In these progressive times it is not well to lay down hard-and-fast rules with regard to the best type of appliance. It should, however, be urged that every Orchid house ought to be heated with hot water, and, that in all cases 4-inch piping should be used, the radiation of heat from that size being much more gentle and equal than from smaller pipes. Bottom heat by means of piping under closed-in beds of cocoa-nut fibre, or any other material, is bad, although, in a very slight degree, some arrangement of the kind may be of assistance in the house devoted to raising seedlings. If it is used, an outlet must be provided for the inevitable moisture thus raised so that it will not condense and fall on the plants.
For small houses or blocks of houses, the old saddle boiler in some form is all that can be desired; and there are several forms of slow-combustion boilers which may be set almost on the surface of the ground outside the house, and these are satisfactory. For blocks of houses the English form of sectional boiler is one of the very best; in large blocks duplicate sets of this pattern, or any other type that may be selected, should be set down, as it provides means of heating the houses if the ordinary boiler happens to fail. It is always better to provide more power than may appear absolutely necessary, and work it at low pressure, than to have barely sufficient power and work it hard during severe weather, as the heat diffused in the latter case is harmful.
Before deciding on the means of heating to be employed, it would be well to pay a visit to some of the collections noted for the excellent condition of their plants, and inspect the appliances and their arrangement. Most Orchid growers, whether in private establishments or nurseries, are willing to assist amateurs in these matters. When the apparatus has been got into working order, tests should be made to ensure an equal distribution of the heat from the piping. If a draught of hot air to any part of the house from beneath the staging is observed, it is a good plan to build up openly-laid screens or brick walls 4-1/2 inches thick, the layers of brick being placed so that there is half the length of the brick opening between each brick and the next to it. Where there is a sufficient command of heat, these openly-laid brick walls, without mortar, built up below the side staging and running parallel with the edge of it, if they are syringed frequently, assist materially in preserving a healthy moisture in the house.