How to Heat Plants in a Greenhouse in Winter

Overview

You can build a small hobby greenhouse quickly and economically. If you simply build a frame of 2x4s and cover it with clear corrugated fiberglass, that's all you need to help extend your growing season for frost-tender plants -- such as sweet basil, potted palms and even small potted citrus trees. But the frost protection your greenhouse provides will only go so far in giving your plants the warmth they need, especially if you live in an area where winter temperatures often dip below freezing. You can heat your greenhouse by using one or more methods that won't send your electric bill through the ceiling.

Heating a Greenhouse in Winter

Step 1

Spread a thick layer of compost or other form of organic mulch around the base of your plants. It will help keep the soil warmer and at the same time will provide nutrients to your plants.

Step 2

Set plants on top of purchased heating coils designed for use with plants.

Step 3

Create a heat sink by filling gallon plastic jugs with water. Set them on the floor of your greenhouse at frequent intervals (several inches to one foot apart). They will heat up a bit during the day and then radiate the heat in your greenhouse at night.

Step 4

Hang 300-watt incandescent lights above your plants. Although they use electricity, using them is less costly than using a space heater. Their light will also benefit your plants.

Step 5

Attach some form of insulation on the inside walls of your greenhouse. Alternatives to standard insulation include egg cartons and corn stalks from last summer's vegetable garden.

Tips and Warnings

  • Although fans sound like they will make the temperature cooler, they are necessary to give your plants the air circulation they need in a warm, still environment. If you neglect to install at least one small fan, the chances your plants will develop fungal diseases are increased.

Things You'll Need

  • Mulch
  • Heating coil(s)
  • Heat sink
  • Incandescent light(s)
  • Insulation
  • Fan(s)

References

  • Hobby Greenhouse Association
  • Hobby greenhouse

Who Can Help

  • Heating coil source
  • Gardener's Supply
Keywords: greenhouse gardening, winter protection, frost tender, heat plants winter

About this Author

Barbara Fahs lives on Hawaii island, where she has created Hiā€˜iaka's Healing Herb Garden. Barbara wrote "Super Simple Guide to Creating Hawaiian Gardens," and has been a professional writer since 1984. She contributes to Big Island Weekly, Ke Ola magazine, GardenGuides.com and eHow.com. She earned her B.A. at UCSB and her M.A. from San Jose State University.