Plectocomia. Palmæ.
Seeds. May be increased by suckers.
Pleroma, Lasiandra, including Melastoma. Melastomaceæ.
Seeds. Propagated mostly by cuttings of growing shoots in a close frame at any season.
Plum (Prunus, many species). Rosaceæ.
There are so many species of plums in cultivation, and the varieties of the same species are often so different in constitution and habit, that it is difficult to give advice concerning their propagation. All the species grow readily from fresh, well-ripened seeds. The pits should be removed from the pulp and then stratified until spring. If they are allowed to freeze, the germination will be more uniform, as the pits will be more easily opened by the swelling embryo. Plum pits are rarely cracked by hand. The strong-growing species and varieties, especially southwards, will give stocks strong enough to bud the first season; but the weaker ones must stand until the next season after the seeds are planted. In all the northern states, however, plum pits are usually sown in seed-beds, in the same manner as apple and pear seeds. The seedlings are taken up in the fall, and the following spring set out in nursery rows, where they are budded in August.
Plums are extensively grown from suckers, which spring in great numbers from the roots of many species. In France this method of propagation is largely used. So long as graftage does not intervene, the sprouts will reproduce the variety; and even in grafted or budded trees this sometimes occurs, but it is probably because the tree has become own-rooted from the rooting of the cion. It is a common notion that trees grown from suckers sprout or sucker worse than those grown from seeds. Layers are also extensively employed for the propagation of the plum. Strong stools (page 35) are grown, and the long and strong shoots are covered in spring throughout their length—the tips only being exposed—and every bud will produce a plant. Strong shoots of vigorous sorts will give plants strong enough the first fall to be removed into nursery rows. Mound-layering is also employed with good results. Root-cuttings, handled like those of blackberry, grow readily, but some growers suppose that they produce trees which sucker badly. Many plums grow readily from cuttings of the mature recent wood, treated the same as long grape cuttings. This is especially true of the Marianna and its kin (P. umbellata), which are grown almost entirely from cuttings. Some sorts of the common garden plum (P. domestica) also grow from cuttings.
Plums are worked in various ways, but ordinary shield-budding is usually employed in late summer or early fall, as for peaches and cherries. Root-grafting by the common whip method is sometimes employed, especially when own-rooted trees are desired ([page 78]). In the north and east, the common plum (P. domestica) is commonly worked upon stocks of the same species. These stocks, if seedlings, are apt to be very variable in size and habit, and sometimes half or more of any batch, even from selected seeds, are practically worthless. Stocks from inferior or constant varieties are therefore essential. Such stocks are largely imported; but there are some varieties which can be relied upon in this country. One of the best of these domestic stocks is the Horse plum, a small and purple-fruited variety of Prunus domestica, which gives very uniform seedlings. This is largely used in New York. The French stocks which are in most common use are St. Julien and Black Damas. The Myrobolan (P. cerasifera) is much used in California for standards, but in the east it makes dwarf trees. The peach is often used as a plum stock, and it is valuable in the south, especially for light soils. In the north plum stocks are better. Almond stocks, especially for the French prune and for light soils, are considerably used in California. The apricot is sometimes employed, but results appear to be poor or indifferent, on the whole. Prunes thrive upon the above stocks also.
Various stocks dwarf the plum. The chief dwarf stock at present is the Myrobolan. This is usually imported. It is easily grown, either from seeds or cuttings. The Mirabelle, a foreign stock, is sometimes used. The many species of native plums, of the Prunus Americana and P. angustifolia (Chickasaw) types, are good stocks for dwarf or intermediate trees. In most cases, the bud or graft grows luxuriantly for two or three years, and thereafter grows rather slowly. It is best to bud or graft low upon these stocks. The Marianna is at present the most popular native stock.