The dormant bulb-like corms should be planted mid- to late- summer for fall blooms. This plant has a slow growth rate, sometimes taking years to germinate and flower. Autumn crocuses are toxic to humans and animals. Some gardeners plant them in the middle of a border, where their foliage will be hidden by other plants and where the sometimes floppy flowers can lean on neighboring plants for support. A small amount of moisture during the summer is necessary to trigger root growth and get the bulbs going. However, ensure the corms are in a spot with sharp soil drainage, or they might rot.
Light
The autumn crocus needs at least a half-day of full sun during its foliage phase. Because this occurs in the spring, it’s OK to plant the autumn crocus under deciduous trees, as the trees won’t have leafed out yet. The flowers will grow fine with some shade.
Soil
Autumn crocuses can grow well in sandy loam or rocky soil. Moreover, they can handle a slightly acidic to slightly alkaline soil pH. The critical factor is good soil drainage.
Water
A moderate level of soil moisture is ideal for the autumn crocus. Soil that is too soggy can rot the plant, while soil that is too dry can desiccate the corm. Water weekly—about one inch per week—during the spring, reducing watering when the foliage dies. Increase water again when the flowers appear.
Temperature and Humidity
There is a relatively narrow growing zone for the autumn crocus compared to other flowering bulbs. Neither frigid winters nor warm winters provide the right conditions for dormancy for the corms. Excessive humidity is not good since it can encourage botrytis, a fungal disease, but sunlight and good drainage can thwart this.
Fertilizer
The autumn crocus grows fine without additional fertilizer. If your soil is poor, you can add some bone meal to the soil mix at planting time.
Types of Autumn Crocus
There are many varieties of the autumn crocus, some include:
‘Innocence’: This plant features clear white blooms and likes partial shade.‘Waterlily’: This variety sports double pink blooms.‘Disraeli’: The checkered pink flowers on this variety make a fascinating addition to the fall garden.‘Autumn Queen’: This type has violet blooms.‘Giant’: This one features white and mauve blooms.
Pruning
As with all flowering bulbs, do not cut back the plant’s foliage. Only prune away the foliage after it has turned yellow. Allow it to die back naturally.
Propagating Autumn Crocus
Autumn crocus can propagate by division or sowing seed. Your autumn crocus will naturally propagate by forming small corms on the main corm. You can take advantage of this by digging up the plant and removing the baby corms in the summer when the plant is dormant. Divide corms every three or four years in the summertime once they begin to spread and get crowded in the same area. Having space between plants is good for ventilating plants and reducing the threat of fungal diseases that often affect overcrowded plants. Here’s how to divide autumn crocus corms:
How to Grow Autumn Crocus From Seed
Division is the best and fastest method for propagation, but you can also sow seeds outdoors in the fall. Autumn crocus seeds need a chill period to trigger germination. Cover the seeds with a scattering of soil on top (1/16 inch deep). Seed germination rates are low and slow. If the seeds eventually sprout, they may take one to two years.
Potting and Repotting Autumn Crocus
You can grow autumn crocuses in pots, but they might not return the next growing season. Use containers that have good drainage holes. Corms like to be planted deeply, so get a pot at least 12 to 16 inches deep. Every few years, thin the corms from a pot that becomes too crowded. Pot them in mid- to late-summer using a standard potting mix, and water when the soil is dry. Place the plant in a sunny location and keep it evenly moist. Repot every few years when the corms become crowded.
Overwintering
For overwintering protection, if you have autumn crocus plants in containers, sink the containers in the ground to overwinter. Underground, the sides of the containers are protected from harsh winds and heating and thawing patterns that more often affect potted plants exposed to wild climate fluctuations, like mild winter days to extreme cold snaps. Or, after the first hard freeze, you can also protect potted autumn crocus plants by placing the pot in a shed, an unheated garage, or a cool basement for winter. If your plants are in the ground, mulch is excellent for keeping the water from evaporating from the soil and preventing weed growth. If you live in a cold weather region, leave the mulch on the ground throughout the winter to protect the corms from the cold. Remove the mulch in the spring.
