Fred Harris points out rare plants in rock outcrop pools on Touch the Sky Prairie.

Ephemeral Rock Pools - touch the Sky Prairie, Rock County, Minnesota

Fred Harris, Botanist with the Minnesota County Biological Survey, has recently catalogued several rare species of plants on the Touch the Sky Prairie Unit (TTSP) of the Northern Tallgrass Prairie National Wildlife Refuge.  Staff from the Windom WMD, Big Stone NWR, Rock County Land Managment, Rock County NRCS and the Luverne High School toured the area observing plants that occur in temporary rainwater pools on rock outcrops. 

Many of these pools are present on the TTSP. Ephemeral rock outcrop pools vary from small, one foot diameter puddles in bedrock depressions to pools of 25 feet across.  All of these pools are at least eight to ten inches deep, last for one to two months and dry up by late June most years. 

Cosmogenic ageing indicates that the rocks on TTSP were covered by glaciers 400,000 to 600,000 years ago. 

Species observed on the tour include Black-footed Quillwort, Water Starwort and Wolf's Spikerush.  The population of quillwort on TTSP is the largest in Minnesota and occurs in rock outcrops in Rock and Pipestone Counties only.  Wolf's spikerush is a state endangered species and there are very few records of this plant - two records are from the Minnesota River valley and there are about six records in Rock County. 

Hairy waterclover, although not seen today, has been encountered in one spot on the unit.  Other species of note include fame flower, rock spikemoss, popcorn flower (this is the northern edge of its distribution) and mudwort, a species that occurs only on rock outcrops.