The use of the hot-bed for growing seeds of subtropical and other seeds is noted in prior section (12. Seeds in the Hot-bed). At the home place, and in commercial gardens, the hot-bed is used mainly for growing tomato, egg-plant, pepper, flowers, and many other plants. Even where large areas are occupied by what are known as forcing pits, as shown by end section in Fig. 28, the hot-beds and cold-frames are not dispensed with. But it is so cheap and simple in construction that it is found at the homes of amateurs across the continent and its use is on the increase. After the first crop, when the bottom heat has lessened, it is useful for rooting cuttings of immature growth or those of dormant woody growth.
Fig. 28. - End view of forcing pits heated by hot-water pipes.
In making and filling the pit a few essentials must be kept in mind : (a) At the North the pit should be dug in the fall and filled with coarse manure to prevent freezing. In digging make it large enough for the frame to set on the filling so as to settle as the manure goes down. The commercial hot-bed sash are three feet wide and six feet long. For a bed with three sash the pit should be excavated nine feet and six inches long, six feet six inches wide, and thirty inches deep, for ordinary home use.
(b) When the time arrives for starting the heat the filling is taken out and about twenty inches of horse manure are put in. This should be well fined and placed in layers evenly so as to secure even settling when the frame is put on. If the filling is quite dry it is best to wet the layers as placed to give the needed moisture.
If forest leaves are obtainable it is best to mix them with the manure in filling. (c) The frame is made, as shown in Fig. 29, with the back six to eight inches higher than the front, to favor the reception of the sun's rays and to carry off rain. When the frame is set on the filling, and the first intense heat has subsided, fill in with six to seven inches of mellow, rich, well-fined earth. (d) Ventilation when the sun shines by moving sash is essential and watering must not be neglected. Fig. 29 shows the frame covered with lath for shading.
Fig. 29. - Hot-bed frame, covered with lath frame later in the season.