Degrees Fahrenheit. The higher day temperature should be obtained by sun-heat when possible.
Further remarks on this and other details will be found under the headings of the different genera, but it will be better now to state in general terms that during the season of active growth any reasonably high temperature by sun-heat, secured by keeping the house tolerably close and well shaded, greatly benefits the plants. This is specially noticeable where batches of Dendrobium nobile, D. Wardianum, and other deciduous Dendrobiums are grown. Those who grow them best allow the house containing the plants to become very warm; they remove the shading early in the afternoon in order to let the plants get the longest duration of light possible, and they keep the house very moist until the evening.
THE SINGLE ORCHID HOUSE
It is doubtful whether the owner of a large collection of Orchids gets a greater amount of pleasure than the beginner starting with but one Orchid house, provided the owner of the single structure is careful in selecting his plants.
In cases where only one Orchid house is possible, and a more or less general collection of plants is desired, that house should be heated as an intermediate house. The single Orchid house has often been the starting-point of more extensive culture. It is generally commenced by utilising an existing plant-house, in some cases, unfortunately, without making the necessary preparation for the new occupants.
When it has been decided to adapt a house for Orchids, the proper course is to clear the house of its contents, thoroughly overhaul the interior fittings, such as staging, &c., and make any alterations necessary. The heating apparatus should be regulated, and, above all, the best possible provision must be made for catching and storing rain-water, even if this necessitates the providing of a brick and cement tank beneath the staging.
If the existing floor in the house is of concrete or tiles, or any similar material, it must be removed, leaving the natural earth for the surface of the basement, and providing a wood-trellis for walking on in spaces between the stages. Let the house be thoroughly cleansed and painted, and after a short time has elapsed it will be ready to receive the plants.
In such a house heated as a cool, intermediate house, with a minimum temperature of 50° to 60° Fahr. in winter, a large number of showy Orchids can be grown successfully. Those species which require great heat should be carefully avoided, for, although cool-house Orchids are easily managed in a house warmer than is necessary for them, the hot-house kinds usually fail in a temperature which is too low to allow of their making growth under favourable conditions. In such an intermediate house the Odontoglossums, Masdevallias and other favourite cool-house Orchids can be grown successfully, if arranged in the cooler part of the house and carefully watered. The Cattleyas, Lælias, and the garden hybrids should be placed on the staging in the middle of the house, well up to the light; the Brazilian Oncidiums, Sophronitis grandiflora, and Stanhopeas should be suspended from the roof of the house, but in such positions as will avoid placing them over the plants on the side staging. The Odontoglossums and Cochliodas may be accommodated on the side staging in the cooler and moister part of the house. In such a house all the varieties of Cypripedium insigne, C. Spicerianum, C. Charlesworthii, and all the green-leafed section known as Selenipediums, will thrive admirably, and a very large selection of other showy Orchids, including Zygopetalums; but again I would say that species which are usually regarded as warm-house Orchids must be rejected.
SHADING
It should be distinctly understood that every Orchid house needs to be fitted with proper means of shading, extending over the whole roof and removable when necessary. Some cultivators think they meet the case by providing shading only on the sunny side, or by painting the glass with some kind of preparation more or less in the nature of whitewash. Such preparations should never be used, because, when this is once placed on the glass, the shade, such as it is, is there in dull as well as bright weather, in the night time as well as the day, and for the greater part of the time, especially in dull seasons, it obstructs light which is necessary for the proper development of the plants. Another important objection to their use is that shading given by these washes wears off and leaves the plants exposed to the full sunlight. The substance is washed off by the rains and carried into the rain-water tanks, thus causing injuries to the plants watered with the polluted water, and rendering unsightly the foliage moistened with it.