Orchid Roots

by Adam Dogwood

Plants within the genus Cattleya and related genera produce some of the most extensive root systems of any orchids. Their roots are thick and fleshy, and it is not unusual for a specimen to produce So per cent ofits root system outside the pot. Roots like this can be fed to great advantage. This plant can be repotted and the roots trimmed to about 6 in (15 cm), or left outside the pot.

Only occasionally is a single old leaf shed, their lifespan being for many years. The plant grows from a downward-creeping rhizome and the large green flower emerges from inside the base of the leaf. In cultivation the pendent habit should be retained and regular spraying essential.

All orchids produce roots. There are basically two kinds: aerial and underground. The root structure of orchids is peculiar to them, and all their roots are of a uniform thickness which does not increase with age. The roots will branch, in some species freely. All consist of a central wiry thread which is surrounded by the fleshy, moisture- retaining, part which in turn is coated by the white papery covering, the velamen, which grows as the root extends, leaving only the green growing tip exposed.

Monopodial orchids which grow tall, such as vandal, produce aerial roots from along the rhizome, from a node on the opposite side of a leaf. Here only one root is made and this will extend, rarely branching, for a considerable length. Usually one or two roots will be made each year.

In cultivation these roots can he aerial or underground depending upon the angle at which they are produced. Some may grow horizontally and remain as aerial roots until they come into contact with compost when they will grow into it to become terrestrial.

Roots made directly underneath the new growth will immediately penetrate the compost and either remain there or emerge from the pot at some stage and revert to being aerial roots. If artificially repotted, however, they will immediately suffocate and die, as will underground roots which are suddenly exposed to the air. One type can become the other by growing naturally, but both can be killed by a grower’ interference.

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