Growing Crops in Garden Frames
The small area covered by a garden frame is often the most intensively cultivated part of a vegetable plot. By careful planning, a succession of food crops can be grown in a frame throughout the year.
If you have a greenhouse, or if you plan to germinate seeds indoors, the frame is also an essential halfway house in which In harden off, or acclimatise, plants before they go to their permanent positions outdoors.
With good management, the frame should never be empty. For instance, during the winter it can be used for protecting cauliflower plants that will be set outside in early spring, or for lettuces to heart up in the frame in early April when they are expensive in the shops.
Seeds of onions and lettuces can be sown in January, two months earlier than in open ground.
After the onions and lettuces are planted out, their places can be taken in April by French and runner beans. These, in turn, will be planted in the open, to be replaced by cucumbers or melons that will grow in the frame during the summer.
When harvesting is complete, the time has come to restart the cycle and sow cauliflowers and lettuces to overwinter in the frame.
By laying electric soil-warming and air-warming cables, the frame becomes a miniature greenhouse and the gardener’s scope is widened even further.
Types of frames
Garden frames are obtainable in a wide variety of sizes and materials. There are four main types: wooden frames with glass tops (called lights); aluminium frames with glass or PVC lights; frames made of galvanised steel, with a similar light; and frames made completely of transparent plastic.
Each type has its advantages and disadvantages.
Fitted with glass lights, these are the most efficient in conserving heat. Most are made from cedar, which has natural resistance to rot and insect attacks. On many, the lights slide easily backwards or forwards on runners to provide ventilation and give access to the plants.
These frames last for many years but they are slightly more expensive than those made from aluminium, galvanised iron or plastic.
Can be fitted with glass or acrylic lights. Acrylic is cheaper and a better buy in a garden where children play ball games. The advantage of aluminium frames is their lightness, which makes them easy to move from one part of the garden to another, and the fact that they need no maintenance.
About the same price as aluminium and, although a little heavier, they too can be moved easily from one place to another.
In addition to being the cheapest, they let in the most light. They lose heat quickly at night, however. This makes them of more use in the shorter, warmer nights of spring than in the winter.
A simple, home- made frame can be constructed from odd pieces of wood, some chicken wire and a sheet of heavy-gauge polythene. A practical size is about 3 ft (1m) square with the back wall 16in (405 mm) high and the front 12in (305. mm) high.
Staple the chicken wire tautly to the top and fix the polythene over this with drawing pins. The wire will prevent the polythene from sagging under the weight of rain water.
For access to the plants, simply lift the frame to one side.
Siting and management
Choose a sunny position, preferably sheltered from cold winds. If the frame has a single, sloping light, face this towards the south.
Prepare the ground thoroughly some weeks before planting by digging in well-rotted manure or compost at the rate of a bucketful to the square yard. Just before planting, rake into the top a general fertiliser at 3 oz per square yard (90g per square metre), together with about half a bucketful of moist peat.
The manure and the peat will ensure that the ground is suitably moist for overwintering crops, which should not be watered until they start to develop in spring.
During late winter and early spring conserve heat in aluminium or galvanised-iron frames either by lining the inside walls with polystyrene sheeting or tiles, or by drawing up soil round the outside.
During frosts, cover the light of any type of frame with sacking or some similar material, removing this during the day. In warm spells open the light to let in air, and close it again in the evening.
Scatter slug pellets in the frame after sowing and planting, and make regular inspections for other pests while plants are growing.
Growing in heated frames
If you cannot afford either the money or the space for a greenhouse, a heated frame provides a worthwhile alternative. Use it in conjunction with an unheated frame or cloches, where plants will be hardened off before being put in their permanent positions.
Soil-warming cables laid under the surface will hasten early crops and give the right conditions for sowing at least a month earlier than in the open.
However, soil-warming does not provide full protection against frost. On cold nights cover the frame light with sacking, layers of newspaper or some other insulating material.
Alternatively, install air-warming cables on the inside walls of the frame, supplementing those warming the soil, to give frost protection.