Crocus is a popular genus in horticulture. Out of the ca. 80 species at least 35 are in cultivation in Europe (Mathew 1986). None is native in Belgium. Their determination is often problematic.
The degree of naturalization of species of the genus Crocus often is uncertain. In Belgium they are most often found in lawns in old estates and parks (as feudal plants) and were, in fact, formerly introduced deliberately. They are now more or less naturalized. In other habitats where Crocus-species are sometimes found (road verges, dumps) they often remain strictly ephemeral.
Only four taxa of Crocus have been reported in the wild in Belgium (see key below), although an enlarged knowledge of the genus could yield additional taxa.
1 Flowers predominantly yellowish (often striped purplish outside) === 2
Flowers lilac, purple or white === 3
2 Bulb with covering splitting into rings (never fibrous). Anthers not sagittate, with more or less parallel sides === Crocus chrysanthus
Bulb with fibrous covering. Anthers sagittate at base, wider at base than at apex === C. xstellaris
2 Leaves (1-)2-3(-4) mm wide. Flowers lilac-blue, purplish or reddish-purple with a white perianth-tube (ground-color of the perianth-lobes never white) === Crocus tommasinianus
Leaves 4-8 mm wide. Flowers lilac, purple, violet or white, perianth-tube of the same color or darker than the perianth-lobes === C. vernus
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Kerndorff H., Pasche E. & Harpke D. (2016): The Genus Crocus (Liliiflorae, Iridaceae): Taxonomical Problems and How to Determine a Species Nowadays? Stapfia 105: 42-50.
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