Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.
I love any plant that blooms in the fall except chrysanthemums. Not that I have anything against chrysanthemums but everyone has them and I like to be different. So I’m adding autumn crocus to my garden this year.
What are Autumn Crocus?
Autumn crocus (Colchicum autumnale) is a fall flowering bulb in the lily family. It is called autumn crocus because it blooms in the fall and its flowers look like crocus but it is not related to crocus which are a member of iris family. Another name for autumn crocus is Meadow Saffron, but it is not saffron or related to saffron which also blooms in the fall. Saffron is a crocus and is edible. Autumn crocus, which looks a lot like it, is extremely poisonous. An easy way to tell them apart is saffron has 3 stigmas and autumn crocus has 6 stigmas.
The leaves appear in the early spring. Each corm produces 3 – 8 leaves. The leaves range in size from 8 – 14 inches. By late spring, they have finished their job of providing food for the corm and die. Do not cut them away until they are completely dead.
The lavender flowers appear in the early fall with no leaves. They are sometimes referred to as Naked Ladies (not to be confused with the Naked Ladies which are related to Amaryllis and bloom in August). Autumn crocus flowers appear in bunches of up to 10 from each corm. Each flower blooms on a stalk that is 4 – 6 inches tall. The flowers last for 2 weeks before dying.
Is Autumn Crocus Poisonous?
The corms of the autumn crocus contain the drug colchicine which in therapeutic doses is used to treat gout and familial Mediterranean fever. The plants and flowers contain lower amounts of colchicine than the corms but it still exceeds a safe dose. Consuming any part of the plant could result in death. There is no known antidote. You should always wear gloves when handling any part of the plant.
The colchicine is also toxic to deer and rabbits, so they don’t eat autumn crocus. If you have a problem with deer or rabbits, these plants are a great addition to your garden.
How to Grow Autumn Crocus
Autumn crocus grows in either full sun or partial shade. The leaves need at least half a day of full sun. Gardeners take advantage of this and plant the corms in one of two places. They either plant them under deciduous trees or in the middle of their gardens.
Deciduous trees lose their leaves in the fall and grow another set in the spring. The foliage of autumn crocus sprouts in the spring before the trees have started growing their new leaves. They enjoy the sun while the trees are growing their leaves. By the time the trees have full size leaves creating shade, the foliage of the autumn crocus is dying.
Planting autumn crocus in the middle of your garden or border, is a strategy used to hide the dying foliage in the spring. The foliage sprouts from the corm in the early spring. By late spring when the leaves are dying and unsightly, other bulbs and perennials planted around them have started to grow and hide the dying leaves.
Autumn crocus grow from corms which are different from bulbs. A bulb is actually a stem with leaves attached to it. That’s why onions have rings. The “rings” are actually the leaves surrounding the bulb. A corm is a form of a root that stores food for the plant.
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Autumn crocus corms are planted in mid- to late summer. Plant them in well-drained, silty soil. If your soil is mainly clay, it will not drain enough and the corms will rot. Consider growing them in raised beds or in containers.
The corms should be planted 3 – 6 inches deep and 6 – 10 inches apart. They will bloom in the fall because the corms were harvested by the nursery after the leaves had grown and died in the spring making food for the corms. Water the corms after you have planted them. After that, there is no need to water them while they are flowering. When they have finished flowering, you can start watering them again, just enough to keep the soil moist until it freezes. In the spring, begin watering again, just enough to keep the soil moist, until the leaves have died and corm has gone dormant.
You can add a thick layer of mulch in the late summer before the flowers appear. The mulch will help the soil remain moist and discourage the growth of weeds.
How to Divide Autumn Crocus
You will notice that your autumn crocus multiplies every year. What is happening is that the mature corms are developing small corms around the outside. Each of those small corms will grow its own plant. Eventually your plants will become too crowded and stop flowering as well. It’s time to dig them up and divide them.
In the summer after the foliage has died, the corms have gone dormant. This is the perfect time to divide them. Carefully dig up the corms. You can gently break off the attached smaller corms and replant them 3 – 6 inches deep and 6 – 10 inches apart, like you planted the original corms.
The smaller corms will take 1 – 2 years before they have grown enough to flower in the fall. For those 1 – 2 years, they will sprout foliage in the spring but no flowers in the fall. Each year the corms are getting bigger and bigger. When they reach a mature size, they will flower in the fall.
© 2020 Caren White
Caren White (author) on August 20, 2020:
The corms are approximately twice the size of crocus bulbs.
Allan Gribbin on August 19, 2020:
What is the mature size of the Croms?
Danny from India on July 22, 2020: