The British Isles is often cited as containing the majority of the world’s population of this species, which has helped drive concern over its continued survival here in the face of aggressive hybridisation.
In terms of area, or extent of occupancy, the extra-British western European range is broader but the species is sparsely and very unevenly distributed throughout that and never achieves the density of population seen in the British Isles.
Although the species can spread locally very efficiently by vegetative means (small bulbils forming around the main bulb), population genetic studies have shown that the major mechanism of reproduction is sexual, by seed, which is abundantly produced in most years.