Symphyotrichum ericoides var. pansum
formerly Aster pansus
Tufted white prairie aster is also known as manyflowered aster. It is a fibrous-rooted perennial with clustered stems rising from 30-200 cm high. The herbage is rough with spreading to appressed hairs. The numerous leaves are firm, mostly linear in shape and usually less than 7 cm long and 5 mm wide. See the photo of the upper leaf surface below.
The numerous flower heads are small, with the disk only 4-8 mm wide. The 15-30 rays are white, with each measuring from 3-8 mm long. The involucre measures 4-7 mm high with the bracts ranked, the outer firm with rounded to squared tips.
Tufted white prairie aster may be found in open, wet to dry places in the valleys and plains. It is often found along the drying margins of streams and ponds. It is tolerant of alkaline conditions.
Aster pansus is found from southern British Columbia and central and eastern Washington east to Montana and hence south to Utah, Colorado and Nebraska.
In the Columbia River gorge, it may be found at an elevation of 200' at a vernal pond west of Horsethief Lake State Park.