All glass structures can be heated by one of four methods, and it may be said at once that there are advantages in every kind of heating apparatus. It is idle to go into the details of such methods, as any intending builder of acan obtain full particulars from the various firms concerned. The four methods are these :—
1. Coke or coal boilers and water pipes. An old method which cannot be improved upon in the results it achieves. It does, however, necessitate considerable regular attention and care to operate this system satisfactorily.
The running costs of coke boilers are low, and in large houses it is possible, by a system of partitions, to arrange for different heats in different parts of the same structure.
2. Gas. Gas boilers, with automatic thermostatic control minimize labour, and make for certainty. They are useful for the owner gardener who wants to maintain a required temperature in all weathers with a minimum of trouble. Gas is used outside the house, and there should be no danger whatever to any of the plants.
3. Electricity. Electrically heated boilers operate in the same way as gas boilers. The use of an electric cable is a newer method of heating greenhouses and frames, and as the cables can be used in frames below the soil level, this method has much to commend it where the cost of electricity is not too high.
4. Oil heaters. Oil as a fuel for boilers is used on a large scale in commercial nurseries, which is sufficient recommendation for this type of heating. Small oil heaters for use in little greenhouses are also serviceable. The slight danger from fumes scarcely exists with some types of oil heater, and the moisture content of the air is kept up by the use of pans of water over the heaters. For all except the rarest of plants, I regard some of the modern oil heaters as very satisfactory indeed.
Ventilation is a matter for judgement both in theand frame. One point to remember is that ventilation should almost always be effected on the side of the frame or greenhouse away from the wind. No young plants like draughts, but more plants under glass are killed by coddling than by cold winds.
Ventilation and air moisture must both be considered. It is a mistake to allow air to become damp and stagnant : damping off” disease will inevitably result. Daily ventilation all the year round should be aimed at, even if the ventilation is given for a few minutes only.
Ventilation is particularly important when such plants as tomatoes are in flower. If the air is moist,will not be effective, and the fruits will fail to set. That is why tomato houses should always be opened about midday, and why, also, the grower should tap each cane along the row about the same time. Spraying overhead while the are fully open is a mistake. In the case of cucumbers, it is not desirable that the shall form, and spraying overhead is therefore permissible.