As the plant ages, the stem widens and the centre dies, leaving a ring of separate plants around the outside. Plants such as irises sprout from thick stems called rhizomes that grow sideways beneath the ground. Some-times, the rhizome ends swell into lumps called tubers. Potatoes are tubers. Crocuses have a bulbous base to their stems called a corm.
Tulips have bulbs.
Bulbs look like corms but are made of leaves, like the layers of an onion, rather than a stem. In spring, they send up new shoots. Shrubs Shrubs are smaller than trees, and rather than having a single trunk, they often branch out just above the ground. In very cold or dry places, shrubs may simply be small, spindly versions of trees. Like deciduous trees, deciduous shrubs lose their leaves in winter.