The word bulb is often used to describe true bulbs, corms, tubers, rhizomes and plants with fleshy root systems that can cope with long periods of drought by storing food reserves beneath the ground.
There are, however, clear differences between these five types of plants.
The inside of a true bulb consists of stems and fleshy leaves that have been modified for storage.
In tulip, hyacinth and daffodil bulbs the modified leaves are layered closely around each other, with the outer leaves, which are often dry and brown, forming a tunic around the bulb.
In other bulbs the leaves are not wrapped around each other but overlap, producing a far more succulent bulb.
These bulbs are known as scaly bulbs, and the lily is one of the best known examples.
Individual bulbs usually survive for many years in the ground, during which time the old ones will produce offsets or daughter bulbs and thus create small groups.
Some tulip bulbs are unlikely to produce flowers for a second year, but the bulb will form replacement bulbs, which then flower the following year.
Inside all corms there is a stem that is swollen and adapted to store food.
This forms the base of the new shoots.
Unlike true bulbs, corms appear solid throughout.
After flowering, a new corm, formed at the base of the new stem, will grow on top of the old one and the old corm will die.
Each corm, therefore, has only one season in which to produce a flower.
Small young corms will also form on the basal plate, which is slightly concave.
Crocosmias, gladioli and crocuses are all cormous plants.