Spring-flowering bulbs, such as tulips and daffodils, are familiar to all gardeners. Though not widely planted, the attractive flowers of fall-blooming colchicums and crocuses make them welcome additions to the fall garden.
Colchicums (Colchicum spp.) arise from bulb-like corms. The leaves of most colchicums emerge in early spring and die back by early summer. White to pink to purple, crocus-like flowers appear without foliage in fall. They are also known as autumn crocuses.
Colchicums should be planted immediately upon receipt in late summer or early fall. (If not planted immediately, the corms often bloom during storage.) Plant corms in well-drained soils in full sun to partial shade. Good planting sites include naturalized areas under the filtered shade of large trees and shrubs, in rock gardens, or amongst low-growing groundcovers such as vinca (Vinca minor). For the best visual display, plant colchicums in clumps. Corms should be planted 2 to 3 inches deep and 6 inches apart.
Gardeners can choose from several excellent cultivars. 'Album' produces pure white flowers. 'Alboplenum' has double, white flowers. The flowers of 'The Giant' are 10 to 12 inches tall and violet with a white throat. 'Lilac Wonder' bears large, rosy-purple flowers. 'Pleniflorum' has double, rose-pink flowers. 'Waterlily' produces double, lilac-pink flowers which resemble a water lily.
Colchicums are native to Europe and northern Africa. The scientific name comes from Colchis, an ancient country bordering on the Black Sea, now part of the Georgian Republic, where colchicums are abundant.
The dried corms and seeds of Colchicum autumnale are the source of medicinal colchicum. It is also the source of colchicine which is used in plant breeding to induce polyploids.
Another attractive fall-blooming bulb (corm) is showy crocus (Crocus speciosus). Flowers are violet-blue with yellow anthers and deep orange stigmas. Plant height is approximately 5 to 6 inches. Excellent cultivars include 'Albus' (white flowers), 'Cassiope' (aster-blue flowers with yellow bases), 'Conqueror' (clear, deep blue flowers), and 'Oxonian' (large, dark blue flowers). Showy crocus blooms in late September or October.
Showy crocus performs best in partial to full sun in a well-drained soil. Possible planting sites include rock gardens, naturalized areas, and perennial borders. Plant corms 3 to 4 inches deep in groups of 25 or more.
White to pink to purple, crocus-like Colchicum flowers appear without foliage in late summer or fall.