126 
THE GARDEN MAGAZINE 
November. 1916 
more than a quarter of an inch. A larger lap, 
leaves the upper glass so extended that a 
driving storm is more likely to force its way 
inside. 
ROOF SHADING 
Roof shading is quite a factor when the 
greenhouses are to be used in summer, and a 
greenhouse should certainly be used then as 
much as in winter. There are several sys- 
tems, or rather ways. One is a portable slat 
trellis placed on the outside of the greenhouse 
that can be rolled up when not in use. The 
chief objection is that they operate from the 
outside, and the distinct advantage over a 
fixed shade is that they can be rolled up on dull 
cloudy days. Sliding curtains can be arranged 
inside the house. Lines are usually placed 
along the roof and the curtains are made with 
rings attached and can be slid along as de- 
sired. They do not look verj’ pleasing inside 
the house however. Whitewashing or stip- 
pling is more common than any other method 
of roof shading. It is easy to apply but is 
very unsightly especially when the whitewash 
is sprayed on. You also have the disadvan- 
tage of being shaded at all times, whether 
you need it or not. 
THE HEATING OF IT 
grown, but clear glass is always advisable 
when you are at all doubtful, because you can 
always shade a roof and convert a growing 
house into a palm house but you cannot re- 
verse this condition without changing the 
glass. 
The glass should always be bedded in good 
putty, a small detail but a very important 
one. Poorly bedded glass will leak and cause 
considerable trouble. It is laid with both 
butted and lapped joints. The latter is pre- 
ferable; in fact, butted glass has been dis- 
carded by the modern greenhouse builder. 
The joints on the lap should be short — not 
II. 
I N EVERY greenhouse that deserves the 
name, the vital fact is that heat can be 
maintained in it in defiance of the weather 
outside. Obviously no pains should be 
spared to make this essential factor a success, 
lo save trouble and expense, and to prevent 
failure, become familiar with the principles, 
details and essentials of a heating system. 
In the first place when and where should 
the temperature be taken? In other words, 
what should the heating plant be expected to 
do? If we say that a boiler will “heat 10,000 
feet of glass to 60 degrees F.,” we mean that 
it will keep the temperature of the air enclosed 
by 10,000 square feet of glass, or its equivalent 
(including walls, doors, etc.) at a temperature 
of at least 60 degrees, on the coldest night of 
winter. In other words, the capacity of a 
heater should always be stated conservatively; 
the conditions it must fulfill include the lowest 
point to which the heat can be allowed to 
fall, when everything is most against it. 
THE .AMOUNT OF HEAT REQUIRED 
The point at which the heat must be main- 
tained depends upon several conditions, 
primarily upon the crops grown. In this con- 
nection, if no accurate information is at hand, 
it is well to recall the nature and habit of the 
plant, and if possible its native locality. 
Tomatoes, Chrysanthemums, corn, melons, 
etc., being tropical plants, naturally require a 
warm house. Carnations, Violets, lettuce, 
radishes, etc., of more Northern flora, are hard- 
ier and will withstand conditions several 
degrees lower. A rough and partial classifi- 
cation may be made as follows: 
Lettuce and Violets. 40-50 degrees. 
Radishes and Carnations, 50-55 degrees. 
Roses and tomatoes, 60 degrees plus. 
Cucumbers, melons, stove plants, 70 degrees. 
figuring, always, these temperatures as the 
mininum for good growth. There may be a 
variation of three to five degrees in the best 
temperature for any of these species according 
to the variety considered. 
A second condition influencing the work a 
heater must do is the type and condition of the 
house. A building with a rather flat or gently 
sloping roof will hold more snow and, therefore 
be harder to heat and to keep light, than a 
house with steep or curved lines. If it is an 
old house with cracked glass or gaping joints 
it will, of course, be chilly, draughty and hard 
to heat. If, on the other hand, there is but 
little wall surface or material other than glass, 
and if the latter is clean and well laid, the 
sun’s heat will be far more effective and will 
lessen considerably the artificial heat needed. 
Finally, the climate and the position of the 
house in reference to other objects is important. 
Climate can be safely planned for, but the 
difference between a position to the north and 
one to the south side of a larger building may 
make many dollars’ difference in the amount 
of coal burned. In all northern or north 
temperate latitudes the greenhouse should be 
protected on the north side — by woods, a fence, 
an orchard, a barn, or some other obstruction 
to cold winds. Such a location in spring and 
summer may seem unduly warm, but at these 
times the heat may be tempered in ways men- 
tioned below. 
MAINTAINING A GIVEN TEMPERATURE 
Because the problem in greenhouse heating 
is essentially different from that of heating a 
dwelling, it is generally unwise to try and heat 
the glasshouse from the house furnace. In 
the latter case it is during the day, when the 
occupants are moving about, that the greatest 
amount of heat is desired; at night the fires 
may be banked and kept very low. In the 
greenhouse just the opposite conditions pre- 
vail. During the day the sun affords a large 
amount of heat, the outdoor temperature is 
higher, and the furnace may be kept down. 
At night, conditions are all against the plants, 
and the fires must be kept bright in order to 
prevent a fall in temperature of more than 
ten degrees between noon and midnight. 
So long as the furnace is large enough it 
is an easy matter to keep the required heat at 
night. It is during the daj', when the temper- 
ature tends to rise above a desirable point, 
that our ingenuity is taxed to keep it within 
bounds without putting out the fires alto- 
gether. This is accomplished (a) by shading 
the plants and (b) by ventilating the house. 
The former is done by painting the glass with 
a thin whitewash, by covering it with a trellis 
made of laths or slats, or by devising movable 
cloth screens within. These can easily be 
slung on wires parallel to the glass, as in a 
photographer’s or artist’s studio. Chrysan- 
themums are often shaded in this manner. 
Ventilation is an important point in the 
management of a greenhouse, which need not 
be discussed here. It might be mentioned, 
however, that it is desirable to allow for two 
rows of ventilators — one on each side of the 
house, so that whichever way the wind is 
blowing, draughts and chills may be pre- 
vented by using the opening on the other side. 
FIGURING THE CAPACITY OF .A FURNACE 
The five factors used in figuring the size of 
the heating plant for a given greenhouse are: 
glass area, radiating surface or area of heating 
pipes, fire or heating surface (that is, the area 
over which the heat from the fire comes in 
Individual hobbies lend themselves to under glass schemes. In heated pools tropical 
Water Lilies will give their gorgeous (lowers 
Or, with the outside cold defied, an ornamental rockery or Japanese garden may be enjoyed 
all through the winter 
