Hoary Whitlow Grass
- Name also: Hoary Whitlowgrass, Twisted Whitlow-grass, Twisted Draba
- Family: Mustard Family – Brassicaceae (Cruciferae)
- Growing form: Biennial or perennial herb.
- Height: 10–30 cm (4–12 in.). Commonly many-branched or stem branching, sturdy, many-leaved, densely stellate-haired and straight-haired. Base sometimes also flowerless rosettes.
- Flower: Corolla regular (actinomorphic), white, approx. 0.5–1 cm (0.2–0.4 in.) wide; petals 4, notched, 3–5 mm (0.12–0.2 in.) long. Sepals 4. Stamens 6, of which 4 long and 2 short. Gynoecium fused, a single carpel. Inflorescence a raceme.
- Leaves: Dense basal rosette and alternate on stem, almost stalkless. Rosette leaves elliptic–lanceolate, narrow-based, with almost entire edges, grey, both sides stellate-haired, base commonly also with unbranched hairs, withering early. Stem leaves elliptic, wide-based, with toothed margins, hairy.
- Fruit: Many-seeded, elliptic–lanceolate, flat, glabrous–hairy, commonly alternate, 7–10 mm (0.28–0.4 in.) long silicula. Stalk 1–3 mm (0.04–0.12 in.), commonly glabrous, quite erect.
- Habitat: Shingly and rocky sea-shore meadows, dry sloping juniper forests. Lapland river-side meadows, beside railways and roads, yards.
- Flowering time: June–July(–August).
Generally speaking, identifying genus Draba plants is difficult: borders between the species can be very tight and differences in the amount of hair have been regarded as a good basis for classification. Hoary whitlow grass is not that difficult to identify, however, and is easy to pick out among its relatives and other Mustard family plants. It is characterized by many stem leave, which are densely packed on the stem and its grey colour which is caused by its hairiness. In the fruiting stage the somewhat flat, lanceolate, usually curling siliqulae that are typical of the plant and its relatives is a good way to be sure of what it is. Hoary whitlow grass is usually self-pollinating, so fruits develop irrespective of the amount of insect activity around the flowers. Sometimes the basal rosette on overwintering plants grows runner-like branches which live on after the flowering stem dies.
Hoary whitlow grass’s habitat in Finland is divided in two. It grows in the south-west quite commonly as a native beside the sea, beyond the reach of high waters on stony and shingly meadows. Around the Baltic Sea its habitat covers the Åland Islands and the rest of Finland’s south-western archipelago, along the coast of the Gulf of Finland to the Bay of Vyborg and on the shores of the Bothnian Sea to the Kvarken archipelago and the islands of Pietarsaari. Hoary whitlow grass also grows in Lapland as an alien species along river banks and close to people in meadows and fields closest to the house, and even on turf roofs. The southernmost of these stands are in Muonio, Kittilä and Sodankylä.
Most genus Draba plants thrive in cold conditions, including mountains. In Finland too, most of the dozens of representatives of genus Draba grow in Lapland and four grow only in the high fells of Finland’s north-western “arm”. In the south of the country its close relatives woodland draba (D. nemorosa) and wall whitlow grass (D. muralis) can also be found.