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A hard freeze can put an end to an otherwise nice cool-season garden. Using mulch and protective covers and creating a PVC pipe box are some ways to help plants through a freeze.

Old sheets or lightweight tarp materials can cover plants overnight.

Our winters are usually but a brief interruption in our long growing season. However, a hard freeze can put an end to an otherwise nice cool-season garden.

There are numerous marginally hardy plants such as Brazilian sky flower (Duranta), fig trees, yellow bells (Tecoma stans), Pride of Barbados, Satsuma orange, and kumquat that can make it through the winter if we can just get them through a hard freeze or two.

Last February, we were fortunate to have a snow cover that saved a lot of annuals and perennials, but snow isn’t something we can count on most years. Here are some steps to take to protect semi-hardy plants on nights when the temperature drops into the mid-to-low 20s.

A thick layer of spent hay, compost or shredded leaves over the soil surface can help protect the base of a tender plant during a brief winter cold snap.

A ring of wire mesh fencing encircling a perennial plant and filled with shredded leaves is an alternative technique. Then in spring, the wire is removed and the leaves are spread around the plant’s area as a nice surface mulch.

Most people have access to old sheets or lightweight tarp materials to cover plants overnight. Frost blanket fabric is available in some garden centers to use in the same way. These dense spunbound polyester fabrics provide a few degrees of protection by holding the rising warmth from the soil beneath them and around underlying plants.

It is best to remove sheets, tarps and rowcover fabric during the day to allow the sun to warm the soil. If another freezing night will follow, cover them again in late afternoon or early evening.

Prize plants that lack much cold hardiness such as small citrus trees can be covered for some protection, provided that the cover extends to the ground so it will trap rising soil heat. To simply wrap a plant like a “landscape lollipop” will do little good, and in fact blocks rising soil heat from reaching the plants.

Sections of PVC pipe can be used to make a box or frame around a tender shrub or young tree. Cover the frame with inexpensive clear plastic to make a mini greenhouse. I use a 6 mil plastic which is readily available in most home supply stores. It will last through one winter season.

This PVC box needs to be anchored to hold it down when a “blue norther” comes blasting through. This is also where plastic helps since it prevents the air beneath the cover from being displaced by the colder outside air.

The PVC framed box alone can help on a moderately cold night. For a hard freeze, you may want to add a source of heat inside the cover.

Light bulbs (100 watts or more) can provide a few degrees more protection. I prefer to use flood lights with a clamp and aluminum shield because they are easy to attach and direct downward. Keep the lights low near the ground since their heat will rise into the plant canopy, and don’t place them too close to the plant trunk or branches.

Electricity and dried grass and mulch can be a recipe for disaster. Check cords for bare areas, make sure plugs are protected from rain, and don’t allow the hot bulbs to contact dried flammable plant matter or plastic.

Robert “Skip” Richter is the Texas A&M AgriLife Extension horticulture agent for Brazos County. For local gardening information and events, visit brazosmg.com. Gardening questions? Call Skip at 823-0129 or email rrichter@ag.tamu.edu.

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A hard freeze can put an end to an otherwise nice cool-season garden. Using mulch and protective covers and creating a PVC pipe box are some ways to help plants through a freeze.

Old sheets or lightweight tarp materials can cover plants overnight.

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