Page:The Amateur's Greenhouse and Conservatory.djvu/240

222 the block, and after placing a thin layer of moss over them, secure the plant to the block with copper wire. Cattleya citrina should always be grown on a block, with its leaves hanging downwards, because in its native habitats it always grows on the underside of the branches of trees. Terrestrial species must have good drainage, but they do not require potting so high as advised for the others. The best time for potting, or dividing the plants, is just as they start into growth.

The temperature should range from 55° to 75° from March to October, and from November to the end of February an average temperature of 10° lower than that advised for summer will be the most suitable. The atmosphere must be kept rather dry through the winter months, as the plants will then be at rest, but during the season of growth it must be kept constantly moist by frequently sprinkling the walls and floors; and in very hot weather a slight sprinkle overhead in the afternoon, when shutting up, will be of great service. Syringing the plants must, however, be done very carefully, or much harm will result. There is no fixed rule with regard to the application of water to the roots, and it may be taken for granted that when the plants are growing freely, a fresh supply will be required as soon as the soil begins to feel rather dry. If they are watered constantly, whether they require it or not, the roots will soon rot and the plants perish. Those growing on blocks must be dipped in a pail of tepid water every other day during the summer, but in the winter once in three weeks will be quite sufficient. Pot specimens, when at rest, only require enough moisture to prevent the leaves and pseudo-bulbs from shrivelling.

Shade sufficiently to prevent the sun scorching the foliage, but at the same time admit all the light possible to promote a robust growth. This is especially necessary after the middle of August to promote the perfect ripening of the growth of the summer, for if this is not well matured before winter it is impossible for the plants to flower satisfactorily or remain in good health for any length of time. Orchids require very little air in proportion to many other classes of plants, but the house must be ventilated sufficiently to maintain a pure atmosphere. In the winter scarcely any ventilation will be required, and the air must only be admitted in calm and genial weather.