A bulb is a large dormant bud, and is a condensed plant when dormant. Bulbs can develop only flowers which were formed within them before they were ripened. The dormant period of a bulb occurs in order to carry it over the dry or cold season.
A good bulb must be fully developed, in good soil, and under good conditions. It must be kept from heating, sweating, or rotting in transit, and must not be kept out of the ground so long as to dry out to an injurious extent. When buying bulbs always take into consideration that cheap bulbs are invariably poor bulbs and that size alone does not count, but adds to the probability that the bulb is mature. Plump, solid bulbs give the best blooms, and if to this is added size, the bulb is ideal.
There are two groups of bulbs: those which should be planted in the fall to produce flowers in the spring, such as tulips, narcissi, and crocuses, and those which should be planted in the spring to produce flowers in the summer and early fall, such as gladioli. (In botanical science in the case of the gladiolus the term is "corm" rather than "bulb.")
Nothing is gained by planting spring-flowering bulbs, such as tulips, narcissi, crocuses, hyacinths, squills, and Spanish irises, before September or October. The reason for planting, then, is that they keep better in the ground, and as they start to root in the fall they begin growth earlier in the spring. It is hardly possible to plant bulbs of this group early enough in the spring to secure any flowers the same season. These bulbs should be planted not earlier than six weeks before the hard frosts. Narcissi may be planted earlier, and it is preferable to plant crocuses early. Crocuses are usually planted in the lawn. An early bloom is desirable; therefore early September planting permits root growth in the fall and the flowers mature and pass before the grass requires cutting. Bulbs, in order to make some root growth in the fall, should not be planted very late. Autumn-flowering sorts, such as the colchicum and the saffron crocus, may be planted in August or early September, if well protected, but if planted in the spring should be set out after danger from frost is past. Narcissi and hyacinths are planted preferably early in October, while tulips, particularly the late-blooming, may wait till November. If the ground begins to freeze hard before the bulbs can be planted it should be kept warm by a litter of straw or leaves. Such a blanket spread over frozen ground early in the winter will enable the heat within the earth to thaw it out and permit quite late planting. If bulbs are planted late it is well to cover them with mulch at once in order that root growth may be made before the cold prevents it. If the bulbs are planted early in the fall, however, the mulch should be applied only after the ground has been frozen to a depth of several inches. Thus excessive top growth will not start prematurely. Gladiolus bulbs should be planted in the spring after the fro sts are over. The period required for such bulbs to mature is about ninety days. Therefore, a succession of bloom can be obtained by planting at intervals of ten days or two weeks. Under expert care, in well-drained soils and with sufficient protection, many gladiolus bulbs can be planted in the fall and thereby insure a very much earlier bloom in the summer. This should at first be tried only with extreme caution, and the plants will need protection from spring frosts.