Cold Frames: Gardening
Like a greenhouse, ‘cold glass’, in the form of frames or cloches, makes it possible to grow plants out of season. Seeds germinate better under glass when weather conditions are unfavourable, and the less hardy plants can be protected and kept warm.
Cloches, being portable, are perhaps easier to manage than frames. However, frames preserve warmth more effectively, and so enable a wider range of plants to be grown.
The three types of frame most commonly used are the wire sectional frame, the permanent frame, which can be heated, and the type covered by Dutch lights. Movable frames have sides made of wood, the sides of the permanent type of frame being made of brick or concrete. Frames are generally 2-½ ft. high at the back, and 2 ft. high in front; a back wall that is too high will throw too much shade, and will also make it difficult to keep a level bed in which every plant lies at the same distance from the glass. The light covering the frame is usually 3 ft. wide and 5 ft. deep.
A cold frame should always face south and should be provided with a hessian blind for protection in winter, and sometimes from direct sun in midsummer.
Take great care when watering plants grown in frames, because there is little space between theand the glass and the atmosphere can therefore quickly become saturated.
Never water in cold, frosty weather, and keep the soil fairly dry. In midsummer, however, when it is sunny and hot, remove the lights completely to prevent the air drying out, and then water as necessary.
WIRE SECTIONAL FRAME
The best portable frame is the sectional wire frame, or ganwick, sometimes known as a flat-topped cloche. As well as being easy to move, these cold frames are convenient in that they allow both rain and the maximum amount of light to reach the plants; they have automatic ventilation; and they are inexpensive.
The best type of sectional frame is known as the Double 18, which is 1-½ ft. high and can be assembled in any length. The averagewill accommodate three rows of these frames, each 10 ft. long. The crops can easily be reached if the single square of glass that covers each section of the frame is re-moved.
If three frames are used, the first could hold lettuces from October to January and could then be moved to a new site for. Remove the top panes of glass in June, and the plants will continue to crop until October when the frame is needed for lettuces again.
The second frame could take radishes from October to January, and could then cover lettuces, on a new site, until April. These could be replaced by tomato plants, set out l ft. apart and trained along a stout stake running almost horizontally, which will crop between July and the end of September, when the sectional frame should be moved again in preparation for a new sowing of radishes.
The third frame could be used for raising such vegetables as cauliflowers (sown in September), Brussels sprouts, leeks, lettuces and onions (all sown in January). All these vegetables should be planted out-of-doors in March. Then move the frame to accommodate runner beans down the centre and dwarfon either side—sow a dwarf variety of runner bean, like Hammond’s Dwarf Scarlet, or remove the frame when the beans need the extra height. In June, when these no longer need cover, move the frame again to cover six plants, which will yield a heavy crop later in the summer.
THE PERMANENT FRAME
A permanent cold frame is built with brick or concrete sides, and is used for raising seedlings of all kinds, as well as for rooting cuttings that require only slight protection. Tender plants that have been raised from seed in the greenhouse will harden well if moved to the cold frame in April, before finally being planted out in the garden in late May or early June.
Use the cold frame also to protect tender herbaceous plants during the winter, or to grow early crops of carrots and radishes.
Pot plants that have finished blooming in the greenhouse may be rested in a cold frame during the summer.
A permanent frame may be heated with hot-water pipes, or by electricity, in which case special wires generally run through the soil. A heated frame is extremely useful for raising plants of all kinds, for early salad crops, and for such crops asand , which need heat if they are to be produced early.
THE DUTCH LIGHT FRAME
The Dutch light frame has as a foundation a simple wooden box framework, 15 in. high at the back and 9 in. high in the front. The most convenient size of frame will accommodate three separate Dutch lights on wooden frames, which should fit snugly into the box frame. A Dutch light is a simple wooden framework with sides grooved to receive a single sheet of 2-I-oz. Glass, 4 ft. >s in. by 2 ft. 4-1/2 in. To prevent the lights from being blown off, secure them with wires nailed to the frame. Treat the wood of the framework with Cuprinol, but never with creosote, which may damage the plants.
The soil under the Dutch lights should be rich in organic matter, and it is advisable to fork into each frame 1-½ bushels of fine peat and l lb. offish manure with a 6 per cent potash content. When the soil has been prepared, place the glass over the frame to warm the soil before sowing. Place Dutch light frames in a sheltered spot where they will receive unobstructed light. They are not, of course, automatically ventilated, so use wooden blocks to raise the frame lights at the bottom or at the top, depending on the direction of the wind. Open the frames at 9 or 10 o’clock in the morning, depending on the time of year, and close them when the sun sinks. Never ventilate when rain might drive in, or when there is fog or frost. After a sharp night frost, however, open the lights at the bottom so that some air enters before the sun gets strong enough to cause a sudden thaw, which may damage the plants.
A triple Dutch light frame might be used as follows: one light for lettuce from late September until December, followed by radishes until April; the other two lights could hold carrots from October until April. From April until the end of September all three lights could be used for dwarf.
Alternatively, dwarf beans would grow from September to November, followed by lettuce and cauliflower until late April. From May till September, one light could be devoted to melons, and the other two to cucumbers.