Bulbs

Bulbs have several distinctive features that allow you to differentiate them from tubers and corms. Most bulbs such as daffodils, tulips and hyacinths often have a papery skin or tunic on the outside similar to that of an onion. The tunic helps protect the bulb from drying out. Some bulbs like for example lilies do not have a tunic which means that they dry out faster or get more easily bruised.

• Bulbs are more or less rounded with a narrow point at the top. The leaves and flower stems appear from this point.
• At the bottom bulbs are flat, called the basal plate. That is where the roots grow.
• New bulbs, called offsets or daughter bulbs, are formed from the basal plate. The offsets develop into new bulbs themselves.
• Bulbs are made up of layers, called scales, which are modified leaves that store food.

Corms

Corms look very much like bulbs but if you cut them open you will see that they do not have layers, they are solid on the inside. At the end of the growing season, one or more new corms are formed to replace the mother corm. Examples of corms include the crocus, freesia, gladiolus and crocosmia.

Tubers

Tubers do not have a tunic or a basal plate. Tubers have multiple growth points, called eyes. Some tubers have their eyes at the top, like begonias or caladiums. With some tubers it is hard to distinguish the top from the bottom, like anemones and potatoes. If you are unsure which end is the top and which end is the bottom, you can plant them on their side and let the tuber find its way. Tubers usually do not make offsets or produce new tubers. Tubers usually simply grow larger every year and develop more eyes.

Tuberous roots

Tuberous roots are modified, enlarged and specialised roots that store food. The tuberous roots cluster together, joined at the bottom of a stem. The stem contains the new growth point, a piece of the tuberous root alone cannot grow into a new plant. Examples of plants with tuberous roots include dahlias, daylilies and sweet potatoes.