Planting & Propagation of Orchids

For many years, orchids were considered to be a greenhouse plant. But there are many varieties which, when given appropriate conditions and care will do quite well in a home environment. Some varieties may be difficult to grow, and therefore best left to greenhouse culture. Most cool-growing orchids will not thrive in hot, tropical conditions because they come from the world's mountainous regions, which are often shrouded in mist and clouds. The plants will not thrive and their flowers will wilt and fall within days, if they are grown in such conditions.

Cultural Requirements

Orchids are different from other houseplants. Most orchids in the wild are not rooted in the ground, but instead attach themselves by thick roots to the sides of trees and on branches. Clinging to the bark, the plants absorb water and nutrients from the air and rain and whatever drips down the tree. They are adapted to surviving when rain is scarce, hoarding water in thick leaves, stems and roots.

In the house, orchids are grown in pots filled with chips of bark, stones, treefern, charcoal pieces or some other loosely packed material, which keeps roots well-aerated and permits water to drain quickly.

The most commonly used method of propagating orchids is through division. This is one of the simplest methods of producing more plants of the same variety or species. Division simply means splitting the plant into two or more parts each with at least one new shoot and each will produce a fully grown mostly flowering size plant that is capable of flowering the following season. Splitting a plant will encourage the plant to produce more shoots of a better quality. Only divide plants where each division will have at least three back bulbs and each division should have at least one new growth.

Back bulb propagation is a method of producing a new plant from old previously flowered or unflowered back pseudobulbs which are usually leafless. This is also a simple method of propagation but this one may take many years to obtain a flowering size plant. The process involves the removal of older back bulbs (old growth) - preferably at re potting time - and placing them under suitable growing conditions to induce rooting.

Orchids are generally difficult to grow from seed, because in nature they require a symbiotic fungus.

Orchids can tolerate a pH from about 5.0 to about 8.5. Seedlings have been grown on many different media, and the best medium varies between species. All the media used contain a carbohydrate source, a range of mineral salts and agar, and many also contain vitamins, amino acids, growth regulators or plant extracts such as banana pulp or potato extract. The media are sterilised in an autoclave. The main culture room conditions are a 16 hour photoperiod and a temperature range of 22-25°C. Some seeds are germinated in the dark or in low light.

The developing seedlings need to be sub cultured several times until they are large enough to be transferred to the glasshouse. Well grown seedlings are removed from the flasks and established in the glasshouse environment. This process is known as 'weaning' and care has to be taken to ensure that the seedlings suffer as little stress as possible until they have hardened off, as the leaf cuticle is often poorly developed in 'in vitro' culture. They are potted in either an epiphytic or a tropical terrestrial seedling compost as appropriate.

Sympodial orchids ( new growth appearing from the base of an older growth) can be propagated through division. Cut through the rhizome leaving ideally at least three growths on each portion, this can be done at any time, providing the plant remains undisturbed in its original compost until the next re-potting takes place, when you should have perfect divisions.

The propagation of monopodial orchid is slightly complicated. When the plant has reached a size too big to cope with, it may be cut down, providing that there are sufficient aerial roots on the cutting to make it viable, which can then be re basketed to grow on, the old stump should not be thrown away, as it may well produce several new growths from below the cut, and these may be eventually removed to form new plants or left as a splendid clump.