Orchids

Orchids have been called the aristocrats of flowers, but perhaps it would be better to liken them to queens. Once admired mainly in prom or opening night corsages and as exotic displays in conservatories or botanical gardens, the orchid has now descended from her throne and is to be found in florist shops, nurseries, and even on the racks of discount stores and supermarkets. Orchid societies hold shows and sales in shopping malls, and many other venues, where it is possible to find a flowering plant for no more than you would pay for an azalea. Familiarity in this case, however, breeds not contempt but attempt, as new converts discover how surprisingly easy it is to grow orchids.
The most familiar orchids are phalaenopsis, cattleyas, cymbidiums, and paphiopedilums (lady's slipper orchids), but other kinds - notably dendrobiums, miltonias, and masdevallias - are gaining in popularity. In addition, there are countless others to lend variety to a collection.

The thousands of species of orchids make up an exceedingly varied family. Many orchids are so different in appearance that it's hard to believe they are related. Even given their amazing variety of sizes, shapes, and proportion of parts, orchids do have a number of mutual characteristics that distinguish them from other plants.

Botanically speaking, orchids are perennial plants with zygomorphic, or irregular, flowers (that is, they can be divided into two equal halves in only one plane - unlike, say, a rose or camellia flower, which can be divided in any of many planes). Flowers typically consist of three outer segments (sepals) and three inner segments (petals), one of which is greatly modified in form and called the labellurn, or lip.

The reproductive parts of the flower are concentrated in an organ known as the column. The purpose of the many highly complex structures involving the lip and column is to ensure that the pollenizing agents (bees, flies, beetles, birds) will transfer pollen from one flower to another of the same species, preventing either self-pollination or cross-species pollination.

Many modifications of the flower structure occur: the lip may be enormously enlarged or reduced, the petals may be so reduced as to become nearly invisible, and one or more of the floral parts may be fused or drawn out into long tails. These irregularities and the complex structure of the orchid flower give it a strange beauty-and, not surprisingly, other strangely beautiful flowers are often mistaken for orchids.

Orchid flowers come in all colors except true black (and Coelogyne pandurata has markings that approach true black), but the predominant colors are pink, lavender, red, yellow, and white. True blue is rare and much esteemed; brown and green are quite common, and many species have flowers marked with two or more contrasting colors. The highly fragrant zygopetalums commonly have green-and-brown sepals and petals, with a white lip marked in purple.

Flowers vary in size from nearly a foot across to mere pinheads. Many have fragrances ranging from fresh and fruity to sultry and exotic.

Orchids' growth habits are nearly as varied as their flowers. Many grow on trees (epiphytes) or rocks (lithophytes), surviving on rain and the nutrients brought them by decaying leaves and other organic detritus. None is a parasite; orchids may live on a tree, but they take no nourishment from it.

Others (terrestrials) live in the soil and may have fibrous roots, rhizomes, or tubers. A few (though not in cultivation) have no chlorophyll and live as saprophytes on decaying plant matter in the soil. Some familiar orchids are opportunists, sometimes living in pockets of leaf mold on rocks or in the crotches of trees, sometimes flourishing on the ground in rich, highly organic soil.

Two types of growth

Orchid plants increase their size in one of two ways. Those with monopodial growth become taller each year as a consequence of new growth forming only at the tip of the stem. Leaves are set in two rows on opposite sides of the stem, each one alternating with its partner. Flower spikes and aerial roots originate in a leaf joint or opposite a leaf. The stems may become tall, as in many species of Vanda, or may be so short as to be practically invisible, as in species of Phalaenopsis. Note that if these orchids' top growth becomes damaged, they may still produce new growth from dormant buds lower on the stem.

The second growth type, by far the more prevalent, is sympodial. Here the upward growth of the plant stops, in most cases, after one season; the next year's growth arises from the base of the prior year's, extending the plant laterally (or vertically, if the plant is growing on a vertical surface). Sympodial orchids may bloom from the tips of the most recent growth, from its base, or from buds on older growths.

Many sympodial orchids develop thickened stems called pseudo bulbs; these store water and food, enabling the plant to survive periods of drought. Pseudo bulbs may be round and fat, flattened, or elongated into cylindrical stems usually called canes. They vary from microscopic to many feet in length. Leaves may grow either along the pseudo bulbs or from their tips.

Where they grow

A few terrestrial orchids grow north of the Arctic Circle, but many more grow in the temperate regions of Europe, Asia, and North America. A large number of terrestrials grow where the, climate is "Mediterranean"- South Africa, the Mediterranean basin, Chile, and parts of Australia. Most of these tend to grow and flower in winter and spring, resting during the dry months as tubers.

In cold-winter regions terrestrials overwinter as dormant tubers or rhizomes, and then grow, flower, and set seed in spring and summer. In such areas of North America they are considered difficult to grow and are rarely seen as garden plants.

Epiphytic orchids are found chiefly in subtropical and tropical regions (although one, Epidendrum conopseum, grows as far north as North Carolina, and several Asiatic species range northward to Japan). Although often thought of as jungle plants, they are seldom found in dark, dank undergrowth. Most live on trees high above ground where light is plentiful, or on rocky ledges in clearings and at forest's edge. Many live where rainfall is seasonal, so have evolved mechanisms to conserve moisture.

A history of orchids Growing orchids Glossary Pests & diseases What kind of orchid is that

Africa and Australia have large numbers of epiphytes, but the tropical Americas, southeastern Asia, and the islands of Indonesia have many more. In all of these regions orchids grow from sea level to the timberline, from steaming coastal forests and seasonally dry scrub woodlands to perpetually moist mist forests at the higher altitudes. Probably the highest concentrations flourish in the mountains of New Guinea and in the misty mountains of Costa Rica, Colombia, Ecuador, and Peru. Obviously, one set of growing conditions will not suit all species.

Epiphytes and lithophytes have had to adapt to receiving irregular supplies of food and drink. Many of these are orchids with pseudo bulbs. Most also have thick and fleshy leaves, whose waxy surfaces evolved to retard the transpiration of water. Some drop their leaves during rest periods and await rains to resume growth.

The roots of epiphytic orchids are also well adapted for gathering and preserving moisture, being thick, little branched, and covered by a velvety or spongy layer known as the velamen. This layer is made up of many cells that when dry are filled with air, but that readily take up moisture from rain or atmospheric humidity and retain it for a long time.

In addition to extracting water and nutrients, the roots of epiphytic orchids can anchor the plants on their perches. These roots have the ability to fasten onto any available support, insinuating themselves into the crevices of tree bark or clinging tightly to porous ceramic pots.