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.