The scope and diversity of this amazing genus of bulbs in Liliaceae (or Calochortaceae if they are placed in a family on their own) is still little appreciated by the skilled growers of Eurasian bulbs, who have developed in recent decades. About 100 taxa are distributed from British Columbia in the North to Guatemala in the South. While they extend East to the Dakotas, the centre of diversity is in California, where almost half of the known species, most of them endemic, occur. The range of species we now offer is possibly the most extensive ever listed. Since we first visited western North America in 1989, we have seen most species in their natural habitats, collected seed from the majority and are now growing them in Wales. This would not have been possible without the kindness and generosity of other enthusiasts who have shared the vast amount of their composite knowledge with us. We acknowledge our gratitude for past assistance to Wayne Roderick, Stan Farwig and the late Vic Girard, Georgie and the late Jim Robinett, David King, Frank Callahan and Boyd Kline, as well as the ongoing help we continue to receive from John Andrews and Greg Greger, all of whom have made our list possible.

Seeds from most of the winter and spring growing species from the western USA are listed by us, though we lack the summer-growers which extend south through Mexico to Guatemala. Cultivation can be best learned from noting the habitats of each collection. There are no generalisations to be made about cultivation, in spite of some dreadfully reprocessed 'received wisdom' we have seen published. Dr. Sylvia Martinelli's recent accounts in several UK publications are reliable but it must be remembered that she writes from experience of a relatively restricted number of mainly Californian species. The growth-cycles of all the western Americans fit in perfectly well with winter-growing Eurasian species. The Mexican species from summer-rainfall areas are another matter and they should be overwintered completely dry with watering commencing in spring. The early-flowering, low altitude Fairy Lanterns match the Mediterranean growth-cycle of many bulbs. The late-flowering Mariposas and more eastern steppe-species might be more compatible with such groups as the Oncocyclus and Regelia Irises. The species from the cold, dry climates of the Great Basin and further east are proving the most difficult to cultivate in milder, wetter climates. We suspect they may be best left unwatered until later in winter, like some of the Central Asian Fritillaria species. Even the later-flowering Californians may be best left until mid-winter before watering, though we have noted that root-growth starts to become active with falling temperatures. We are provisionally convinced that these late-flowering species need little further watering after the first buds open. The quality of the bulbs will be much better.

Nomenclature : The standard account of this genus remains ‘A Monograph of the Genus Calochortus’ by M. Ownbey (1940). It is the basis for the account in ‘The Jepson Manual’ (1993), which deals only with Californian species, and the 'Flora of North America' (Flora Online : http://flora.huh.harvard ). Both Ownbey and Hoover corrected or updated inaccuracies in the 1940 monograph and further new species have been described. Frank Callahan’s account in ‘Bulbs of North America’ (2001) is by far the best modern reference for names.

Further information : The chapter on ‘The Genus Calochortus’ by Frank Callahan in ‘Bulbs of North America’ (2001), ed. Jane McGary, gives an outstanding overview of the entire genus including the Mexican and Guatemalan species. It is worth acquiring this book for this chapter alone. With the demise of both Jim Robinett and Vic Girard, Frank is without question the unrivalled authority on this genus in its natural habitats. Frank, however, is not a gardener and his brief comments on cultivation are not always very helpful and come into the ‘received wisdom’ category.