Perennial rosette hemicryptophyte. Rosettes with a short, up to 5 mm, erect conical/discoid axis, bearing a succession of closely spaced leaves, and giving rise to intercalary primordia which may alternatively differentiate into adventitous roots, inflorescences, vegetative buds, or sessile, tangentially flattened, winter bulbils. Leaves, sometimes fleshy, incurled, 1-5(-10) cm long, 0.3-2 cm broad, oblanceolate, oblong-ovate to elliptic, obtuse or subacute, sometimes narrowing into a petiole-like basal region which may represent almost half of the length, finely toothed or crenulate to entire, green, somewhat glistening above when mature with, in the type subspecies, whiteor sulphur-coloured farina on abaxial surface; farina on both surfaces of unexpanded leaves, and of apetiolate leaves in overwintered newly expanding rosettes; farina sometimes initially present on adaxial surface of expanded leaves but subject to removal by weathering. Cotyledons and leaves with scattered unicellular capitate glandular hairs on upper surfaces; similar hairs also on hypocotyl. Scape(s) (mostly absent in one British population) originating among leaf bases of rosettes, thick striate 0-3 cm tall, or thinner 2-20(-30) cm tall reflecting an intrapopulation genetic polymorphism (a varietal name, acaulis Ahlq., has been applied). Scape sparsely glandular, farinose entirely when young, distally only later, bearing one umbel (or unusually two umbels 'candelabra-like' on the same axis) with few or many (< 30) flowers or flower buds not all of which may mature, flexible during flowering, rigid during fruiting. Pedicels c. 5 mm, slender, slightly spreading, becoming twice as long as bracts, farinose. Bracts 2-8 cm long, narrow lanceolate, to subulate, acute or acuminate, broadened at the markedly gibbous base, more or less farinose. Calyx cylindric or urceolate becoming cuplike in fruit, 3-6 x 2 mm, farinose both within and without; usually five-angled and toothed, with the teeth obtuse, or more rarely acute, often tinged with purple or black. Corolla annulate, with 5-partite limb 8-16 mm across with flat segments mutually distant, but not so in all populations, cuneate, or cordate (with spaces between petals obscured), bifid, coloured lilac, deepest crimson, shades of purple, rarely bluish or white, deep yellow in the throat, and with tube 5-8 mm long, greenish-yellow equalling or slightly exceeding the calyx. Heterostylous; stamens epipetalous set either in the upper part of the tube (thrum-eyed flowers), or in the middle of the tube (pin-eyed flowers), these on separate clones; the former flowers with style half as long as the calyx the latter with the style reaching almost to the annulus. Capsule cylindrical, obtuse, usually much exceeding the calyx, 5-9 mm long, green, farinose becoming shiny brown, opening apically through splitting into five (unusually more) triangular, obtuse 1-mm long segments. Seeds c. 0.5 mm diameter; mean seed weights for populations ranging from 48.4 .Lg to 76.3 [Lg (Tremayne & Richards 2000), borne on axile placenta, may appear coffin-shaped in transverse aspect, ovoid to quadrate angular when released, golden brown when mature, minutely vesicular-surfaced vesicles are single cells, smaller than those of its near relative the Scottish endemic P scotica Hook. Root