This huge genus (it may include as many as 1,400 species and even more hybrids) ranges from Japan and the Himalayas to Australia and the Pacific islands. Many are grown by orchid fanciers in greenhouses (outdoors in southern Florida). Some have thin, canelike pseudobulbs, others short, fat ones. Only a few of the more widely grown are mentioned here.
Culturally, dendrobiums fall into two classes. Intermediate-climate types are evergreen; they need water throughout the year (somewhat less in winter) and temperatures similar to those required by cattleya orchids. Cool growers drop some or all of their leaves during a period of winter dormancy, at which time they need very little water (only enough to keep pseudobulbs from shrinking) and temperatures suitable for green-leafed paphiopedilums.
D. bigibbum phalaenopsis (D. phalaenopsis). Intermediate grower. Native to Australia, New Guinea. Blooms throughout the year, with canes up to 3 ft. tall producing arching spikes that carry as many as ten 3-in. purple flowers. The parent of many hybrids.
D. hybrids. A bewildering number of hybrids have been produced in Hawaii and elsewhere, both for ornamental pot plants and for cut flowers and leis. Most are intermediate growers. Buy plants in bloom to get desired flower color and bloom season.
D. kingianum. Cool grower. Native to Australia. Makes large clumps of 2- to 20-in. pseudobulbs topped by 4-in. leaves. In late winter or early spring, erect spikes to 8 in. long carry a few or up to as many as 20 fragrant, inch-wide flowers in pink, white, or red.
D. nobile. Cool grower. Himalayan native. Canes 1220 in. tall carry two ranks of 2- to 3-in. leaves; leaves last for about 2 years. Short inflorescences on leafy and leafless canes carry two to four fragrant, 1-in., white- to-purplish pink flowers with a yellow or white zone around a dark purple eye. Blooms almost any time of year. The parent of many colorful hybrids.
D. speciosum. Cool grower. From Australia. Large masses of pseudobulbs (ranging in height from 4 in.3 ft.) are topped with leaves that are 110 in. long. Blooms in late winter or early spring. Inflorescences are crowded spikes of fragrant, creamy-to-yellow flowers; they resemble bushy foxtails, can reach 22 ft. long.
Indoors, dendrobiums need at least 6 hours of good sunlight per day; place them directly in front of a southern window. During active growth and bloom, they need high humidity and frequent watering. Feed monthly with water-soluble 30-10-10 fertilizer. Easier to bloom in a greenhouse than a home.