What is a Plant Corm?

It is very easy to confuse the word corm with corn, but they are two very different things in the plant world. Corn, of course, is the vegetable we eat on the cob or creamed, but a corm is a type of plant stem that is under the ground. Corms are not very long and they are positioned vertically, not horizontally in the soil. They are quite fat or swollen, and look like bulbs. Since they look very much like bulbs, it is sometimes difficult to tell a corm from a bulb. But a corm is solid inside, which distinguishes it from a bulb. If you were to slice a corm and a bulb in half, the corm would be a solid mass whereas a bulb would be composed of layers that are actually a type of leaf. Of course, from the outside, it's hard to tell them apart.

Their purpose is to store nutrients for the plant when weather conditions above ground are not adequate, such as during the winter or even during a drought. This protects the plant until conditions are right again. Each corm has a point or node that produces the growth. Dried leaves form a sort of armor around the corm that gives it some protection against bugs and evaporation of water within the corm itself. The corm is composed of a starchy material that provides the nutrition for the plant.

The node on a corm is where the initial bud and roots will form. The bud or buds will produce a shoot that pushes through the soil and ends up producing leaves and flowers. Interestingly, a corm will grow two different types of roots. The first type are the regular roots that all plants have, the fibrous, spreading roots that collect moisture and nutrients from the soil, but the other type is unique. It's called a contractile root. Its purpose it to pull down on the corm and secure it deeper within the soil. It's a strong root that becomes active during the changes in sunlight and soil at the change of seasons. The contractile root's purpose is to make sure the corm is at a depth in the soil where the temperature is desirable. When the corm is at that depth, the contractile root stops growing.

Some corm plants are taro and the Chinese water chestnut. Both of these corms can be cooked in various ways to get rid of any toxins that are there and to soften up the tough texture. The water chestnuts apparently do not have an toxic substances in them, but the taro corm does.