Definition - What does Corm mean?

A corm is a swollen underground part of plant where nutrients and water are stored against a future need. Many different plans have corms, and these can be confused with rhizomes, tubers and other underground plant structures.

MaximumYield explains Corm

When it comes to root system and physical structure, plants can vary dramatically. Some have ordinary roots. Others have no roots at all. Some grow from bulky underground structures like bulbs, rhizomes, tubers and corms. You might be familiar with what a bulb is, but what about a corm? Not entirely sure what separates corms from other underground structures?

A corm is not all that different from a bulb or a rhizome, at least in terms of function. It does differ in shape. Generally, a corm is round, with the plant growing out of an inset indention at the top of the structure. Roots spill out from the top of the corm into the ground, while the structure itself is used to store nutrients and water against future need.

Both the crocus and the snake lily are examples of plants that grow from corms. Note that corms can be small or large. For instance, a crocus corm is usually about an inch across. In comparison, a mature snake lily might have a corm that measures nine inches across.

How does a corm differ from a bulb? Really, it’s about overall construction. Corms are usually solid, but bulbs have multiple layers, like an onion. Tubers differ in that buds sprout from their bodies – think potato eyes sprouting, and rhizomes differ in that they’re really just swollen stems that grow across, rather than up and down.

Ultimately, corms, rhizomes, bulbs and tubers serve similar purposes, though. And, gardeners often lump them all together under the generalized heading of “bulb”, although that’s not actually correct.

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