Water supplies under glass are often mishandled. The best water supply is rain water from the houses themselves, brought into a tank inside theso that it is always at approximately the same temperature as the soil of the . Failing an inside tank of this description, care should be taken not to shock the plants by with water at a temperature lower than that of the greenhouse itself.
An open tank, or a bath under the tank, into which pot plants can be stood occasionally for a thorough soak is advisable. Watering by immersion is ideal for most pot plants and for many.
Soot water is a useful mild stimulant forgrown under glass or in the open garden. Besides containing a certain amount of nitrogen which assists the growth of and shoots, soot tends to deepen the colour of the flowers and the green of the foliage. Stimulants of any kind should be given only to. Plants growing really strongly and should never be anything but very weak. A safe guide is to little and often rather than once with too strong a solution, and in the case of soot water the liquid should be dark brown.
The daily time sheet for heating, ventilation and watering is all important. Ventilators should be opened generally when the sun has warmed the house, and should be closed an hour before sundown, so that the utmost use is made of solar heat. Boilers should be stoked at sundown, so that they will be giving good heat in the coldest part of the night. Watering should be done in the morning in wintry weather, and not too freely except among bulbs and other plants coming to maturity. Evening watering is best in hot weather, as plants under glass should never have drops of water standing on them during the day unless they are well shaded.
Shading—blinds or whitewash—is important in most houses during a part of the summer, but must not remain when unwanted.
It is not possible in a short space to go fully into the detailed cultivation of all kinds of greenhouse plants. They can, however, be roughly divided into, and their general treatment outlined.
Climbing plants come, I think, first, if only because these are plants that the average amateur owner of a greenhouse neglects. The extremely decorative bougainvillea, with rose-purple or brick-red flowers—or, rather, bracts—is one of many highly spectacularsuitable for the warm greenhouse. The blue passion flower and the September-flowering plumbago capensis are suitable for the cool greenhouse. The ideal way to grow such climbers is in a soil bed thick on the floor of a greenhouse, while the plants themselves can be trained to the pillars or to wires strained horizontally along the walls of the lean-to greenhouse.