If you’re sowing seeds in March or April, you may need to warm the soil before you sow. If seeds are sown in cold soil, they won’t germinate and will rot.
Read about sowing seeds outdoors.
Different soil types warm up at different rates – open sandy loam warms up more quickly than clay. The warmth of the soil also depends on the local weather. Hardy varieties can cope with lower temperatures than half-hardy and tender plants – you can check your soil temperature with a thermometer to gauge when you can sow particular types of plant.
Here are few tricks to help warm your soil in spring.
Cover with polythene
Cover the surface of the soil with a sheet of polythene, mulch fabric or roofing felt. The protective cover will keep out cold rain and late snow and if you use a dark colour, it will absorb heat from the sun and transfer it to the soil.
Cover with a cloche
Often used to cover seeds and young plants, cloches are even more beneficial if put in place two to three weeks before sowing. They trap air, allowing it to warm in the sun, and this gradually percolates into the soil surface.
Cover with straw
The coarse structure of straw traps pockets of air, which warm up and insulate the soil from cold winds. Add a 10cm layer of straw on the soil surface and weight it down using planks, bricks or ridge tiles.