Onion (Allium Cepa). Liliaceæ.
Onions are mostly grown from seeds, which must be sown as early as possible in spring; or in the south they may be sown in the fall. They are also grown from “tops,” which are bulblets borne in the flower cluster. These are planted in the spring, or in the fall in mild climates, and they soon grow into large bulbs. “Sets” are also used. These are very small onions, and when planted they simply complete their growth into large bulbs. Sets are procured by sowing seeds very thickly in poor soil. The bulbs soon crowd each other, and growth is checked, causing them to ripen prematurely. Good sets should not be more than a half inch in diameter. Very small onions which are selected from the general crop—called “rare-ripes”—are sometimes used as sets, but they are usually too large to give good results. Some onions—the “multiplier” or “potato onions”—increase themselves by division of the bulb. The small bulb, which is planted in the spring, splits up into several distinct portions, each one of which will multiply itself in the same manner when planted the following year.
Onobrychis (Saintfoin). Leguminosæ.
Seeds, sown in spring where the plants are to remain.
Onosma (Golden Drop). Boragineæ.
Seeds, sown in the open in spring. Perennial species by cuttings in summer.
Opuntia (Prickly Pear, Indian Fig). Cacteæ.
Seeds grow readily, sown as soon as ripe in ordinary sandy soil, either in the house or out-doors. The joints grow readily if laid on sand. It is customary to allow these cuttings to dry several days before planting them. See also [Cactus].
Orach (Atriplex hortensis). Chenopodiaceæ.
Seeds, sown where the plants are to stand.