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Warming soil in spring by covering with cloches or plastic sheets allows early planting and sowing, and speedier subsequent growth compared to uncovered soil. Vegetable growers and gardeners on clay soils find this technique particularly useful.
Vegetables in particular benefit from pre-warming of soils, helping crops to germinate earlier than usual, increasing the length of the cropping season. Covering the soil will warm it during the day and slow down heat loss at night.
Early crops that benefit from sowing in late winter or early spring into pre-warmed soil include:
Tender crops sown in late spring or early summer into pre-warmed soil include:
Seedbeds for ornamental plants can also be pre-warmed.
Clay soils are notoriously slow to warm up in spring, due to their retention of water after the winter. Warming can help on such soils but without ridding the surplus water it may not be very efficient. In fact, raising transplants in pots and cell trays is a more practical way to accomplish early cropping for clay soils.
Pre-warming is not difficult but does require a little forethought:
Just a few simple steps are needed to pre-warm soil:
Plastic films and cloches can blow around in the wind if not securely fitted, negating any warming effect. To avoid this, weight the covers around the edge with bricks or tuck the edge of the film into the soil with a spade. You will need to allow for this extra material when cutting the film to size.
Glass cloches can be heavy and easily broken so care is needed when using them.
Clay soilClochesFleece and crop coversHardening off tender plantsMulchingSeed: sowing outdoorsSoil: cultivation
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