Strictly speaking, some so-called bulbs are not bulbs at all, but corms, tubers or rhizomes. A true bulb is an underground swelling of the stem: a mass of leaf-scales within which a new stem and flower later form. A tuber, too, is an underground stem but is solid, not scaly, and able to send out roots from several places. A corm is also solid, but its roots descend from only one place. Rhizomes are creeping, swollen stems, often partly above ground.

Like most plants, after growth has started bulbs prefer a fairly even temperature, and in centrally heated homes this is ensured. Indoor bulbs provide flowers earlier than outdoor ones if the room is not too hot or dry. Because light is vital to all flowers, colours may be less brilliant indoors, so it is important to place the pots in the best light once growth has advanced.

The biggest bulbs are usually the best, because they contain more nutrients. Some are 'prepared' or 'forced'.

This means they have had a specialized heat treatment or a chilling in order to alter their normal time of development, so that it is possible to get them (of certain flowers) to flower in other months of the year. The most common examples of this are Hyacinths, Narcissi and Tulips, and also some Crocuses, Muscari armeniaecum and one or two Scillas.