POTTING MATERIAL FOR HYBRID ORCHIDS
From the time the little plants are well established in single pots, the same potting material used for all of their kind may be employed, the plants in the earlier stage having the potting material in a finer condition than that provided for the larger plants as they approach the flowering stage.
As with other important operations, in Orchid potting and in the material used the practice varies considerably, even in the best collections, and this points to the fact that if the accommodation is good, the houses properly heated, and other details of culture carefully carried out, the exact composition of the potting material is of minor importance. For Cattleya and Lælia hybrids and a large number of epiphytes grown with them the compost is made by tearing up the materials with the hand, or in some other way which will not break the fibres very much. Osmunda fibre forms one-half to two-thirds of the compost, the other third being made up of good Sphagnum-moss and Oak leaves or other decayed, dryish leaves. We do not recommend leaf-soil or leaf-mould, which was formerly strongly advocated, especially by Continental growers, who used it with disastrous results. The most that is done now is to mix a proportion of it with other potting material for Lycastes, Calanthes, Phaius, and similar strong-growing terrestrial Orchids.
For mixing with the compost for hybrid Orchids, some use crushed crocks, sand, charcoal, and a small proportion of each or either may be employed safely, although there is no real need for such materials.
Polypodium fibre may also be substituted for Osmunda fibre, or a proportion of each may be used. Orchid peat fibre, which used to be the chief potting material for Orchids, is still perhaps as good as any of the other fibres, provided a really good quality can be obtained, a matter which has become increasingly difficult.
For Cypripediums, and especially Selenipediums, a proportion of good, fibrous loam should be added to the compost recommended for epiphytal Orchids, the proportion of loam being increased as the plants get larger. Phaius, Calanthes, Zygopetalums, Zygocolax, and other plants of a similar character should also have a proportion of loam-fibre in the compost, and in these cases Orchid peat may be substituted for Osmunda fibre, if it is of good quality. So far as it has been tested, Osmunda fibre has an advantage over other fibres, in that it is more durable, retaining its fibre intact longer than any other. Osmunda fibre and Polypodium fibre in equal proportions, with an addition of leaves and Sphagnum-moss, make an excellent material for all young, epiphytal Orchids, the finer Polypodium fibre, if well worked in, giving substance to the more open Osmunda fibre.
For very small plants it is well to rub the mixture through a coarse sieve, but after the early stages the use of the sieve should be discontinued, and the compost carefully mixed with the hands.