Corm

Not to be confused with

Corn.

Corm, bulbo-tuber, or bulbotuber is a short, vertical, swollen, underground plant stem that serves as a storage organ that some plants use to survive winter or other adverse conditions such as summer drought and heat (perennation).

The word cormous usually means plants that grow from corms, parallel to the terms tuberous and bulbous to describe plants growing from tubers and bulbs.^[1]

A corm consists of one or more

Internally, a typical corm mostly consists of parenchyma cells, rich in starch, above a circular basal node from which roots grow.^{[citation needed]}

Long-lived cormous plants vary in their long-term development. Some regularly replace their older corms with a stack of younger corms, increased more or less seasonally. By splitting such a stack before the older corm generations wither too badly, the horticulturist can exploit the individual corms for propagation. Other species seldom do anything of that kind; their corms simply grow larger in most seasons. Yet others split when multiple buds or stolons on a large corm sprout independently, forming a tussock.^{[citation needed]}

Corms can be dug up and used to propagate or redistribute the plant (see, for example, taro). Plants with corms generally can be propagated by cutting the corms into sections and replanting. Suitably treated, each section with at least one bud usually can generate a new corm.

Corms are sometimes confused with true

Corms can form many small cormlets called cormels, from the basal areas of the new growing corms, especially when the main growing point is damaged. These propagate corm-forming plants. A number of species replace corms every year by growing a new corm. This process starts after the shoot develops fully expanded leaves. The new corm forms at the shoot base just above the old corm. As the new corm grows, short stolons appear that end with the newly growing small cormels. As the plants grow and flower, they use up the old corm, which shrivels away. The new corm that replaces the old corm grows in size, especially after flowering ends.

The old corm produces the greatest number of cormels when close to the soil surface. Small cormels normally take one or two more years of growth before they are large enough to flower.

Cormels do have a reproductive function, but in the wild they also are important as a survival strategy. In most places where

Those growing from the bottom of the corm are normal fibrous roots formed as the shoots grow, and are produced from the basal area at the bottom of the corm. The second type are thicker layered roots called contractile roots that form as the new corms are growing. They pull the corm deeper into the soil. In some species contractile roots are produced in response to fluctuating soil temperatures and light levels. In such species, once the corm is deep enough within the soil where the temperature is more uniform and there is no light, the contractile roots no longer grow and the corm is no longer pulled deeper into the soil. In some other species, contractile roots seem to be a defence against digging animals and can bury the corm surprisingly deeply over the years. Wurmbea marginata^[4] is one example of a small plant that can be challenging to dig unharmed out of a hard, clayey, hillside.

Cultivated plants that form corms include:

• Alismataceae
  • Sagittaria spp. (arrowhead or wapatoo)
• Araceae
  • Alocasia macrorrhizos (giant taro)
  • Arisaema
  • Colocasia esculenta (taro
    )
  • Cyrtosperma merkusii (giant swamp taro)
  • Xanthosoma spp. (malanga, cocoyam, tannia, and other names)
• Asparagaceae
  • Bessera
  • Brodiaea
  • Dichelostemma
  • Milla
  • Tecophilaea
• Asteraceae
  • Liatris
• Colchicaceae
  • Colchicum
• Cyperaceae
  • Eleocharis dulcis (Chinese water chestnut)
• Iridaceae
  • Montbretia
    )
  • Crocuses, including the saffron crocus (Crocus spp.)
  • Dierama
  • Freesia
  • Gladiolus
  • Some species of irises (Iris spp.)
  • Romulea
• Musaceae
  • Bananas (Musa spp.)^[5]
  • Ensete spp. (enset)

• Rhizome
• Root vegetable
• Tuber