Home Gardening Techniques How to Keep Your Soil Warm in Winter: A Comprehensive Guide to Soil Heating Cables

How to Keep Your Soil Warm in Winter: A Comprehensive Guide to Soil Heating Cables

by Gregory
4 minutes read

How to Keep Your Soil Warm in Winter: A Guide to Soil Heating Cables


Do you want to extend your gardening season and grow plants even in the cold winter months? Soil heating cables are a great way to do just that. By providing consistent warmth to the soil, you can protect your plants from the cold and help them thrive.

Why Warm the Soil in Winter?

There are many benefits to warming the soil in winter, including:

  • Extending the growing season: You can start planting earlier in the spring and harvest later in the fall, or even grow plants year-round.
  • Overwintering plants: You can protect plants that are not fully hardy from the cold and keep them alive until spring.
  • Starting transplants or root cuttings: You can get a head start on your gardening by starting seeds or taking cuttings indoors and then transplanting them into the warm soil in the spring.
  • Hardening off transplants begun indoors: You can help your indoor-grown plants adjust to the outdoor environment by gradually exposing them to the cold in a warm soil bed before transplanting them into the ground.

Structures to Use with Soil Warming Cables

Simply adding cables to an open garden bed is not very effective, as the soil will lose heat to the air. Instead, it’s best to use cables within a structure that retains heat, such as:

  • Cold frame: A small, enclosed structure that is typically used to start seeds or overwinter plants.
  • Hot box: A larger, insulated structure that can be used to grow plants throughout the winter.
  • Plastic tunnel: A greenhouse-like structure that can cover a larger area and provide protection from the elements.

Choosing Your Cables

When choosing heating cables, consider the length and wattage you need. The length of cable you need will depend on the size of the area you want to heat, and the wattage will depend on the climate and how much heat you need.

  • For milder climates, aim for about 10 watts per square foot.
  • For colder climates, go up to 12 watts per square foot.

Spacing the Cables

To determine the spacing between the loops of cable, multiply the watts per foot of the cable you purchase by 12 and then divide that number by the wattage per square foot you want for your bed. This will give you the spacing in inches between loops of cable.

How to Install Soil Heating Cables

To install soil heating cables in a cold frame or similar structure:

  1. Choose a location where you can easily plug in the cables.
  2. Dig down and remove soil to a depth of 6 to 12 inches.
  3. Fill the space with about 4 inches of sand.
  4. Lay the cable on top of the sand, spacing the loops according to your calculations.
  5. Cover the cable with more sand and hardware cloth.
  6. You can then put containers right on top or add potting soil over the cloth and plant directly in the soil.
  7. Attach a thermostat to the cable to track the temperature and adjust the settings as needed.

Safety Precautions

Using heating cables is generally safe, but it’s important to take some precautions:

  • Never cut or splice a cable.
  • Ensure that the cables will not touch and overheat.
  • If you are unsure if you can do the installation safely, hire an electrician.


Soil heating cables are a great way to extend your growing season and protect your plants from the cold. By following these tips, you can safely and effectively install and use soil heating cables to keep your soil warm in winter.

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