Minimum Temperatures in the Greenhouse

Many people wonder what temperatures their greenhouses should be kept at. Below a general temperature guide is listed.

Keeping a Cold Greenhouse – The minimum temperature that can be kept in the greenhouse is 28 degrees F when outside temperatures fall to about 20 degrees F. Plants are still protected from weather elements and growth is about 3 to 4 weeks ahead of outdoor plants. However, no growth will occur in the winter, and this is unsuitable for plants that are frost sensitive.

Keeping a Cool Greenhouse – The minimum temperature kept inside the greenhouse is 45 degrees F. Plants are protected from outdoor elements, and the minimum temperature is just high enough to support plant growth. It also allows frost-sensitive plants to be over-wintered.

Keeping a Warm Greenhouse – The minimum temperature required inside the greenhouse is 55 degres F. This is the most popular climate kept because a wide range of plants can be grown during the winter months. Exotic fruits and plants can also be planted. This greenhouse will cost more to heat than a cool greenhouse.

Keeping a Stove (Hot) House – The minimum temperature required inside the greenhouse is 65 degrees F. This is advisable if you are growing tropical plants only.

Any type of heating works, propane, natural gas or electric. Light bulbs can also help heat a smaller space. Wrap the inside of the greenhouse in a layer of plastic to help retain heat.

In June, you will likely experience higher temperatures in the greenhouse due to the warmer weather. To cool your greenhouse down, water down both the inside (including the floor) and outside of the greenhouse. Misting kits or evaporative coolers can also lower the air temperature by 20 degrees F.

Most people move all of their plants outdoors from June to October. Be sure to harden off your plants before moving them. Once your greenhouse is emptied, it’s a good time to clean it.

Shelley Awad
Greenhouse Consultant
Backyard Greenhouses
www.backyardgreenhouses.com
1-800-665-2124
shelley@greenhousekids.com