Draba norvegica Gunn.
Norwegian Whitlow Grass
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Basis for Listing
Draba norvegica is a small plant of the far north with amphi-Atlantic distribution, that is, primarily in northeastern North America and northwestern Europe. In North America, it occurs occasionally on limestone barrens, gravelly shores, bedrock ledges, and cliffs in arctic and subarctic coastal regions of northeastern Canada. There are also a few remarkable populations that are disjunct in the interior of the continent, including one in Minnesota.
Draba norvegica is small perennial plant with leaves crowded near the base. It has an unbranched flowering stalk that rises up from 5 to over 10 cm (from 2 to over 4 in.) in height. It is superficially similar to several other members of the mustard family but can be distinguished by the following combination of characters. It is a perennial, the basal leaves are simple (undivided), and the hairs on the leaves are uneven in length and of different types - some hairs are simple, others bifurcate or stellate (star-shaped). The capsules (siliques) are glabrous or nearly so.
Draba norvegica is primarily a plant of arctic and subarctic habitats. It is found in Minnesota only on an island in Lake Superior that is composed of Precambrian rock. The island is offshore from the mainland by about 7-10 km (4-6 mi.). The interior of the island is forested with Picea spp. (spruce) and Abies spp. (fir) trees, and the margins consist of exposed bedrock. Draba norvegica occurs on the rocky shore about 5 m (16 ft.) above the lake level and with a south or southeast exposure. Plants are rooted in narrow crevices in the rock with just enough foothold for them to survive the harsh conditions on the rocky shoreline.
Biology / Life History
Draba norvegica is a perennial herb that appears to reproduce regularly by seed. Little is known about the life history of the Minnesota population, such as how often it produces new plants from seed or how many years an individual can survive.
Conservation / Management
Draba norvegica is at risk because the only population in Minnesota consists of a relatively few individuals concentrated in a very small area. This makes it vulnerable to a number of natural and human-caused mishaps that could inadvertently wipe out the population. Fortunately the site is inaccessible and rarely visited by people, so human threats are minimal.
Conservation Efforts in Minnesota
The DNR's Minnesota Biological Survey is in progress in northeastern Minnesota. Botanists agree that potential habitat for this species has been well-searched, and that substantial new populations are unlikely to be found in Minnesota. Based on available information, land managers have a sound basis for implementing protection strategies for the single known population.
Butters, F. K., and E. C. Abbe. 1953. A floristic study of Cook County, northeastern Minnesota. Rhodora 55:21-201.