Prepare for Freezing Temperatures

As you prepare for the holidays, it's also a good time to prepare for potential frost in your yard and garden.  This preparation consists of having the knowledge and materials you need to protect your sensitive plants.  There are several actions you can take to protect your frost sensitive plants and trees from damage when a freeze is predicted. 

• If possible, move the plants close to your home.  During the day buildings absorb heat which they then radiate.
• Keep the soil around tree trunks free of ground cover, weeds, and mulch since bare soil radiates more heat.
• Keep the soil moist since moist soil retains heat better than dry soil.  Ideally, you should irrigate the soil two to three days in advance of a freeze so it maintains the proper water content for maximum absorption of solar radiation.  Avoid watering your plants right before a freeze because if the surface is wet, it increases evaporation and the energy loss from the evaporation counterbalances the benefit of better solar radiation absorption.
• Don't water succulents right before a freeze.  Because of their ability to retain high levels of water, it increases their risk of ice crystals forming and bursting in their cells.
• Insulate the trunks of young trees by wrapping them in cardboard, fiberglass, or foam pipe insulation.
• Before the sun sets, cover sensitive plants and trees with floating row covers, nursery foam covers, burlap, or sheets or blankets.  (A double layer of row cover or nursery foam cover can provide up to 10 degrees of protection.) If using burlap, a sheet or blanket, use stakes, tomato cages or other supports to keep the fabric from weighing down the foliage on the tree or plant and to allow greater air flow. Note that if the material you use as a cover gets wet, it could lead to colder temperatures near the fabric. Be sure to remove the cover during the day to recharge the heat in the soil, and to allow the greenery to absorb sunlight.
• Place old style holiday lights in the interior of trees to help raise the temperature up to 3 degrees.  Be sure to use lights and power cords rated for outdoor use.

 For more information on protecting sensitive plants from frost, check out the document “Frost Protection for Citrus and Other Subtropicals” from the UC Division of Agriculture and Natural Resources accessible at  https://anrcatalog.ucanr.edu/pdf/8100.pdf

and the book titled Frost Protection: Fundamentals Practice and Economics, by Richard Snyder, UCD Dept. of Land, Air and Water Resources, and J. Paulo de Melo, which can be downloaded for free from the United Nations Food and Agriculture Organization website at http://www.fao.org/docrep/008/y7223e/y7223e00.htm#Contents.

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