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 varieties 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.
Tender and half-hardy bulbs, though sometimes grown in cool temperatures, cannot stand the freezing or very cold temperatures needed by hardy bulbs. Tender "bulbs" include not only true bulbs, but plants that grow from other types of underground stems, as rhizomes, corms, tubers, and fleshy roots. In many instances, tender bulbs can be potted and grown at times of the year other than their natural season, provided, of course, you can obtain the bulbs at off-times of the year and can provide their needed conditions.
Tender bulbs have two appealing characteristics: the many different kinds of flowers, from the tremendous lily-like blossoms of amaryllis to the delicate, deliciously fragrant freesia; and the fact that they can be potted and started immediately into growth. Some, as the paper white narcissus and the dainty French-Roman hyacinths, grow and produce flowers quite rapidly.
Most tender and half-hardy bulbs should be potted in a mixture of two parts garden loam, one part peatmoss, and one part sand, with a little bonemeal added to promote continuous growth. Screening the soil mixture through a half-inch mesh is beneficial, as the roots must be able to move through the soil without obstructions. Potting procedure is the same as described earlier for hardy bulbs. Place some drainage material in the bottom of the pot, add soil mixture, plant the bulbs, and water thoroughly. Keep the pots under the bench for a week or two, then move them to the bench to good light. Proper watering is important. After the initial thorough watering, water sparingly until top growth is well started; then increases the supply of water to insure continuous development of the foliage and flowers.
Another nice thing about some of these tender bulbs is that they do not have to be grown in soil, but can be set in containers of pebbles filled with water. The pebbles support the bulb, which should be placed so that half the bulb extends above the pebbles; if the container is kept filled with water to the top of the pebbles, sufficient moisture will be available for substantial root growth. Add a piece or two of charcoal to the pebbles to keep the water "sweet."
Paperwhite narcissus and French-Roman hyacinths, especially, can be grown in this manner. A few containers planted in this fashion placed on the shelves in your greenhouse lend a daintiness and fragrance that is most appealing; or you can move them into your home as soon as they have been forced into bloom.
Tender bulbs vary considerably in their growth habits some remain evergreen, some even flower almost all year, and some require definite dormant periods. The care for each is found in our alphabetical guide.
I suggest that you try only one or two kinds of tender bulbs from the following list your first season (in addition to your hardy bulbs) not that they are difficult to grow, but to allow for a different selection the following season to add interest and variety to your gardening program.