Dear Master Gardener, Can you tell me how wind chill affects the plants under a frost blanket? For instance, if I am using a 24-degree frost blanket for protection and the temp is 28, however we are having winds at 25 mph, what effect does that have under the blanket? Or how much temperature protection will my plants lose due to windchill? Thank you so much, Denise
Answer: Denise, That’s an interesting question. Frost blankets will effectively “zone up” your area one zone. It’s like a coat for your plants. However in the case of wind chill, only humans are affected by this. Wind chill estimates the amount of heat loss from warm-blooded creatures as the wind passes over exposed areas of the body. Plants do not generate heat, so essentially they are not directly affected by wind, and if under cover they would not be affected by the wind.
What can be more detrimental to your plants is the dew point. This is the temperature where air reaches water saturation. There are several scientific methods of calculating this and the numerous effects it has on vegetation. Water vapor helps to slow the temperature fall. With a high dew point, radiant heat losses are slowed, but if the dew point is low, the temps may fall rapidly. Think of how fog in an evening will make it warmer.
You can add some forms of mild heat under the frost blankets, like Christmas lights or milk jugs of water that have absorbed the sun during the day.
Hope that helps and happy gardening!