Orange (Citrus Aurantium). Rutaceæ.
Orange stocks are grown from seeds, which should be cleaned and stratified in sand or other material, until sowing time. The seeds should not be allowed to become hard and dry. Some prefer to let the seeds sprout in the sand and then sow them in the nursery, but they must be carefully handled. The seeds are usually sown in seed beds, after the manner of apple seeds, and the seedlings are transplanted the next fall or spring into nursery rows. Care must always be exercised in handling orange plants, as they are often impatient of transplanting. Oranges grow readily from cuttings, although cuttage is not often practiced. Green cuttings, handled under a frame, give good results. Mature wood, either one or two years old, can be treated after the manner of long grape cuttings. They must have an abundance of moisture. Layers are sometimes made.
The named varieties are shield-budded upon other stocks. Grafting can be practiced, but it is often unsatisfactory. The nursery stocks are commonly budded in the spring, after having grown in the rows one year, which is two years from the sowing of the seed. If thorn-bearing varieties are to be propagated, a thorn with a bud in its axil is often cut with the bud, to serve as a handle in place of the leaf stalk, which is used in summer budding. Many stocks are used for the orange. The leading ones are sweet or common orange, sour orange (Citrus Aurantium, var. Bigaradia), pomelo (var. pomelana or decumana), Otaheite orange, trifoliate orange (Citrus trifoliata), and various lemons, as the “French” or Florida Rough and the Chinese. For general purposes, the sweet and sour orange stocks are probably the best. The sour stock is obtained from wild seeds, this variety having extensively run wild in Florida from early times. The trifoliate and Otaheite stocks are used for dwarfing or for small growing sorts, as many of the Japanese varieties. The trifoliate orange is also one of the hardiest of the orange stocks, and its use will probably increase upon the northern limit of the orange belt. Old orange trees can be top-budded with ease. It is advisable to cut them back a year before the operation is performed, in order to secure young shoots. In ordinary greenhouse practice, the seedlings of the pomelo make good stocks. They can be established in three-inch pots the first season, and veneer-grafted the next winter.
The method of propagating these plants must in each species be adapted to the habit and mode of growth. The easiest and safest plan for the vast majority is by division, but seeds, cuttings, layers, offsets, and very rarely roots, are also utilized. It is important that artificial means of increase should only be adopted where the individual plants are in robust health. With many orchids the struggle of life under the unnatural conditions we supply, is necessarily severe, and any operation which transforms one weak plant into two or more weaker ones, is to be deprecated. In cases where the only method available necessitates disturbance at the roots, consideration must be paid to the constitution of the species, for some orchids, even when perfectly healthy, strongly resent interference.
Seeds. In no class of cultivated plants is propagation by seeds more difficult and tedious than it is with orchids. In all cases, fertilization must be performed by hand. In England, the length of time required for the capsules to ripen varies from three months to a year. Good seeds form a very small proportion of the whole, and it occasionally happens that the contents of a capsule will not produce a single plant. This, however, as well as the difficulty experienced in England in rearing plants to the flowering stage, is primarily due to the deficiency of sunlight, and in such a bright climate as that of the United States, would not be likely to occur. Various methods of sowing are in vogue, such as sprinkling over pieces of wood and cork or tree-fern stem, and on the top of moss and peat, in which established plants of the same or a nearly related species are growing. The last is probably the best, but it is always advisable to try several methods. Of course, the material on which the seeds are scattered must always be kept moist and shaded. The period between germination and the development of the first root is the most critical in the life of a seedling orchid. After they are of sufficient size to handle they are potted off into tiny pots, and as they gain strength, are given treatment approximating that of adult plants.
Division. Cypripediums may be taken as an example where this is readily done. It is simply necessary to carefully shake off the soil from the roots, and by the aid of a sharp knife, sever the plant into as many pieces as are required. It is always advisable to leave one or more leading growths to each portion. This method may be practiced for the increase of phaius, masdevallia, sobralia, ada, the evergreen section of calanthe, and all of similar habit.
In nearly all those kinds where the pseudo-bulbs are united by a procumbent rhizome, such as occurs in cattleyas, the process is slower. It seems to be natural for these plants to continue year after year, producing a single growth from the old pseudo-bulb. To obtain additional “leads,” the rhizomes should be cut through in early spring, two or three pseudo-bulbs being reserved to each piece. A bud will then push from the base of each pseudo-bulb nearest the division, and a new lead is formed. The pieces should not be separated until this is well established, and three years may sometimes be required. Lælia, catasetum, cœlogyne, lycaste, cymbidium, zygopetalum, odontoglossum, oncidium, miltonia, etc., are treated in this manner.
Cuttings.—This method is available for those kinds with long, jointed stems, like dendrobium and epidendrum. Just before the plants commence to grow, say in February, the old pseudo-bulbs are cut up into lengths, and laid on a moist, warm surface, such as on a pan of moss in a propagating frame. Young offshoots will shortly appear at the nodes, and when large enough are potted off with the old piece attached. This plan may be used also for barkeria and microstylis.
It is well to remember that in any method of propagation where the pseudo-bulb is divided, the vigor of the young plant is proportionate to the amount of reserve material supplied it. However suitable the external conditions may be for growth, it is for some time entirely dependent for sustenance on the old piece from which it springs. Dendrobium Phalænopsis is a case in point. If a pseudo-bulb is cut into say three pieces, it will take at least two years for the young plants to reach flowering strength, but frequently by using the entire pseudo-bulb, we can get in a single year a growth quite as large as the old one.