepals. The flat corolla has five flat-tipped or notched lobes just 1 or 2 millimeters long. The flower is white to bright pink with a yellowish throat.

Microsteris gracilis is native to western North America from northwestern Canada to the American Midwest and West Coast, through Mexico, as well as South America from Peru to southern Chile. In Canada it does sometimes occur in the Yukon, but its has not established a recurring population. It is stated to be introduced to the Yukon in the Flora of Alberta, but is listed as native in Plants of the World Online. In British Columbia and Alberta it is found in southern parts of the provinces. In the northwestern United States it is common throughout Washington and Oregon, mostly found in southern Idaho, and widely scattered in Montana. Southward in Wyoming it is recorded in all but four counties and is found on both the western and eastern slopes of Colorado. It reaches its easternmost native distribution in a few western counties of South Dakota and Nebraska. In the southwestern US the species is native to all the diverse plant communities in California, with records in almost every county. It is likewise found in all but one county in Nevada and all but five counties in Utah. Plants grow in most of Arizona, but only in western counties of New Mexico. South of the border it is found in just two northwestern Mexican states, Baja California and Sonora.