Plan the perfect garden with our interactive tool →

How to Heat a Small Greenhouse

...
Metal greenhouse in summer with open door image by Scott Latham from Fotolia.com

Keeping a greenhouse warm at night, or on very cold days, is a challenge. Install a thermometer so you don't have to guess at the temperature. How warm the greenhouse is depends on what you're growing. Tropical plants and warm-season vegetables like tomatoes and cucumbers have to be kept warmer than cool-season vegetables like spinach and lettuce. Spring bulbs may only need a few degrees above freezing to do well. If you live in a frigid area, space heaters may be your only heating option.

Christmas Lights

Tack cup hooks on the inside of the greenhouse away from the plastic or glass.

  • Keeping a greenhouse warm at night, or on very cold days, is a challenge.
  • If you live in a frigid area, space heaters may be your only heating option.

String old-fashioned Christmas lights, not LED lights, around the interior of the greenhouse, making sure the lights don't touch the plastic walls. Since heat rises, the lower you can put the lights the better.

Keep the lights from touching plants. Turn them on at dusk. Before you go to bed check the temperature in the greenhouse. It may be necessary to add additional lights.

Add additional lights by fastening cup hooks into wooden shelving toward the middle of the greenhouse. If the shelves are metal, tape the light cords to the shelves with electrician's tape.

  • String old-fashioned Christmas lights, not LED lights, around the interior of the greenhouse, making sure the lights don't touch the plastic walls.

Water Jugs

Fill gallon-, 2 1/2-gallon or 5-gallon containers with water. Larger containers may be used if you can find them.

Wrap the jugs with black plastic. The plastic absorbs the heat and warms the water. The warm water will give off heat to the greenhouse during the evening and night. The jugs may be spray painted black, and then you won't need the black plastic.

Stack the containers against the side of the greenhouse that gets sun most of the day. You may have to install shelving to hold the containers.

  • Fill gallon-, 2 1/2-gallon or 5-gallon containers with water.
  • The warm water will give off heat to the greenhouse during the evening and night.

Tip

A supplemental heating source may be necessary on cloudy days if you're using the water jug method.

Warning

Air circulation is important in a greenhouse as well as heating.

Related Articles

How to Heat a Plastic Greenhouse Safely & Cheaply
How to Heat a Plastic Greenhouse Safely & Cheaply
Advice for Greenhouse Gardening in Minnesota
Advice for Greenhouse Gardening in Minnesota
Greenhouse Gardening in Michigan
Greenhouse Gardening in Michigan
How to Heat a Small Greenhouse With Kerosene
How to Heat a Small Greenhouse With Kerosene
How to Grow Tomatoes Year Round
How to Grow Tomatoes Year Round
How to Sell Potted Plants
How to Sell Potted Plants
How to Seal Your Greenhouse
How to Seal Your Greenhouse
How to Landscape Around a Light Pole
How to Landscape Around a Light Pole
How to Make Your Own Solar Birdbath Heater
How to Make Your Own Solar Birdbath Heater
How to Vent a Greenhouse
How to Vent a Greenhouse
How to Heat Remote Greenhouses Without Electricity
How to Heat Remote Greenhouses Without Electricity
Cheapest Ways to Heat a Greenhouse
Cheapest Ways to Heat a Greenhouse
How to Remove Dents From an Abovegound Pool
How to Remove Dents From an Abovegound Pool
Garden Guides
×