Ranunculus acriformis var. aestivalis L. D. Benson.

Ranunculus acriformis var aestivalis, is commonly referred to as autumn buttercup since it flowers late in the season. It is a member of the Ranunculaceae family. This species is a finely pubescent, upright perennial herb. It grows to between 30 to 60 cm tall, and its twice ternately divided leaves are largely in a basal cluster. Autumn buttercup produces abundant yellow flowers that can be seen from late-July to early October. It is found in low, herbaceous, wet meadow communities on islands of drier peaty hummocks, and sometimes in open areas, at elevations ranging from 1940 to 1965 meters. The species' habitat has been much reduced from pre-settlement times by the diversion of water for irrigation and the introduction of domestic grazing animals. There are currently only two small populations of the autumn buttercup known to exist.

First collected in 1894 near Panguitch by Markus E. Jones, Utah, then rediscovered by L. Benson in 1948, this species is considered rare and is listed as federally endangered, with only two known sites in southern Utah, a saline meadow south of Panguitch in the Sevier River Valley and a riparian meadow in Boulger Canyon, Emery County. R. Van Buren et al. (1994) treated this variety as a distinct species, R. aestivalis by emphasizing the differences in saline habitats of the Sevier Valley population. However the DNA evidence he presented indicates that the three varieties of Ranunculus acriformis form a single clade with R. acriformis var. aestivalis as sister group to the other two ( Ranunculus acriformis var. acriformis and Ranunculus acriformis var. montanensis (Rydberg) L. D. Benson). Further only minor morphologic differences occur between these varieties, and hence I consider this a variety of Ranunculus acriformis.

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