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Agriculture Methods: Keeping a Winter Greenhouse Warm

This unusually cold winter has brought many challenges to our farming operations here in Central Texas. This past November we built a new greenhouse at our headquarters and all the extreme temperatures brought by this unique Texas winter have made it a challenge to keep it warm. The seedlings need a constant warm temperature for germination while maintaining enough ventilation for the soil moisture. The seeds we are starting (Bok choy, kale, collards, broccoli, kohlrabi, cabbage and swiss chard) have an average seed germination temperature of about 60°F and with so many sunless, cloudy and cold days, it has been rather difficult maintaining that temperature.

But this wasn’t quite enough. Since we have about 75 trays of seedlings going in our greenhouse, we needed a simple and cost-effective way to generate heat. So this week we are building heating pads from three materials: 3/16 inch voltage cable staples, 3/4 inch foam board, and 24 ft heating cables. We will be stapling the heating cables to the foam board in a spiral, being careful not to let the cables touch. The cables use 3.5 watts per linear foot and a built-in thermostat automatically activate the cable when the soil temperature drops below 60°F. These heating mats will be helpful not only during freezing temperatures but also for increasing the growth rate for seedlings during already warm days.

We are hoping the freezes have passed for the winter, but if another comes around, we’ll be prepared!

If you’d like to learn how to make your own heating coils, check out this video.

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