How to Warm Soil and Protect Seedlings from Frost

Reader Contribution by Rebecca Martin
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Spring is without a doubt the most exciting time of year for us gardeners. It’s the time to get sowing in earnest! But before you so much as tear open a seed packet, you’ll need to make sure your soil is warm enough and that late frosts won’t hamper your efforts. Follow this advice to triumph over the temperature swings of spring and get your fingers dirty early.

Use raised beds. Sometimes soil needs help to become warm enough for sowing in spring. Because raised beds warm up quickly, they’re ideal for the earliest sowings.

Use covers to warm your soil. Cover soil with black plastic or row covers at least one week before sowing, or protect individual plants with squares of plastic cut to size. Soil temperatures beneath will rise by a couple of degrees.

Make plastic bottle cloches. Cut a bottle in half, then place each half over a seedling. Leave the lid off the top half on sunny days, and cut a hole in the base of the bottom half for ventilation.

Fill bottles with water to radiate heat. Water-filled bottles will absorb heat during the day and release it at night, warming the air around your plants. You can also protect seedlings by filling plastic bottles with hot water on cold nights. Cluster your seedlings in a confined place, such as a cold frame, and then fill gallon-sized bottles with hot water and place these into the cold frame with your seedlings.

Protect plants with polystyrene: Polystyrene boxes can shield seedlings from extreme temperature fluctuations. At night put on the lid or lay a sheet of glass or plastic on top. Even better, make a portable cold frame by slotting lengths of plastic pipe into the corners of the box, then simply drape row cover material over the top.

Learn more about how to protecting seedlings from frost in this video.

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