Closeup showing the presence of six stamens which is typical of the the autumn crocus while the spring crocuses (Crocus spp.) have three.
In the fall of the year autumn crocus sends up white, pink, lavender or purple flowers which are shaped like champagne glasses 5-7 in (12.7-17.8 cm) tall and 2-3 in (5-7.6 cm) across. The tepals (3 petals and 3 sepals that look alike and make up the perianth) are about 2 in (5 cm) long. The flowers arise from a corm which is a storage organ that looks like a bulb without the scales, but is in fact a modified stem that replaces itself each season with a new corm that forms above the previous one. The corm is 1-2 in (2.5-5 cm) in diameter and a large one may produce as many as six flowers. A week or two after the flowers have shown themselves, 5-8 narrow strap-shaped rather fleshy leaves 6-12 in (15-30.5 cm) long emerge and hold themselves more or less erect until they wither away by the following early summer. 'Alboplenum' has double flowers with numerous white tepals. 'Pleniflorum' has double pinkish-purple flowers with 3 in (7.6 cm) tepals.
Location Colchicum autumnal is the most well known and widely cultivated of the autumn crocuses. It comes originally from Europe where it grows wild from southern England, Spain and Portugal to Russia.
Light: Full sun to partial shade in hotter climates. Moisture: Autumn crocus likes a well drained soil that doesn't completely dry out. It doesn't need any moisture in its dormant season (summer), but it likes some water during the flowering period. This species tolerates wetter soils better than any other Colchicum. Hardiness: USDA Zones 4 - 8. C. autumnale is the most cold hardy of the autumn crocuses, and easily survives winter temperatures a little below 0ºF (-17ºC). Propagation: Established clumps may be divided while they are dormant every 3 years or so. Plant corms 4-6 in (10-15 cm) apart and so that the tops are 2-4 in (5-10 cm) below the ground surface; deeper in sandy soils and more shallow in compact soils. They should be planted in summer. Corms that don't get planted in time will bloom anyway!
Autumn crocus can be naturalized in a meadow garden or allowed to grow through grass or other low growing ground covers. In fact, the ground cover is usually necessary to keep the flowers from falling over in rain and wind. For indoor display, the corms can be forced to flower once without any soil. Set them upright on a bed of pebbles in a bowl of water.
Also called naked ladies, the autumn crocus flower stem emerges directly from the ground before the leaves which appear several weeks later.
There are about 45 species of autumn crocuses (genus Colchicum). They look similar to the true crocuses (genus Crocus) in the iris family, but are in fact only distantly related. Crocuses have 3 stamens and autumn crocuses have 6. Crocus leaves are narrow and have a white line down the center; autumn crocus leaves are wider and never have the white stripe. Crocus corms are symmetrical with the shoot on top in the middle; autumn crocus corms are not symmetrical and the shoot comes off a little to the side.
The poisonous compound colchicine, derived from autumn crocus, affects chromosomes and cell division. It is used to treat several kinds of cancer and to induce mutations and polyploidy (increases in the number of chromosomes) in plant breeding programs.
The most common fall blooming crocuses in cultivation are:
1 - 4
1 - 3
1 - 5
1 or 2
1 - 3
1 - 3
For a similar list of spring-blooming crocus, see the Profile of the Dutch crocus Crocus vernus.
All parts of autumn crocus are highly toxic if ingested and contact with the skin may cause irritation.