These Need a Warm Greenhouse for Their Successful Cultivation
(Dendro'bium). A large and popular group of greenhouse Orchids found wild throughout the East, in Ceylon, Burma, India, Australia, the Philippines, and in parts of China and Japan. Each kind has more or less adapted itself to its own special climatic conditions, with the result that the plants vary greatly in growth. Some are small and bear very small flowers; others have large pseudobulbs 4 or 5 ft. long. A few grow on rocks, but the majority are epiphytal, and have evergreen leaves. The name Dendrobium is derived from dendron, a tree, and bios, life, referring to the fact that the greater number grow on trees.
Dendrobiums are grouped in three sections: those which produce their flowers from the nodes of the stem in twos and threes, as in the popular D. nobile; those which produce their flowers in arching spikes from near the top of the cylindrical pseudobulbs, as D. Phalaenopsis; and others which produce large, handsome cones of flowers from near the top of large, club-shaped pseudobulbs, as in D. thyrsiflorum.
Summer and Winter Management. As Dendrobiums are so widely distributed, and vary so greatly, conditions of cultivation must necessarily be varied. They need warm, moist conditions during active growth, but the winter temperature must be regulated according to their needs. With care many of the Indian and Burmese kinds can be wintered in a temperature of 50-55 degrees. The night temperature for Australian, New Guinea and Malayan kinds should not fall below 60 degrees and 65 degrees is preferable. Though their pseudobulbs are much harder and apparently more resistant than those of many of the Dendrobiums from the Near East, they must not be rested completely, but must be watered at infrequent intervals even when not making fresh growth.
The Indian and Burmese kinds require abundance of heat, atmospheric moisture and water when in full growth; they must be shaded in summer, but need exposure to light and air in autumn to mature the growths. Those with hard pseudobulbs must have a definite rest, those with softer stems, such as D. infundibulum, must be kept moderately moist at the root throughout the winter, and others of intermediate character, like D. nobile, only need occasional watering at that season. The Australian kinds need much less shading through the summer, only sufficient to prevent the leaves from being scorched.
Suitable Potting Compost. The compost for all kinds may consist of finely cut osmunda fiber or of Fir bark. When repotting Dendrobiums as small a pot or pan as possible must be used, for the water must pass quickly away, and the compost must never become sodden. The smaller-growing plants may be placed in pans and suspended near the glass. Drooping kinds are grown in baskets, or sometimes on blocks of wood. Potting should be done in February or March, if possible, but only when the plants show signs of fresh growth; it must never be done in the autumn.
Propagation. To increase the stock, large plants are divided at repotting time, or, in the case of D. nobile and its hybrids and a few other kinds, matured and sound pseudobulbs may be cut into lengths of 2 or 3 in. Each of the pieces must contain one or two nodes. They should be pressed firmly on sand and laid in a propagating case with bottom heat in January. When new growths appear they may be taken off when rooted and potted separately.
Many Dendrobiums form young growths from some part, usually the upper portion, of the pseudobulbs; when rooted, these may be removed and potted. Such small plants should have the benefit of a propagating case, if available, for a time; or a warm position in the Orchid greenhouse.
Over a hundred kinds, in addition to numerous hybrids obtained chiefly from D. nobile, are known in cultivation, but the following are the most noteworthy.
The Favorite Dendrobium nobile, which has stemlike pseudobulbs, is 1-2 ft. high, and produces its flowers in twos and threes, in February and March, from the nodes of the previous year's pseudobulbs. The flowers are comparatively large, white, tipped rose-purple. D. heterocarpum has shorter pseudobulbs and yellow, fragrant flowers, in March. D. chrysanthum has long, slender pseudobulbs with deep orange-yellow flowers borne on the new growths, in summer and sometimes in autumn. D. crystallinum has erect pseudobulbs and white, magenta-tipped flowers in May or June. Other kinds which bear flowers from the nodes on the stemlike pseudobulbs are D. Aphrodite, D. Bensoniae, D. regium, D. Findlayanum and D. Wardianum.
Dendrobiums with conelike inflorescences are D. thyrsiflorum in which the bulbs are sometimes 30 in. high; the flowers are most striking. They have white sepals and petals and a golden‑orange lip. D. densiflorum is similar in habit of growth, but has golden-yellow flowers, and D. Farmeri, which is smaller, has straw-yellow, pink-tinted flowers. All flower in May, from the upper parts of old and new pseudobulbs. All the foregoing should be rested in winter, and need a minimum temperature of 50-55 degrees.
Flowers of Many Colors. Dendrobium Jamesianum and D. infundibulum have slender, erect stems, and bear large, white, orange-throated flowers in April and May. They should be kept moist throughout the year. Some botanists consider D. Jamesianum to be a variety of D. infundibulum.
D. fimbriatum has tall, stemlike pseudobulbs and bears orange-colored flowers in arching racemes; the variety oculatum has a dark blotch on the lip. Both flower in spring chiefly. D. Brymerianum has stems 12-14 in. high, with golden-yellow flowers, usually in May. D. clavatum and D. Gibsonii have tall stems and yellow flowers. For these kinds the temperature should not fall below 55 degrees in winter.
D. pulchellum (Dalhousieanum) has stout stems 4-5 ft. high and flowers 4-5 in. across, tawny-yellow, shaded with rose, and with two black-crimson blotches on the lip; the plant flowers about May and must have a tropical atmosphere, with a winter temperature of not less than 60 degrees. D. Phalaenopsis, a handsome kind from New Guinea, has stout pseudobulbs, 2-3ft. high, with fiveto twenty-flowered arching spikes. The large flowers of the typical kind are deep rose shading to purple, but great variation exists. Variety Schroederlanum is white. September and October yield the greatest crop of flowers, but they appear at all seasons. The winter temperature should be from 60-65 degrees at night. D. Victoriae-Reginae has clustered flowers of purplish blue; it needs a minimum winter temperature of 55 degrees.