Warming Soil and Protecting Seedlings from Frosts

To enjoy a strong start for your homegrown vegetables, make sure that your soil is warm enough and that you use techniques to insulate young seedlings from cold temperatures. We’ll show you how to warm your soil and protect your precious seedlings for the best possible start to your growing season.

How to Warm Soil and Protect Seedlings from Frost

Sometimes soil needs help to become warm enough for sowing in spring. Raised beds warm up quickly, so are ideal for the earliest sowings.

• Warm your soil by covering it over with black plastic or row covers at least one week before sowing. Peg it down at regular intervals with U-shaped pegs, or weigh the edges down with rocks. Individual plants can be protected with squares of plastic cut to size, or by using purpose-sold cloches. Soil temperatures beneath will rise by a couple of degrees, making all the difference for early sowings.
• You can also make your own cloches. Use sharp scissors to cut a bottle in half, then place the top half over your seedling. Leave the lid off on sunny days. You can use the bottoms of the bottles too – just cut a hole in the base for ventilation. Push your bottle cloches into the soil or hold them in place with a cane to stop them blowing away.
• Surround plants with water-filled bottles, which will absorb heat during the day then release it at night, warming the air around your plants. This is especially effective within a greenhouse, tunnel or cold frame.
• You can also fill plastic bottles with hot water on cold nights to protect seedlings. Cluster your seedlings into a confined place such as a cold frame, fill gallon-sized bottles with hot water and place these into the cold frame with your seedlings. The radiated heat from the bottle will lift the temperature inside by a few degrees.
• Polystyrene boxes, such as those used in fish markets, shield your seedlings from extreme temperature fluctuations. At night, simply put the lid on or lay a sheet of glass or a doubled-up layer of fabric over the top. Or even better, make a portable cold frame by slotting lengths of plastic pipe into the corners of the box, then simply pull row cover plastic over the top.

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