The group of crocus that bloom in autumn actually contains two separate plants. Some crocuses are fall-blooming, such as the saffron plant used in cooking. However "autumn crocus" is actually a name for colchicum, a crocus-like plant that also blooms in fall. Colchium is a bit larger than crocus, and can tolerate colder temperatures. However, both plants grow from small corms and have narrow, grass-like foliage. Fall-blooming crocuses and colchium should actually be planted well after winter, in midsummer. A July or August planting time will give your fall crocuses enough time to get settled before their blooming season.