Corms for Beginners
Crocus and Gladioli are easy plants to grow from corms. Plant some ‘Glads’ in March for summer flowering and some Crocus in Autumn for next spring. You may even find some Crocus in pots that will flower now and can then be planted out for next spring.
What is a Corm?
Corms are (underground) stems that are internally solid tissues with a fibrous outer. This differentiates corms from bulbs, which are made up of layered fleshy scales that are modified leaves. As a result, when a corm is cut in half it is solid, but when a true bulb is cut in half it is made up of layers. The Corm is the food store for the next generation of plants.
Crocus and Gladioli are two of the best known plants grown from corms. Also Cyclamen, Bananas, Diermia, Crocosmia, Liatris and Freesia are corm based plants.
Roots growing from the bottom of the corm are normal fibrous roots are formed as the shoots grow. The second type of roots are thicker layered roots that form as the new corms are growing, they are called contractile roots and they pull the corm deeper into the soil.
Corms of some species of plants are replaced every year by the plant with growth of a new corm at the shoot base just above the old corm. As the plants grow and flower, the old corm is used up and shrivels away. The new corm that replaces the old corm grows in size, especially after flowering is done.
Corms can form many small cormlets called cormels at the base of the plant and these can be grown on for subsequent seasons. They grow true to the parent plant and are a way of increasoing stock. A corm can be cut into wedges and grow a new plant as long as there is a bud on each part.
A description and graphic of a good corm is available from the University of Illinios
