What does corm mean?
A corm is a short, thick, solid underground stem that many flowering plants use as a food-storage and survival organ through winter or dormancy. Unlike a true bulb, which is built of concentric fleshy leaves, a corm is firm stem tissue throughout, usually wrapped in thin, papery remains of old leaf bases. Familiar garden plants that grow from corms include crocus, gladiolus, freesia, and cyclamen. Each growing season the plant draws on the stored nutrients in the corm, often producing one or more new replacement corms on top of the old one while small offsets form at its sides — which is why lifting and dividing corms is a standard propagation technique. The word belongs chiefly to the language of botany and horticulture, so it carries a precise, technical tone rather than everyday familiarity. Knowing the difference between corms, bulbs, tubers, and rhizomes matters to gardeners because each structure stores food differently and behaves differently when planted, divided, or overwintered.
nounA short, thickened, solid underground stem base that stores food and serves as a perennating organ in plants such as crocuses and gladioli, typically covered by dry papery tunics.
- Botany: the short, solid, vertically oriented swollen stem base that functions as an underground food-storage and overwintering organ in plants such as crocus, cyclamen, and gladiolus, usually enclosed by papery dead leaf bases.
"The gladiolus corms were lifted in autumn and stored in a cool, dry shed until spring planting."
"Each autumn she lifted the crocus corms to divide them before replanting."
"Unlike true bulbs, corms are solid throughout, with buds arising at the top rather than among fleshy scale leaves."
The plural follows the regular -s pattern; there are no irregular forms.
"The bed was crowded with dozens of old corms stacked one atop another."
That 'bulb' of your gladiolus probably isn't a bulb at all — slice it open and you'll find no layers, just solid stem: it's a corm, rebuilt fresh every single year.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
How corm is actually used
A technical term used mainly in botany and horticulture; unfamiliar to most general readers, who often assume any round underground storage organ is a 'bulb'. Neutral register, with no figurative or colloquial usage.
Easily confused with corm
A bulb consists of fleshy layered leaves around a compressed stem, whereas a corm is a solid swollen stem with thin papery outer scales.
A tuber is a swollen underground stem or root bearing eyes or buds over its whole surface, while a corm is a compact vertical stem base replaced each season.