Dainty, deciduous perennials, (from a corm rather than bulb). Narrow leaves, usually with a silvery central stripe. In spring or autumn, elegant goblet-shaped, flowers, from whites to yellows, purples, pinks and blues. They grow in a wide variety of habitats, from Europe to Asia. C. sativus, saffron, is well known and although it is native to Greece, it was widely grown in Walden, Essex from the 16th century, hence the name change to Saffron Walden.
Although the crocus is an extremely familiar and readily recognisable plant there are no native species in this country. Some flower in autumn but most flower in early spring when they provide a very valuable nectar resource to bumblebees and butterflies that have just emerged from their winter torpor, along with a whole range of other pollinators. Squirrels and small mammals such as mice will uncover and eat the corms and some birds, especially sparrows, peck at emerging flowers to access the protein-rich pollen.