Impatiens Sultani.—Half-hardy perennials. May be raised from seed sown early in spring on a hotbed, or later on in a shady spot in the open border; greenhouse culture, however, is more suitable. They bloom in August. Height, 1½ ft.
Incarvilleas.—Ornamental hardy herbaceous plants, of easy culture. They are suitable for the border or the rockery, and will grow in any soil if not too dry and exposed. The tuberous roots may be planted at any time in autumn, 4 in. deep. I. Delavayi makes a fine solitary or lawn plant, its leaves being from 1 to 3 ft. long; the soft rose-pink, Mimulus-shaped flowers, which are carried on stout stems well above the foliage, appearing in May. Care should be taken not to disturb it in spring, and it is advisable to cover the roots in winter with a pyramid of ashes, which may be carefully removed at the end of April. Incarvilleas may be propagated by seed sown, as soon as it is ripe, in light, well-drained soil, giving the young plants protection in a frame during the first winter, with enough water merely to keep them moist. Height, 2 ft.
Indian Corn.—See "Zea."
Indian Shot.—See "Canna."
India-rubber Plants.—See "Ficus."
Indigofera.—Beautiful evergreen shrubs. I. Australis has elegant, fern-like foliage and racemes of pink or purple Pea-shaped flowers in April. I. Decora Alba bears its white flowers in July. They require a sandy loam or peat soil, and greenhouse culture. Cuttings of the young wood planted in sand under glass will strike. Height, 2½ ft.
Insects on Plants.—To destroy insects on plants wash the plant with Tobacco-Water (which see). Or put 1 oz. of quassia chips in a muslin bag, pour on some boiling water, and make it up to I gallon; dissolve 1 oz. of soft soap, add it to the chips, and stir well. Use it two or three times during spring and early summer.
Inula Royleana (Fleabane).—A hardy perennial which flowers in November. It will grow in any garden soil, and can be increased by seeds, or by division of the roots. Height, 3 ft.
Ionopsidium.—These hardy annuals grow freely in any rich, damp soil; a shady position is indispensable. Height, 1/8 ft.
Ipomoea.—These beautiful climbing plants are very suitable for covering trellis-work, or for the pillars or rafters of the stove-house. The seed is generally sown in April on a hotbed or under glass, and the young plants set out in the border of the house in May in light, rich soil. Success is mainly secured by allowing plenty of root-room. The perennial kinds are increased from cuttings taken from the small side-shoots placed in sand in a brisk bottom-heat. If grown in the open they often shed their seed, and come up year after year with but little attention. They make a good contrast to Canariensis. The Ipomoea Horsfalliae, with its bright scarlet flowers, has a lovely appearance, but must be treated as a stove evergreen. This is propagated by layers, or by grafting on some strong-growing kind. It thrives in loam and peat mixed with a little dung, and flowers in July or August. Height, 6 ft. to 10 ft.