When it comes to orchid potting soil, some growers do not believe in watering until the new roots are well established; others let the repotted plant go unwatered only a few days or, at most, a week.

There is no object in watering until the roots are at least formed because until then the plant cannot use water.

A light, daily overhead spray will be sufficient to keep the leaves green and bulbs plump until the roots do form, which may take as long as three weeks.

Labels are very important and should not be lost or placed on the wrong pot when repotting. Many types are available but only those that are water-resistant are satisfactory. White or colored labels of celluloid, dull on one side for printing with a lead pencil or India ink, are ideal.

When it comes to orchid potting soil, the potting method described applies to all Cattleyas, hybrids, and allied genera. Vandas, with their air-loving roots, must have different treatment.

Vanda coerulea, especially, will do better on a raft than in a pot. The roots will then be able to wander freely through the Osmunda tied around the base of the plant and the stocky aerial roots will break above the Osmunda.

One method of dividing a Vanda (not particularly recommended to the amateur, until he has at least gained some experience) is to cut off the top part of the plant below one or two of the big fat roots breaking from the stem.

The top part may then be tied on a raft, and both parts are supposed to grow and flower. This would be dangerous treatment for V. Sanderiana, a plant apparently loath to send out typical roots from the stem.

If Vandas are planted in pots, good drainage must be assured (at least one-third crock being used), and the plant should be well centered in the pot. Vanda Sanderiana, as has been indicated, is the most temperamental of the Vandas.

It thrives in a large pot and reacts badly to repotting. Old medium may be removed from the roots and fresh material tucked in its place. Repotting, with Vandas as with Cattleyas, makes a good time to check up on scale—a pest most detrimental to this plant.

Phalaenopsis give trouble to some growers. When potting, the plants should be well centered in the pot or basket. Medium or orchid potting soil, should be well packed but not so firmly as for Cattleyas.

Compost should come well up around the base of the plant, since Phalaenopsis has a tendency to force the constantly forming crowns up from the medium. There should be very good drainage.

Osmunda makes a most satisfactory medium. Phalaenopsis are heavy feeders and will usually exhaust the medium in two years, after which they should be repotted.

This orchid has strap-like roots that wander out of the container and become fastened to it, the bench, or adjacent pots.

These roots must be severed in repotting, and the plant is inevitably set back. The intense interest in gravel culture, which is spectacularly successful with Phalaenopsis, is partly a result of this difficulty in repotting.

Dendrobiums need to be repotted immediately after flowering since they start new growth almost at once. Osmunda agrees with them, although the addition of sphagnum is often helpful. The deciduous canes may be cut from D. nobile and D. superhum and laid on the gravel under the benches. They will break at the eyes and form new plantlets.

Dendrobiums may be accommodated in a variety of containers, but, since they thrive in confinement, the receptacle should be as small as possible. Rafts or baskets are suitable for the drooping types.

Drooping canes should be allowed to follow their inclination unless room is scarce, in which case they may be tied up. Other types will do well in pots with Osmunda as medium. Sanders recommends a compost of three parts finely cut Osmunda to one part of sphagnum.

Coelogynes, with few exceptions, should be potted in shallow containers in firmly packed Osmunda. When repotting, the growths should be placed toward the center and the compost mounded.

As they do not react well to repotting, it should be avoided when possible. Rather than repot, some growers prefer to add fresh orchid potting soil at the front of the plant.

From time to time freshly sifted Osmunda may be sprinkled over the top and watered in. Here again Sanders recommends a compost of slightly less than three parts Osmunda and a little over one part sphagnum.

Oncidiums, like Dendrobiums, do well in confinement. Their containers, which may be baskets or rafts, should be just large enough and, as a rule, hung in the light. Osmunda is a satisfactory medium.

When Oncidiums are potted in a basket there should be a great deal of crock and not much compost. Sphagnum may be added to the orchid soil or medium. The genus requires a lot of water and consequently adequate drainage.

