This section is from the book "How To Make A Flower Garden", by Wilhelm Miller. Also available from Amazon: The Well-Tended Perennial Garden: Planting and Pruning Techniques.
We who live in the southern or south central States can keep our pets through the winter months with much less trouble and expense than our northern neighbours. Pits are inexpensive, and in this latitude most plants can be kept in them without any artificial heat. In my own I gather tea-rose buds, sweet violets, primroses, geraniums, callas, carnations, abutilons, heliotropes, and a variety of greenhouse flowers at all months of the winter, and here I start greenhouse seeds and all of my summer-flowering bulbs.
One of the most important requirements of a pit is perfect drainage. An imperfectly drained pit will give the florist much more trouble than pleasure, for during heavy rains the water will often rise, causing too much moisture for many a choice plant. If drainage pipe is used, it should be placed in one corner, and the floor should slope from all sides to the pipe, so there will be no small pools of water in any part of the pit. In my own, the drainage pipe extends for about six feet from the pit, and is covered to about four feet with earth and sod. During severely cold weather, when the air cannot be permitted to enter at any other point, this serves as a ventilator, for the air is thoroughly warmed by the time it reaches the pit. One end of the pipe should be covered with finely woven wire netting or small iron grate, to prevent the entrance of rats or rabbits.
One wishes a pit to be a permanent structure, and rock and brick are therefore much used for the walls, but such walls are not altogether satisfactory. I have mine walled with planks of three-inch thickness, and, with the exception of one top plank, the lining is as good as when put in, a dozen years ago.
For the benefit of those who intend to have a pit, I will give dimensions, so that some idea of cost can be formed. Length, twelve feet; breadth, eight feet; height of north end, seven feet; of south end, four and one-half feet. This gives a slope of two and a half feet, which is sufficient to shed water, and permits the sun's rays to penetrate without obstruction. Twenty-five planks were used for the walls, and nine for the benches. Back under the other benches, about two feet from the floor, I had two long benches placed for storing away the boxes of summer-flowering bulbs and dormant plants.
The lumber used consisted of oak planks about fifteen inches wide and three thick, with four strips eight by two inches for outside finish. A pit of this size will hold a goodly number of pots, but, as it is necessary to economise space in the early spring, I have small shelves placed in the east and west corners, about one foot and a half from the top, for bulb- and seed-boxes.
The cost of a pit is small. The digging, carpenter's work, and banking and lumber would have to be counted as the main expense. The cost of sash would be trivial, but cheap glass is quite expensive in the end. In placing benches, put them low enough to prevent the plants from touching glass, as the hot sunshine will scorch foliage. In banking earth around the pit, it must be securely packed against the plank, so there will be no airholes for frost to enter.