CHAPTER II.

SEPARATION.

=Separation.=--The act or process of multiplying plants by means of naturally detached asexual organs, or the state or condition of being so multiplied.

Separation is effected by means of bulbs, bulbels, bulb-scales, bulblets, corms, tubers, offsets, crowns and sometimes by buds.

Bulbs of all kinds are specialized buds. They are made up of a short and rudimentary axis closely encased in transformed and thickened leaves or bulb-scales. These thickened parts are stored with nutriment which is used during subsequent growth. Bulbs occur only in plants which are accustomed to a long period of inactivity. Many bulbous plants are peculiar to dry and arid regions, where growth is impossible during long periods. A bulb is, therefore, a more or less permanent and compact leaf-bud, usually occupying the base of the stem underground and emitting roots from its lower portion. Bulbs are conveniently divided into two great classes--the scaly, or those composed of narrow and mostly loose scales, as in the lily, and laminate or tunicate, or those composed of more or less continuous and close-fitting layers or plates, as in the onion.

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.

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.

Bulbels are often produced by an injury to the bulb. Growth of stem and leaves is prevented or checked and the energy is directed to the formation of minute buds, or bulbs, in the same manner as adventitious buds form upon a wounded stem. Advantage is taken of this fact to multiply some bulbous plants, and in the case of the hyacinths, at least, the mutilation of bulbs for this purpose is practiced to a commercial extent. Hyacinth bulbs are cut in two, or are slashed in various ways. The favorite method is to make two or three deep transverse cuts into the base of the bulb. The strongest bulbs should be chosen and the operation is performed in spring or early summer when the bulb is taken up. The bulbs are sometimes hollowed out from the under side for half or more of their length. This operation is sometimes performed later in the season than the other, and precaution should be exercised that the bulbs do not become too moist, else they will rot. Hollowed bulbs should be well dried before being planted. Both methods of preparing hyacinth bulbs are shown in Figs. 12 and 13 which are adapted from Gardeners' Chronicle. Fig. 14 shows a portion of the base of a cross-cut bulb, with the adventitious bulbels. The mutilated bulbs are stored during summer, and are planted in fall or spring. The wounded bulbs produce very little foliage, but at the end of the first season the bulbels will have formed. The bulbels are then separated and planted by themselves in prepared beds. Several years are required for the bulbels to mature into flowering bulbs. Some of the strongest ones may produce flowering bulbs in three years, but some of them, especially those obtained from the hollowed bulbs, will not mature short of six years. This method of propagating hyacinths is confined almost entirely to Holland.

The scales of bulbs are often employed to multiply scarce varieties. From ten to thirty of the thicker scales may be removed from the outside of the bulb without serious injury to it. These are treated in the same manner as single eye cuttings. They are usually handled in flats or propagating-frames, and are pressed perpendicularly into a light and loose soil--half sharp sand and half leaf-mould--for nearly or quite their entire length, or are scattered in damp moss. Keep the soil simply moist, and for hardy and half-hardy species keep the temperature rather low--from 45° to 60°. Slight bottom heat may sometimes be given to advantage. In from three to ten weeks a little bulbel, or sometimes two or more, will appear at the base of the scale, as shown in Fig. 15.

These pots or flats may be plunged out-doors during summer if the planting was done in winter, or the scales may be potted off or transferred to the open border as soon as rootlets have formed. It is the common practice with most hardy species to allow the scales to remain in the original flats during summer and to cover them the next fall, allowing them to remain out-doors over winter. The succeeding spring they are shifted into a bed or border, and by the next fall--having had two summers' growth--most species will be ready for permanent planting in the flower border.

A _bulblet_ is a small bulb borne entirely above ground, usually in the axil of a leaf or in the inflorescence. Familiar examples occur in the tiger lily and in "top" onions. In the former instance the bulblets are direct transformations of buds, while in the onion they are transformed flowers. It is impossible to draw any line of separation between bulblets and buds. In some plants, certain buds detach themselves and fall to the ground to multiply the species. Sometimes these buds vegetate before they fall from the plants, as in the case of various ferns. For purposes of propagation, bulblets are treated in the same way as bulbels, and like them, they reproduce the variety upon which they grow. They will develop into full grown bulbs in from one to three years, according to the species.

A _corm_ is a bulb-like organ which is solid throughout. Familiar examples occur in the gladiolus and crocus. Cormous plants are multiplied in essentially the same manner as bulbous species. As a rule, a new corm is produced each year above the old one, and this commonly bears flowers the following season. This renewal is well shown in the gladiolus, Fig. 16. The illustration shows a gladiolus bottom, half size, when taken up in November. At the base are seen the withered remains of the corm which was planted in the spring, and above it the new corm which will furnish bloom the following season. A number of _cormels_ or "spawn" have also appeared. These may be planted out in a border or bed and will produce mature bulbs in one or two seasons. The larger ones, under good treatment, will often produce bulbs an inch in diameter the first season. Some growers keep the cormels a year and a half before planting them out, as they are thought to vegetate more evenly under such treatment; in this case they should be placed in sand to prevent too great drying out.

Adventitious cormels may be produced by various methods of wounding the mother corm, and this practice of exciting them is often necessary, as some varieties do not produce cormels freely. Each bud on the top or side of the corm may be made to produce a separate corm by cutting a deep ring around it, so as to partly divide it. Or the corm may be directly cut into as many separate pieces as there are buds or eyes, after the manner of cutting potatoes, but these pieces are usually handled in flats where temperature and moisture can be controlled. Almost any injury to such vigorous corms as those of the gladiolus and crocus will result in the production of cormels, if care is taken that the corms do not become so cold and wet that they will rot.

A _tuber_ is a prominently thickened portion of a root or stem, and it is usually subterranean. The potato, sweet potato and dahlia furnish good examples. Tuberiferous plants are multiplied by planting these tubers whole, or the tubers may be cut into small portions as described in Chapter IV, in the descriptions of cuttings. In hardy species, the tubers may be allowed to remain in the ground during winter, but they are generally dug in the fall and stored in a dry and cold place, but where they will not freeze.

An _offset_ is a crown or rosette of leaves, usually borne next the surface of the ground, which detaches itself and forms an independent plant. The best examples occur in the house-leeks, plants which are more familiarly known as "hen and chickens" and "man and wife." These offsets take root readily, and in propagating there is no other care necessary than to remove and plant them.

A _crown_ is a detachable portion of a root-stock bearing roots and a prominent bud. Rhizomes or root-stocks multiply individuals and extend the distribution of the species by means of a progressive movement of the crowns. The root-stock grows during summer, and at the end of the season each branch develops a strong terminal bud which usually produces a flowering stem the following season. The root-stock gradually dies away at its old extremity, and in a few years a single individual gives rise to a considerable patch. This is well shown by the common May-Apple or podophyllum.

In some species these crowns are removed in the autumn and are planted and handled in much the same manner as bulbs. The crown or pip of the lily of the valley, shown half size in Fig. 17, is obtained in this manner.