How to Grow Fall Flowering Crocus
Fall flowering crocus are a fun, late-season surprise in the garden. Most gardeners are familiar with the spring crocus, but the fall varieties offer the same bright white, blue, purple, and pink cup-shaped flowers, at a time of year when other blooms passed. Grow fall-flowering crocus to add color to rock gardens, perennial borders, or under flowering trees.
When & Where to Plant Fall Flowering Crocus
Light: Fall flowering crocus bloom best in full sun. The lower growing varieties, such as the edible saffron crocus, will flower in part shade, but to a lesser degree. The taller colchicum autumn crocus will flower in part sun, but can get floppy.
Soil: Fall flowering crocus grow best in well-drained, silty soil. Avoid heavy clay soils or those that drain water poorly. These will result in the bulbs (corms) rotting. Amend the soil with compost, sand or peat moss and raise the beds to improve water drainage. Fall crocus like a neutral to slightly alkaline pH, so add lime as needed based on a soil test.
Spacing: Space small varieties of fall flowering crocus bulbs (corms) 3 inches apart. Space larger varieties 6 to 10 inches apart. They both look best if planted en masses.
Planting: Plant fall flowering crocus bulbs (corms) in late summer or early fall.
How to Grow Fall Flowering Crocus Throughout the Season
Growth Habit: Fall flowering crocus are divided into two groups. Small varieties, such as the saffron crocus, have bulbs, plants and flowers the same size as the spring flowering crocus. They first send up flowers in early autumn followed by grass-like leaves usually later in fall.
The larger sized fall flowering crocus are colchicums. They bloom from September to November, depending on the variety. They send up large, goblet-like blooms up to 6 inches tall without leaves. In spring, they send up broad leaves.
Staking: No staking is needed for the low growing fall flowering crocus. Colchicums growing in part shade can benefit from some propping up with a low cage, since the flower stalks may get floppy.
Watering: Water fall flowering crocus in late summer after planting, only if the soil is dry. It's best to avoid watering while they're flowering. Keep the soil evenly moist after flowering until the ground freezes and again in spring until they go dormant in summer.
Fertilizing: Amend the soil at planting with compost and, based on a soil test, bone meal or an organic high phosphorous fertilizer to encourage bulb growth and flowering. Each fall, add a 1- to 2- inch thick layer of compost and a small amount of a granular bulb fertilizer to the planting area.
Mulching: Mulch fall flowering crocus in late summer with a 1- to 2-inch thick layer of shredded bark mulch or chopped leaves. The mulch will conserve soil moisture, prevent weed growth and prevent the soil from splashing unto the delicate fall crocus flowers. Remove the mulch after flowering to prevent the soil from staying too wet in winter. In cold areas, leave the mulch on in fall and winter to protect the bulbs from the cold.
Fall Flowering Crocus: End of Season Care
Trimming & Pruning: Let the flowers naturally fade in autumn. Depending on the type of fall flowering bulbs you're growing, let the foliage in fall or in spring naturally yellow and die. The foliage rejuvenates the bulbs.
Dividing & Transplanting: New corms are formed each year on top of the old ones, which allows clumps to increase in size. Both Colchicum and Crocus are very long-lived and benefit from dividing regularly.
Fall flowering crocus bulbs will slowly expand and after 3 to 4 years can be divided to produce more bulbs. Small bulblets (cormlets) will form around the edge of the mother bulb. In summer while the bulb is dormant, dig up the bulb clumps, separate out the bulblets and replant in a location with similar growing conditions. The bulblets will take 1 to 2 years before they're large enough to flower.
Pests/Disease: Fall flowering crocus do have some pests that like the bulbs and flowers as much as we do. Rabbits will munch on the flowers and foliage. A low fence and repellent sprays will keep them out. Mice and voles will tunnel in fall and winter and eat the underground bulbs (corms). When planting, add a small handful of crushed, sharp seashells, oyster shells, or egg shells to the hole. This will discourage them from tunneling to the bulbs. Spraying a repellent containing castor oil also may help ward them off.
Slugs and snails will eat the foliage, especially in spring for the large flowering types. 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 bait, but once they eat it, the iron phosphate will kill them. 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 3/4th with beer. Each evening the slugs and snails will drown trying to drink the beer. Clean out the bowl each morning. Keep your dogs away from the beer trap because they might like to taste it too.
Fungal rot diseases, such as fusarium, can attack the bulbs. Keep the soil well drained to prevent these diseases. Also, dividing and moving the bulbs after 4 years of growing in one area, will help avoid these diseases building up.
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