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How to Heat Indoor Plants

Temperatures inside are often not perfect for the best plant growth. Whether you are starting seeds indoors or trying to keep a warm-loving house plant healthy, higher temperatures are necessary. Soil temperatures are usually cooler than the surrounding air temperature, and the roots are what need heat most when starting many summer plants from seed or growing tropical house plants. Providing the proper warmth ensures the plants grow strong and healthy.

Set seedling trays on the seedling heat mat, available from garden stores and seed suppliers. Set most plants on the mat after they have germinated, except for peppers and other heat-loving vegetables that need bottom heat to germinate.

Set the temperature on the mat to the recommended growing temperature on the seed packet. If no temperature is indicated, most seedlings do best at 70 to 75 degrees Fahrenheit. Leave the mat on for 24 hours a day until the seedlings are ready to plant outside or into permanent pots.

Use a seedling heat mat during the daytime for established house plants. Set it between 70 and 80 degrees Fahrenheit or follow the recommendation on the plant tag if provided. Turn the heat mat off at night when plants require a lower temperature.

Check the moisture level in the container every two to three days, as bottom heat dries the soil more quickly. Water as needed to maintain soil moisture.

Place the plants away from areas that are not prone to drafts from windows or air vents. Cool air is drying and lowers the temperature around the plant. Grow seedlings under grow lights so the cool air emanating through window glass doesn't damage them.


Plug heat mats into an automatic timer when using them for houseplants. This way you don't have to remember to turn them off and on.


Avoid using heat lamps. These dry the plant and may burn the foliage. If you must use a heat lamp, leave it on for only two or three hours a day and mist the plant with water regularly to maintain humidity.

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