About 16 species of bulbous perennials from Europe excluding Scandinavia and the British Isles (though naturalised in the latter), to Iran with the main centre of distribution in the Caucasus and Turkey. Each bulb usually has two linear to narrowly tongued-shaped leaves and a solitary, pendent, bell-shaped flower composed of six tepals. The three outer tepals are usually pure white and spreading, the three inner ones much smaller and forming a cup with green markings. Although a small genus, it is very complicated taxonomically as all the species have a basic similarity and hybridisation has been extensive. This has resulted in numerous cultivars, many of which can only be identified by a specialist. True species can generally be placed in four groups according to the vernation of the leaves as they emerge from the soil.
Good for providing winter interest on the rock garden, the rarer and less easily grown species and cultivars also in the alpine house. A site with good winter light is best, ideally with partial shade later. Fertile, moist, but well drained soil is essential. Propagation by dividing clumps just as flowers fade ('in the green') or when dormant, in both cases replanting immediately. Seeds are best sown when ripe, but unless collected in the wild, may result in variable hybrids.
1. Leaves flat or applanate as they emerge e.g. G. nivalis. Glaucous or deep green.
2. Leaves revolute (New section by R.D. Nutt), with the margins curled under, e.g. G. reginae-olgae subsp. reginae-olgae. F.C. Stern put this in applanate or flat and C.D. Brickell in 'Flora of Turkey' under explicate, but all explicate and super-volute leaves in non-flowering bulbs have tram-lines (two parallel lines towards the margins) and G. reginae-olgae subsp. reginae-olgae never does. Leaves deep green with a silver channel but can be all glaucous.
3. Leaves explicative with the margins bent under e.g. G. plicatus. The term plicate has also been used, but this means folded into pleats or furrows. Usually dark green with a glaucous or silver channel, but can be entirely glaucous.
4. Leaves supervolute or convolute with the leaves wrapped around each other as they emerge. Leaves can be light green e.g. G. fosteri, or glaucous e.g. G. caucasicus and G. elwesii.
The shape, size and positioning of the green markings on the outer faces of the inner tepals is important for identification at species and cultivar levels. The green lines on the inner face of the inner tepals are a useful characteristic, but one rarely recorded. However, these characters are known to vary slightly from year to year.