Easy culture and a lavish show of long-lasting flowers have made cymbidiums favorites with gardeners and commercial cut-flower growers alike. Standard cymbidium hybrids produce multiple 3- to 4-foot flower spikes from February to early May (some as early as Christmas), and each spike may contain as many as thirty 4- to 5-inch flowers. The flowers have a heavy texture and last well on the orchid, for 8 weeks or perhaps more. As the cut flowers are similarly durable, cymbidiums rival cattleyas in popularity as corsages.
The orchids have tightly clustered egg-shaped pseudo bulbs clothed with the bases of the gracefully arching strap-shaped leaves. Unlike many orchids, cymbidiums are handsome plants even when out of flower. All are natives of a range from Japan and India to Australia. The large-flowering kinds are native to high, cool mountains and need cool nights to produce flowers. In warm-summer, cold-winter regions, grow them outside and bring them indoors before the first frost.
Smaller Chinese and Japanese species, grown in Asia as potted plants for centuries, are gradually gaining recognition elsewhere. A few dwarf species have been instrumental in producing miniatures and hybrids with hanging flower spikes. Some of these species are warm growers that can flower without the cool nights required by the large flowering kinds.
The aforementioned "easy culture" does need some qualification: for one thing, the large standard cymbidiums so popular as outdoor container plants on the Pacific Coast need low night temperatures to initiate flower buds. High daytime temperatures do not disturb them so long as they are not allowed to become sunburned, but nighttime temperatures should not exceed 60°F (16°C) in the fall.
Then too, from March to October, while new growth develops and matures, these orchids need frequent watering. After that their water supply may be reduced, but low night temperatures of about 45° to 55°F (7° to 13°C) remain necessary if the plants are to flower.
The plants themselves are hardy to 28°F (- 2°C), but their flower spikes are more tender and can be destroyed by frost. When low temperatures are predicted, move outdoor orchids beneath a deep overhang or into a garage or shed-or else cover them with cloth or plastic, making sure that the material does not touch your orchids.
Many potting mixtures are available for these terrestrial orchids. Most are based on fine-grade fir bark blended with moisture-retaining elements such as peat moss, leaf mold, or sponge rock; some incorporate fertilizers. The most important factors in any mix, though, are fast drainage yet good water retention. Pots should, of course, drain freely. Clay pots are satisfactory, but plastic pots with drainage holes on the bottom and sides are widely used because their weight doesn't add to that of the plants, which can become very large.
Cymbidiums should have enough light during the growing season to produce yellowish green foliage. If the foliage is dark green or bluish green, your light is inadequate, and your orchids may fail to flower satisfactorily. Where plants are hardy, grow them outdoors under lath or in light afternoon shade. Many people report successfully growing plants at the edge of east-facing porches, where they get full morning sun and modified light the rest of the day.
These orchids are heavy feeders: give them a complete liquid fertilizer every 2 weeks from January through July, cutting back to once a month from August through December. Slow release fertilizers will reduce your feeding chores; use them according to the package instruction.
Because cymbidiums flower best when their roots are crowded, transplanting is necessary only when the pseudo bulbs begin to crowd the edge of the pot. The best time to transplant is just after flowering. Remove the orchid from the old container; if it proves difficult to slip out, invert the container, hold it by its edges, and tap it firmly against a sturdy table, bench, or fence rail. Sift the old bark or mix out of the roots, cut off any dead roots, and trim back live roots to half their original length. If you wish to divide orchids at this time, cut through the rhizome with a stout knife or pruning shears, leaving at least three leaf-bearing pseudo bulbs in each division. Do not use a pot several sizes larger when transplanting; instead, select one that will allow no more than 2 or 3 inches between the leading edge of the plant and the side of the pot. Remember, you want to maintain those somewhat crowded conditions.
Add moistened bark or mix to the pot, tamp it down, and then hold the orchid in position with one hand while dropping mix down the sides with the other. Position the orchid to allow space for the leading edge, or growing point, and continue to add bark, tamping it firmly around the roots. Water lightly until new growth becomes evident; then resume watering and feeding on your regular schedule. Be sure to sterilize your tools before-and after-cutting any orchid tissue.
Leafless pseudo bulbs, or back bulbs, may be used to start new orchids. Each will have a small bud at its base. Stand this bulb upright when it develops visible growth. Then plant it in potting mix with the new growth at soil level. The bud will develop slowly into a foliage fan. With care, you will have another flowering plant in 2 or 3 years.
Those who find standard cymbidiums too large and too dependent on low temperatures can enjoy the miniatures-hybrids between the big standards and several smaller species, notably C. pumilum. These more petite versions are easy to bring into flower, highly floriferous, and of a reasonable size (1 1/2 to 2 feet tall) for home decoration or the small greenhouse. The flowers are smaller than those of standards, yet profuse, and come in the same color range as that of the standards: white, pink, red, bronze, brown, yellow, and green, usually with contrasting lips. They tend to flower earlier than the standards as well: some will flower as early as July. Many miniature cymbidiums were bred to tolerate warmth and will often fail to flower when grown out-of-doors in the conditions that suit standard cymbidiums. They will thrive, however, when given the same conditions that suit cattleyas. It is always wise to check the growing requirements of a specific miniature before purchasing it.
Dwarf cymbidium species
These, the orchids of classical Chinese and Japanese art, have been treasured house plants in Asia for 2,000 years.The plants are small with very tiny, sometimes subterranean, pseudo bulbs and gracefully arching, grass like foliage. The flower spikes are erect, and the small but characteristically orchid-shaped flowers are marvelously fragrant. Their popularity is now spreading from Asia to the worldwide orchid-growing community.