Feeding Orchid

When it comes to feeding orchid, they are divided into groups defined largely by the method of securing food. The two major groupings are terrestrial and epiphytic.

There are sub-divisions into semi-terrestrial and semi-epiphytic, but in a consideration of feeding we need be concerned only with the major groupings.

The terrestrial group, as the name indicates, grow in soil. Many North American orchids are found in shadowy, marshy, rich ground or in springy mountain meadows near streams. Cypripe-diums, Spiranthes, and Habenaria are among this group.

They are exquisite even when tiny, but resist all efforts to domesticate them. Tropical Cypripediums are also terrestrial but are successfully grown under greenhouse conditions.

Cymbidiums, native to many areas of the Far East, make up a large and valuable portion of the terrestrial group.

They are often found on trees or logs, a position that really classifies them as semi-terrestrial.

Wherever found, they send out long, searching roots into the leaf mold at the base of the tree or under the log. When fed richly, their heavy, round, corky roots attain great size and length.

The soil in which they thrive varies exceedingly and it is comparatively easy to satisfy them under cultivation. Growers who disagree on all other points of culture see eye-to-eye on the advisability of supplementary feeding of Cymbidiums.

The epiphytic group includes Cattleyas, Phalaenopsis, Vandas, Dendrobiums, Laelias, and Oncidiums. Large numbers of epiphytic orchids, which obtain sustenance from chemicals in the moisture of the air, are found perched like nesting birds in the crotches of jungle trees.

They usually send out two types of roots: one flat and straplike, that wind around the host for support and cling so tightly that they must be broken to release the hold; and the other, more flexible, that dangle in the air or penetrate the accumulated debris of dust, rotting leaves, and bird lime in the tree crotch.

Frequent tropical rains slowly release available food materials and frequent drying winds aerate the roots and prevent any unhealthy chemical development.

Plentiful sunshine steps up the process of photosynthesis and the orchid thrives until the dry months bring an enforced rest period.

Not all epiphytic orchids are good subjects for supplementary-feeding orchid experiments. Cattleyas grow so well in greenhouses on a simple diet of Osmunda and Polypodium that, as long as they are properly repotted every two or three years, any need of extra nourishment is unlikely.

Phalaenopsis, on the other hand, grow and bloom so prolifically that they soon exhaust their food supply. Since they do not respond well to repotting, there is a real need for artificial feeding.

The slowness of orchid growth, the long periods of plant in¬activity, and the difficulty of raising orchids from seed long ago led growers to experiment with artificial feeding orchid.

The results were often confusing and, more frequently, discouraging. There were hopes that the growth rate could be speeded up, the rest period dispensed with, and the production of flowers increased if a proper

adjustment between minerals, moisture, aeration, and light could be worked out. Although if some of the wilder hopes have been dimmed, there is still reason to believe that much can be accomplished.

The peculiar roots of the orchid permit absorption when food and moisture are available, and prohibit an excess of transpiration during drought.

The adjustment of artificial orchid feeding to these roots seems to be a problem for the scientist with a knowledge of chemistry and a feeling for growing plants. But amateurs have successfully invaded the field.

They have shown that one of the most important factors of artificial orchid feeding is an intelligent application of conclusions drawn from close observation of the effects of such feeding.

Some of these conclusions are that a plant that has plenty of light but whose leaves remain yellow probably needs iron; that too much nitrogen produces a beautiful green growth but may slow down flower production; and that precipitation of chemicals in the medium will injure the plant after a short period of well-being.

As has been shown, the feeding of terrestrial orchids is not complicated. Orchid Food may simply be added to the potting material as needed.

Foods commonly used are bone meal, blood meal, leaf mold, rat's nest, manure (well-rotted and carefully used to prevent burning), and any of the nutrient formulas (such as Knudson's 'B' or 'C') or the commercial preparations specifically recommended for orchids.

Artificial feeding orchid of epiphytes is a much more complex problem. After first being discouraged by the great casualty rate among tropical orchids that were treated like earth plants, early growers hit upon the very successful method of potting them in Polypodium, Osmunda, tree fern, or English peat. It is doubtful if they knew why these media were good.

The alternate watering and drying out of the potting material released the stored food and dried out the roots, preventing rotting. In other words, the roots were aerated and could breathe. The conditions of their native habitat were sufficiently approximated.

As it is the nature of man never to be satisfied, however, growers still felt that supplementary feeding might accelerate growth and flower production, but found in the experiment that Osmunda and Polypodium are no longer ideal media.

They break down rapidly and become sour. Roots begin to rot and the plant suffers. Eventually there is a concentration of chemicals, which even frequent flushings with clear water will not wash away.

The very special technique of gravel or Haydite culture may be the answer to this problem of feeding epiphytes. Both are inert and form a good base for the roots that support the plant.

They have the added advantage of providing excellent drainage and aeration. Well-washed quartz gravel has been used in many sizes.

Many growers use large gravel at the bottom of the container with a layer of fine gravel on top to provide a better clinging surface for roots.

Haydite is a shaly deposit that has been subjected to heat at high pressure and has expanded and become porous. Both gravel and Haydite have their advocates.

No conclusive results have been published on gravel culture of adult Cattleyas. Growers who have experimented do not seem sure of the results and are inclined to hedge when asked about them. Many commercial growers have tried gravel with Cattleyas and then abandoned the idea.

It is not known whether this is because the plants did not thrive or because the practice did not bring results commensurate with the labor and expense involved. Cattleyas do so well in Osmunda that further experiment may be pointless.

More positive results have been noted with Cattleya seedings and Phalaenopsis. The latter, with their flat strap-like roots and spreading habit of growth, do particularly well in gravel or Haydite.

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