A book might well be devoted solely to Cymbidiums. Every grower has his favorite mix of compost and these splendid plants do gratifyingly well in all mixes.

They are terrestrials and so do well in straight soil, although they seem to do best on a rich, well-drained medium. Old, clean Osmunda, collected when un-potting Cattleyas and other species, is excellent for this purpose.

A formula highly recommended by a successful grower is three parts of leaf mold (oak and sycamore), one part disintegrated granite, one-half part fibrous peat, and one-half part turf and sand.

One grower's wife has been heard to complain that her husband tears up the front lawn to get potting material for his Cymbidiums. The use of fertilizer is a controversial matter, but it is probably good for these heavy feeders. Addition of leaf mold is always recommended.

Cymbidiums need moisture at the roots at all times and correspondingly good drainage. Since these plants grow enormous bulbs, a large pot is necessary.

The time for repotting is late spring when new growths are just beginning. Backbulbs may be removed without disturbing the plant and they will start new plants from the dormant eyes.

When potted the backbulbs should be centered in the pot since there is no way of predicting the direction in which the eye will break. They should be potted firmly, although not so tightly as Cattleyas, and they may be held fast with a stake.

Cypripediums have needs very similar to the Cymbidiums, but require more water and not such firm potting. Cypripedium roots are brittle and delicate and should be handled gently to avoid injury.

If the plant is soaked for several hours before being removed from the pot, the compost may easily be separated from the roots.

When it comes to orchid potting soil, Cypripediums can be readily divided during repotting, as they practically fall into separate plants, but, lacking pseudo-bulbs, they take up little room and there is not much need for separation.

Pots of four to six inches will be most convenient to handle. The plant should be well centered since new growth may break from any side.

This genus will do well with the composts used for Cymbidiums. The native habitat of the Cypripedium is usually swampy, so they need a rich, wet compost or orchid potting soil.

One grower recommends a mix of almost liquid, mud-like leaf mold to be poured around the roots and kept wet. Osmunda, preferably partially decomposed, is effective.

A satisfactory formula for the green-leaved types is three parts loam, one part of Osmunda chopped fine, and one part sphagnum. The mottled-leaved varieties do better with a formula of one part loam to two parts of Osmunda and two parts of sphagnum.

Odontoglossums also require a rich, moist compost; they thrive in leaf mold and heavy soil. Osmunda tends to be too dry. Old Osmunda, the residue from previous repotting of other orchids, can be used in repotting Odontoglossums, and a bit of sand may be added. Polypodium mixed with finely chopped Osmunda is also used.

A more elaborate mix consists of sphagnum, fine-cut fiber, a little sharp silver sand, and a few decayed oak leaves. These plants do exceedingly well under oak trees in localities where they can be grown outdoors.

As Odontoglossum roots are very fine, the plants should be soaked before repotting so that the old material will fall away without injuring them. About two thirds of the pot should be filled with crock to insure good drainage. Odontoglossums should be potted firmly but not tight.

Water should be withheld until new roots form, and then frequent damping will see the plant through in good shape. This genus does not react well to disturbance of the roots during hot weather, so September is the ideal time for repotting; growths will then be about an inch high and the plant will have a chance to re-establish itself before winter.

Repotting is also possible in March as new roots will have a chance to form before hot weather sets in.

Miltonias may be repotted at the same time as Odontoglossums. Straight Osmunda may be used. Another medium consists of equal amounts of peat and moss, with good drainage. Pots, not too large, are used as containers. Extreme care should be taken that repotted Miltonias do not receive water until new roots form.

When the first orchids were imported from their native jungles many years ago, thousands of plants died from being transferred to unnatural conditions under glass with the aerial roots crammed into unsuitable media.

Gradually but surely painful experience has evolved the modern treatment that is now so successful that hothouse-grown plants often far surpass jungle plants of the same species in beauty, and in number and size of blooms.

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