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 is one example of a small plant that can be challenging to dig unharmed out of a hard, clayey hillside. Corms plants Cultivated plants that form corms include: Alismataceae Sagittaria spp. (arrowhead or wapatoo) Araceae Alocasia macrorrhizos (giant taro) Amorphophallus paeoniifolius (elephant foot yam) Arisaema Colocasia esculenta (taro) Cyrtosperma merkusii (giant swarm 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 Crocosmia (Montbretia) Crocuses, including the saffron crocus (Crocus spp.) Dierama Freesia Gladiolus Some species of irises (Iris spp.) Romulea Musaceae Bananas (Musa spp.) Ensete'' spp. (enset) See also Rhizome Root vegetable Tuber References Plant morphology Plant reproduction Garden plants de:Pflanzenknolle he:פקעת