SUCCESSIONAL GROWING - Vegetable, Fruit and Herb Growing in Small Spaces - page 18

Fig. 9. Coldframes.
(1) Wooden box frame with polythene lid.
(2) Purpose-made aluminium and glass coldframe.
(3) Home-made frame.
There isn't much volume in a coldframe to hold the warmth overnight so insulating with
fleece, old net curtains or even newspaper will help to avoid a sharp drop in a frost. The soil
will be quite cold in late winter and early spring, so if you can get some sheet polystyrene and
lay it on the base you'll keep the coldframe warmer. One good source is electrical appliance
retailers who have loads of polystyrene sheets from packing materials they just throw away.
You can build your own coldframe with wooden sides and line the base and sides with
polystyrene. Not just warm, the white sheets will reflect light as well which helps the plants
grow.
The top can be made from glass. Watch out for someone having double glazing fitted as
the old windows can have a new lease of life in your coldframe. Sheet plastic is the thing to
use if those pesky pets or children are a problem.
With a little ingenuity you can also construct cloches to fit individual pots and tubs. Take
some stiff wire, an old wire coathanger or some thick stiff electrical cable and form into a
circle. Fix some thin canes from the wire to form a pyramid and then wrap some flexible
clear plastic sheet around. How decorative will depend on your skill. A good source for the
plastic sheet is a camping supplies shop where it is sold as groundsheet. With square tubs the
construction process is easier as you can use thin strips of wood as the base which is easier to
fix the canes to.