Two groups of fall-blooming bulbs are commonly known as “autumn crocus,” but in fact, they’re completely unrelated. The first of these is Colchicum (native to Africa and Eurasia), whose other common names include “naked ladies”—due to their habit of blooming months after their leaves have matured and disappeared—and misleadingly as “meadow saffron” (all parts of the plant are poisonous, and shouldn’t be consumed).
The second group is comprised of the true Crocus species (native to Eurasia) that bloom in the fall, including the genuine source of culinary saffron (Crocus sativus). There are also purely ornamental varieties known as “naked boys,” which, like the colchicums, produce their flowers long after the leaves have withered away.
Nekkid or not, both colchicums and fall crocuses provide inspiring fresh flowers at a time when most perennials are entering dormancy, giving a boost to the autumn garden and granting it a new lease on life.
Colchicums prefer a full sun to part shade location in rich, well-drained soil, and like fall crocuses should be planted in late summer or early autumn. Hardy to Zone 4, they produce strap-shaped apple-green leaves in spring, which mature and wither in early summer.
Planting them among groundcovers like ×Heucherella and Lamium cultivars will forestall patches of bare earth in midsummer. Colchicums are more expensive than autumn crocuses, but they size up quickly, so begin with at least three corms (five is better!).
'Album' Meadow Saffron (Colchicum autumnale ‘Album’): 8 cm tall. Each corm produces up to six pure white flowers, which look especially fine when underplanted with periwinkle (Vinca minor and cvs.). More shade-tolerant than Crocus spp. and cvs., colchicums can be planted around the base of mature trees and shrubs.
Bornmueller Colchicum (Colchicum speciosum var. bornmuelleri): 18 cm tall. Each corm produces up to six funnel-shaped bright mauve flowers with white centres. Native to the Caucasus.
'The Giant' Colchicum (Colchicum ‘The Giant’): 25 cm tall. Appropriately named, ‘The Giant’ is perhaps the largest colchicum in cultivation. With a singularly robust constitution, it will spread more rapidly than other cultivars, with each corm producing up to six large, amethyst-violet flowers with white centres.
'Waterlily' Colchicum (Colchicum ‘Waterlily’): 12 cm tall. Looking much like their namesake, the large, fully double lilac-pink blooms of ‘Waterlily’ are one of the last colchicums to bloom in gardens, with each corm producing up to five flowers. Other worthy double-flowered cultivars include Colchicum autumnale ‘Alboplenum’ (white) and ‘Pleniflorum’ (pink). RHS AGM, 1997
Images courtesy of Gardenimport.com