Common Pests and Plant Diseases
Autumn crocuses can be a tricky species to grow outdoors because of their susceptibility to slug damage. It is rabbit resistant, but snails and slugs might attack the corms. Remove slugs and snails by hand or set traps to catch them. If you mulch your autumn crocus, remove the mulch away from the leaves in spring to reduce hiding places for the slugs. Place organic baits, such as iron phosphate, around the area. The slugs and snails are attracted to this deadly bait (It is safe for kids, pets, and wildlife). You can also use beer traps. Sink a shallow bowl in the soil, so the rim is at the soil line. Fill it with beer. The slugs and snails will drown each evening trying to drink the beer. Autumn crocus corms are also susceptible to fungal infections. Fungal smut or fusarium fungal rot can infect and kill the corms. Keep the soil well drained to prevent these diseases. Soggy conditions make corms vulnerable to fungal infection. Once it takes hold, the damage is hard to rebound from. Be proactive with well-draining soil and avoid overwatering. Divide and move the corms every few years to avoid fungal diseases from cropping up. If you notice any rot or premature foliage blackening, cut off and destroy any affected plants to prevent damage to other plants. Dig up the corm to inspect it. If it’s blackened and mushy, it has rotted. Check the other corms. Destroy the infected corms. If any corms are salvageable, replant them in a new site with fresh soil. Discard the old soil. Mice and voles will tunnel in fall and winter and eat the underground bulbs (corms). A low fence and a castor oil repellent spray will keep them out. When planting the corms, add a small handful of crushed, sharp seashells, oyster shells, or egg shells to the hole. It acts like a barrier and will discourage the animals from tunneling to the bulbs.
How to Get Autumn Crocus to Bloom
You don’t need to deadhead your autumn crocuses as the flowers will fade naturally. They look dainty and pretty in small vases, so that you can pick them for a short indoor display. No matter how ratty the foliage looks in summer, leave all foliage in place until it has completely died back. The foliage is gathering energy and making food from its foliage and storing it in the corm for flower production in the fall. This process is completely necessary for flower production. If your autumn crocus is not flowering and was originally grown from seed, it can take at least four years before flowers appear. Similarly, if you are expecting flowers from divided corms, it can take two years before the corms grow large enough underground to produce flowers.
Common Problems With Autumn Crocus
Autumn crocuses do not have many problems; they are relatively easy to grow but require patience before you see germination or flower production.
Flowers Flop Over
Autumn crocuses prefer full sun. If you notice the flowers have emerged, but many of the flowers have flopped over, they could need more sun. Consider digging up the corms the following summer after the foliage has faded and relocating them to a full sun location.
Brown Spots On Leaves and Stems
Autumn crocuses are susceptible to late spring frosts. You might notice tiny brown spots that turn into larger blotches on the leaves that split or look ragged. Winter protection can help prevent this condition. Lay down a mulch layer over the corms after the first freeze.
Foliage Distorted or Stunted Growth
Insects and pests can make autumn crocuses look sickly, wilted, stunted, or yellowed if not unchecked. Bulb mites are minuscule and hard to see with the naked eye. They have four pairs of legs, piercing-sucking mouth parts, and very compact bodies. Below ground, hundreds of mites will feed on the corm pulp. Dig up and destroy any infested corms. You should soak other unaffected corms from the same soil in hot water (110 to 115 degrees Fahrenheit) for three hours. Similarly, nematodes or worms will feed on underground corms using piercing, sucking mouthparts, hurting the root system, causing corm decay, and eventually killing the plant. Remove and destroy affected corms. To prevent nematodes from infesting your corms in the future, mix leaf mold with the soil when planting corms. Leaf mold encourages beneficial fungi that attack nematodes.
