Choosing Frames or Cloches
A frame — or two — costs little to buy, or make yourself, and can be fitted into most gardens. Nearly everything you grow in a greenhouse can also be grown in frames, allowing for the restrictions in height and size.
Even if you have a greenhouse, frames can take over much of the work to leave more space for decorative plants and those demanding full greenhouse height.
First you must decide whether to buy a ready-made frame or make one yourself from a frame kit of glass-to-ground design with timber or metal sections. An all-glass frame is suitable unless you want extra warmth for propagation, or for growing cucumbers or melons.
Lids, known as ‘lights’, can be bought separately and you can place these over your own timber or brick-built sides, or even set one over a pit dug in the ground, adding to it as required. The lights can be easily stored away in the summer, when not in use.
Modern frames are often fitted with sliding glass sides, to give access or for added ventilation, and lights that slide aside as well as lift up so that they can be removed completely for easy working.
Choice of material
Aluminium alloy framework has many advantages: it is long-lasting, requires no maintenance and, being lightweight, is ideal for moving about. If you prefer timber, choose wood that is noted for its weather resistance, because frame sides are likely to come into contact with damp soil for long periods. Avoid soft woods treated with creosote as the vapour continues to be harmful to plants for some time. Green Cuprinol is suitable, but before using any other preservative check the maker’s literature to be sure that it is safe for plants.
Plastic, instead of glass, for garden frames is light, easily portable and obviously advisable where small children are using the garden. From a gardener’s point of view, however, glass has many advantages. You must use glass if the frame is to be heated, and would be advised to do so in windy areas as plastic can blow away.
Siting the frame
If you use a frame as an adjunct to your greenhouse (and it has vertical sides), you can push the frame close up to one side. This helps to reduce warmth loss from both the greenhouse and the frame.
If using a frame for greenhouse and pot plants, put it in a shady place —against the north side of your greenhouse is ideal. But most vegetable crops, and those alpines which you may be housing in frames when not in flower, prefer a bright, open position.
With many frames it is often convenient to set them back-to-back, or alongside each other in rows. To obtain more height, stand your frame on a base of bricks or concrete blocks, or place it over a pit (providing you make sure that water does not collect in it).
Electric soil-warming cables
Frames do not have to be `cold’ you can heat a large one with a small paraffin lamp provided you take great care to see that there is always ventilation. But installing electric soil-warming cables is by far the best method. Lay them in loops across the floor of the frame, making sure that they do not touch each other. Place a little sand on top and keep it moist: this will hold the cables in place and conduct the warmth more uniformly. Use only about 2-3cm (1 in) of sand, then a thermostat can be installed above the sand level to control the frame’s temperature.
If you need extra warmth (as for pot plants) run cables round the frame sides as well. With glass-sided frames, fasten the cables to wooden battens with cleats and thrust the battens into the ground.
If you are growing plants to be rooted into a deep layer of compost (such as salad crops, cucumbers and melons) site the warming cables near the bottom of the compost. In this case a thermostat of the rod type should be thrust into the compost. Temperature can also be controlled manually or by a time switch. The considerable bulk of compost will hold warmth over the periods when theis off.
Wattage depends on the size and purpose of your frame; decide after you have consulted the suppliers of such equipment.
You can use small heated frames inside the greenhouse for high-temperature propagation, or for housing a small collection of low-growing tropical plants. An aluminium framework, glass sides and top, and 2-3cm (1 in) or so of sand over the cable, are recommended. Therequired is usually about 20W per 1000 sq cm (20W per sq ft) of frame floor, and a thermostat is essential.
If possible, avoid using soil. Instead, line a trough or pit with polythene sheeting, slitted here and there for drainage, and fill it with a proprietary potting compost. You can grow excellent, high-quality salad and other crops with little risk from pests or diseases.
Where you are moving pots or other containers in and out, firm the floor and cover it with polythene, over which is spread coarse sand or shingle. If you keep this damp, it will moisten the air in the frame; the polythene will help to keep out soil pests.
Grow house plants, and pot plants like cineraria, calceolaria, primula and cyclamen, in frames until the decorative stage when they are ready to transfer to the house,or greenhouse. Use frames to raise bedding plants and for many forms of propagation from cutting and seed. You will also find them especially useful for crops like lettuce, radish, beet and carrots that you want in the kitchen even before winter is over.
Keep plants like dormant fuchsias, chrysanthemums and pelargoniums (that are used for summer garden or greenhouse decoration) in frames during the winter when they often look far from attractive. Store dormant tubers and bulbs there to leave the greenhouse less cluttered. Some crops, like strawberries and violets, lend themselves particularly to frame culture.
Keep glass frames (and cloches) as clean as possible to admit maximum light and discourage plant pests and diseases. Remove any mud splashes by careful use of a hose, if necessary.
Early cloches were of glass and often held together by clumsy wires that were difficult to manipulate. Modern designs are simpler and often make use of plastics, which are very suitable for this purpose as cloches are frequently used only for weather protection, high temperatures being rarely necessary.
Select your type
There are tent, barn and T-shaped cloches, and a flat-topped ‘utility’ one. These are usually held together by special metal or plastic clips. Some cloches can be opened for ventilation or for watering, others have perforated tops to allow the rain to enter. Plastic ones with a cellular structure give greater warmth retention.
You can make simple and effective tunnels, ideal for protecting rows of vegetables, by sandwiching lengths of polythene between wire arches at intervals along the row, or by aligning ordinary cloches end-to-end. Anchor your plastic ones carefully in windy areas as they can easily blow away; use stones, bricks, wooden or metal pegs, or some special cloche fitments.
Cloches are most useful from autumn to late spring for providing protection from excessive wet and cold. Set them in place to dry and warm the soil before you dig and fertilize it, in preparation for sowing or planting.
Use individual cloches for protecting isolated tender plants (such as fuchsia) in beds and borders, and protect groups of hardy and half-hardy annuals until they become established. You can also root cuttings directly into the ground of a nursery bed if you use cloches to cover them.
Many flowers grown for cutting benefit from cloche protection, especially low-growing bulbs in pots or bowls. Other favourite cloche flower crops are anemones, hellebore (Christmas rose), lily of the valley, violet and polyanthus. You can harden off bedding plants under cloches if frame space is not available. Also use them to protect sweet peas in the early stages.
In the vegetable garden, cloches give you year-round cropping. If you plan carefully you can move them from one crop as needed, thus putting a limited number to maximum use.
Working with cloches
You do not need to remove cloches for watering; the water that drains off them will seep into the soil provided that it has been well prepared. It should be porous and moisture-retaining, but well-drained. Work in plenty of humus-forming material, like peat or rotted garden compost. To avoid the wind rushing through your cloche tunnels, block the ends. This also applies to individual cloches used as miniature greenhouses to cover single, or small groups of, plants. When the weather permits ventilation, move the cloches along to leave a small gap between each one and remove the ends of tunnels.
Leave plenty of room between rows for comfortable access and keep the soil along the sides of the cloche rows well hoed to allow water retention. Soluble fertilizers can also be applied along the outside edges of the cloches.
Store, glass cloches, and plastic tent and barn types, on their ends and stacked inside each other. For this purpose put down some clean boards (or lay a section of concrete) in a corner of the vegetable plot, and cover it with roofing felt for glass cloches.