Spring Whitlow Grass
- Name also: Common Whitlowgrass, Vernal Whitlow-grass, Early Whitlow Grass, Spring Draba, Shadflower, Nailwort
- Latin synonym: Erophila verna
- Family: Mustard Family – Brassicaceae (Cruciferae)
- Growing form: Annual, overwintering herb.
- Height: 3–10 cm (1.2–4 in.), up to 15 cm (6 in.) in fruiting stage. Stem a leafless scape.
- Flower: Corolla regular (actinomorphic), white, approx. 0.5 cm (0.2 in.) wide; petals 4, tip deeply bifid, 2–4 mm (0.08–0.16 in.) long. Sepals 4, commonly reddish. Stamens 6, of which 4 long and 2 short. Gynoecium fused, a single carpel. Inflorescence a raceme, extending in fruiting stage.
- Leaves: In a basal rosette. Blade lanceolate–obovate, with narrow base, with quite tapered tip, margins entire or rarely toothed, top stellate-haired.
- Fruit: Many-seeded, quite elliptic, flat, glabrous, 4–7(–10) mm (0.16–0.28(–0.4 in.) long silicula. Stalk approx. 10 mm (0.4 in.).
- Habitat: Rocky outcrops, meadows, dry-stone walls, brick walls, railway embankments, yards, paths, sloping pastures.
- Flowering time: April–May.
Spring whitlow grass is a herald of spring: its older generic name means ‘fond of spring’ and the species name is ‘spring-like’. It begins to flower as soon as the snow melts at the end of April or beginning of May and grows on meadows with the thinnest of soils where water from the melting snow evaporates completely within a couple of weeks. The plant’s life-cycle is just as quick: the seeds are ripe at the end of May and the green parts have withered. Spring whitlow grass’s fast rhythm and short life means that it does not rely on fickle insects to fertilise it: it self-pollinates and perhaps for that reason the root is very long-lived. The form of the fruits, the hairiness of the leaves, the size of the flowers and even the number of chromosomes can all vary between individuals or populations. Spring whitlow grass was the first plant to be observed to determine the importance of self-pollination to mutation and the creation of local stands. Over 200 local stands were studied and classed as separate species. Spring whitlow grass can be more broadly divided into four species comprised of close relatives, but the differences between them are statistical, meaning that they are only apparent as deviations from averages between large groups. Placing a population or single plant in these species is difficult, so it is easier to regard spring whitlow grass as a diverse species-group.
Spring whitlow grass’s leaf rosette is no bigger than a large coin, and its inflorescence doesn’t reach higher than a hand-span. These small flowers add a little white colour to the otherwise bare ground, hover, as they grow in white bunches. There are usually hundreds in a single square metre, perhaps even thousands. Its flower buds open in the morning at the same time and likewise close together in the evening. This rhythm is born of the fact that the corolla cells grow while the plant is flowering. The corolla enlarges slightly as flowering continues. The species can be differentiated from its close relations by examining the corolla: petals of other whitlows have notched tips at most. Also, most genus Draba plants grow in Lapland while spring whitlow grass is common only in the southernmost quarter of the country and becomes quickly rarer further north. It has been spotted growing around the Kvarken archipelago, however.