Bulbs are classified as hardy and tender. Hardy bulbs must be given a period of cold darkness during which they develop strong root systems before growth of foliage is permitted. Tender bulbs cannot survive such a cold or freezing temperature. Technically, not all of the plants discussed in this chapter have true bulbs some grow from corms, rhizomes, tubers, fleshy roots, or other kind of underground stem but as all are handled in much the same way, they are included.

Hardy and tender bulbs in wide variety are easy to grow, and they fit nicely into a greenhouse program. If you start operating your greenhouse in September and get your seed sowing done then, bulbs can be potted and stored in October, and out of the way before it is time to transplant seedlings you will be able to devote yourself to one major task at a time.