Fig. 10. Bulb of Lilium candidum.
Bulbs often break up or divide themselves into two or more nearly equal portions, as in Lilium candidum, shown one-third natural size in [Fig. 10]. The parts may be separated and treated as complete bulbs for purposes of propagation. This division or separation of bulbs proceeds in a different manner in nearly every species, yet it is so obvious that the novice need not be perplexed by it. Almost any breaking apart of these loose bulbs, if only a “heart” or central axis remains in each portion, is successful for purposes of slow multiplication; but when flowers are desired it is usually inadvisable.
Bulbous plants multiply most easily by means of bulbels—often also called bulbules and offsets—or small bulbs which are borne about a large or mother bulb. In some lilies, as Lilium candidum, the bulbels form at the top or crown of the mother bulb, and a circle of roots will be found between them and the bulb; in others, as L. speciosum and L. auratum, they form on the lower part of the flower stalk. In some species the bulbels are few and very large, or even single, and they bloom the following year. In such cases the bulb undergoes a progressive movement from year to year after the manner of root-stocks, the bulb of one year forming a more or less distinct one above and beyond it which continues the species, while the old one becomes weak or dies. This method of bulb formation is seen in the cut of Lilium pardalinum, [Fig. 11]. In the hyacinth the bulbels form at the base of the bulb.
Fig. 11. Bulb of Lilium pardalinum.
Bulbels vary greatly in size and frequency in different species. Sometimes they are no larger than a grain of wheat, and in other plants they are as large as hickory-nuts. In some species they are borne habitually underneath the scales of the mother bulb. These bulbels are often removed when the mother bulbs are taken up, and they are usually planted in essentially the same manner as the bulbs themselves, although it is desirable to place them, at least for the first year, in a bed or border by themselves. Or if they are especially small and delicate they may be planted in pots or flats and be treated about the same as single eye cuttings. In some lilies the bulbels are allowed to remain attached and the whole mass is planted in the fall in close drills. Sometimes the larger lily bulbels will produce flowers the following season, but they usually require the whole of the season in which to complete their growth. The second fall they are ready to be permanently planted. Bulbels of some plants require a longer time in which to mature into bulbs.