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.
Coldprames are not sufficiently appreciated by the general horticultural public. Under proper management so much can be done with them to lengthen the outdoor season of flowers and vegetables, in both spring and fall, and so many things can be safely carried through the winter with them, that it seems a pity they are not more generally used. Even where greenhouses are run, coldframes are of great service in aiding their work.
Coldframes may be very cheaply constructed where parties are willing to renew them every few years, or they may be substantially built where long-continued use is required. In the former case, cheap "box boards" may be used for the sides and ends, with spruce two by two-and-a-half-inch strips for the cross-pieces to support the abutting edges of the sash. For substantial structures it is well to build the front, back, and ends of brick, twelve inches in thickness, with a four-inch air space in the center, with sufficient cross-tie bricks to make the wall strong and secure. These walls should be covered with planks securely fastened by bolts built into the wall. To these planks the cross-pieces or rafters are fastened. Two by three locust pieces are best for these. The back should be twelve inches higher than the front for the ordinary six-foot width, to give good rain-drainage and an advantageous exposure to the sun. The planks on front and back walls should have the same inclination, so that the sash may be easily slid upon them.
Cheap but effective pits for wintering tender shrubs. They are protected by a windbreak of willows. The straw and matting are used in very cold weather.
The ordinary commercial sash is three feet wide and six long. The glass may be six by eight, where the sash is liable to rough usage, or ten by fourteen where it is carefully handled and well protected. There will be three rows of the larger glass and five of the smaller. The larger glass gives rather the better results.
The writer knows of no better way to give an idea how coldframes maybe used than to state just what the row with which he is most familiar contains in early winter. This row is one hundred and twenty feet long and is covered with forty sashes. It fronts southeast, and is well protected from cold winds. This position is better than any other, as the morning sun is more potent than the afternoon.
At the west end of the frames there are four sashes of violets - two of Marie Louise, and two of a very large and double Russian variety. These were rooted offsets planted in June last. The plants made a good growth during the summer and autumn, and are now full of buds which will give splendid bloom in the early spring. Next are four sashes of pansies. The plants were set in October, and will give a grand bloom in February if the weather is favourable, or in March and April if the season is backward. There are three sashes of English daisies, grown in the open ground from offsets of the choicest selected plants grown the previous season from seed. These were planted in the frames in September and are now full of bloom. The bloom will continue until next June. This daisy is more valuable than is generally known. Next are three sashes of polyanthus. These will give a wealth of bloom throughout the spring. This plant is generally hardy in the latitude of New York City, but it is desirable to have the flowers before the outdoor bloom.
Then follow six sashes of lettuce of the variety known as mignonette. Three of these were planted in September, so as to be advanced to heading when winter set in. These will be in prime condition for use in February and March. The rest were planted six weeks later, so as to be strong plants through the winter, to head up in April and May. The most solid, hard-heading sorts, that must develop very slowly, attain a higher quality in coldframes than when grown in any other way.
Next are two sashes of tea-roses, stored for planting out-of-doors for summer bloom. Tender and half-hardy roses can be carried through the winter in coldframes in the best condition for summer bloom. They can be packed closely, with a sprinkle of dry leaves among the tops.
Then follow ten sashes of cauliflowers, five in a row, with rows twenty inches apart. These were put in about October 1st, and will head in April and May. Between these rows are two rows to each space of savoury-leaved spinach. This was transplanted closely in rows in time to be at the best development in November. It keeps in perfect condition for use all through the winter, and attains a quality never found in outdoor spinach. When it is removed, the ground is entirely occupied by the cauliflower.
The last space of five sashes is occupied with sweet peas in rows two feet apart. The seed was put in early in October, so that the plants were five or six inches high at the beginning of winter. They remain dormant until spring, when they grow slowly. Here and in the cauliflower and rose spaces the soil is two feet below the glass. As the vines grow, short brush is used to support them until the glass is reached, when the sashes are removed. The plants will stand light freezing without injury. The rows are then carefully set with tall brush, and the finest of fine blooms come about the middle of May. The flowering will continue until the earliest outdoor blooms are ready. At no other season are the sweet peas so much appreciated.
As space is made vacant by the removal of lettuce, seeds of lettuce, beets, cauliflower, cabbage, cucumbers, and muskmelons in pots, and other things, are put in for the plants to be set outside for early use. Flowering annuals may also be started.
With greenhouses devoted to flowers and vegetables, the writer has found that these coldframes "pay" better than any other space under glass. Coldframes may be on any scale desired, from the three or four sashes of the beginner to the market gardener's hundreds. The writer once asked a market gardener who grew lettuce very extensively how he could afford to pay such heavy rental. He replied: "You see those frames. Every eight inches square of their space has six five-cent nickels in a little pile in the ground. I rake them out each season. You can figure it for yourself."
The labour in caring for coldframes is but slight, but the requisite attention they must have. This consists almost entirely of two things - water and ventilation. They must have air on pleasant or sunny days, and they must have water when that is necessary. Too frequent watering is very injurious.
For extremely cold weather protection is advisable. Covers made of tongued-and-grooved pine boards, one for each sash, are the most convenient and durable. Mats made of straw are warmer, but these get soaked with rain and then freeze into unmanageable nuisances. Straw mats with board covers are the best of all devices.
A sandy loam, with plenty of well-rotted manure, is the best soil for frames.