As stated early in this article, greenhouse architecture and construction has become of such importance that it is now specialized, and no matter how well posted and experienced a florist may be - and building is with some a hobby- it will pay him to send a rough sketch to some horticultural builder, who will get out all his material so that his own help or a country carpenter can put it together. This should be done in every case, large or small. The following suggestions may be of help in some cases.
The ventilation of these houses, or any house, should be ample always. You may not need it except in summer, but you want the means for the largest amount of ventilation that is of benefit to the plants in the hottest weather. Our prevailing winds are from the west, and a large proportion of the country is the same. In houses running north and south, we ventilate on the east side-, especially when the ventilator is hinged at the ridge. There is also another advantage in ventilating on the east side. In February and March particularly, the thermometer may indicate 15 degrees of frost, yet the sun be very bright, compelling us to put on a crack of air by 9 or 10 o'clock. The ventilators, if on the west side, would be frozen and could be lifted only with great trouble, while the sun has thawed the ice on the east side. We do not think that ventilation on both sides is necessary if ample is given on the east side.
In houses running east and west, which most rose and carnation houses do in the north, the ventilation is usually at the ridge and on the north side, because if on the south side and there was a cutting wind from the north it would be felt on the plants; the raised ventilator prevents that. With a number of commercial rose houses, we have found ventilators opening at the ridge on the north side the most satisfactory.
The dimensions for ventilators on a 20-foot or 22-foot house should be two feet six inches deep from ridge to bottom of ventilator, and continuous the whole way along the roof. It is plain to everyone that a 3-inch opening the whole way is far better than a 6-inch opening for the length of four feet, and then a space of five or six feet with no opening. We have seen some very clearly defined cases of failure of late that were unmistakably traceable to very inadequate ventilation. It costs no more in glass and little more for the machines that operate the sashes.
In rose houses the better method is doubtless mat where the ventilator opens at the ridge, and with plants of a tropical nature, like our palms, dracaenas, orchids, ferns, etc., it must also be the better system. For carnations and the more cold-blooded plants, such as the azaleas, lilies, and our geraniums, the ventilators hinged at the ridge will do, but if all the ventilators open at the ridge for every house you won't be far wrong.
I cannot see any use in cutting off the bars where the headers go in for the ventilators to be hinged on, or it may be close on. Let all the bars run up to the ridge; you will get as much ventilation, the bars will be stronger, you will have a straighter roof, and the labor is only a trifle more, if any.
Usually plant houses lead out from a continuous shed, which is of course on the north end of them, so that there is not a square foot of bench room that has not the full light; more particularly is this true of the 22-foot houses, where the benches are removed from the walls.
Where several of these houses are built parallel and attached, only the two outside ones can spread, and this brings us to the question of