Sub-Freezing Temps Are Coming—Here’s the Right Way to Wrap Plants

When a late (or early) freeze is in the forecast, the best way to protect vulnerable plants is to wrap them. Covering plants with frost cloth, burlap, or even an old sheet, traps heat that’s naturally radiating from the soil, keeping the air around the plants a few degrees warmer than the surrounding air. While wrapping your plants can save them from Old Man Winter, doing it the wrong way can leave them vulnerable to the cold and even do more harm than good. Use the right methods when wrapping your plants is key to protecting them from frost damage.

Related: Hard Freeze to Hit the Mid-Atlantic and South—Protect Spring Blooms

Step 1: Water the Plants

Well hydrated plants are more resilient to ice crystal formation than plants that are dehydrated. Wet soil also absorbs heat more than dry soil while also retaining it longer in freezing temperatures, according to the Mississippi State University Extension. Water your plants in the afternoon before the hard freeze to give the soil time to absorb the sun’s heat. 

Step 2: Use the Right Material

Using the right material is crucial to protecting your plants from the cold without damaging them. Use materials that breathe. Old sheets, burlap, or commercial frost blankets trap heat while allowing moisture to escape. Avoid using plastic, which traps moisture inside that can freeze. Since plastic is a poor insulate, it can also cause contact damage if its resting on the foliage.

If you’re dealing with extreme cold, professional grade heavy-duty frost cloth offers the most protection as it can increase temperatures around the plant by as much as 10°F. This compares to bed sheets, which can increase temperatures by around 3°F and lighter frost blankets that can add around 6°F. 

Step 3: Cover the Plant

Cover the plant with your chosen material. The cover should drape over the plant without touching its foliage. Use stakes to create a frame that prevents the cover material from touching the plant.

Step 4: Create a Sealed Dome

Many homeowners focus on the plant's foliage and ignore the ground by wrapping around the top of the plant and tying the cover tight around the trunk. This method won't trap heat that’s radiating from the soil.

According to the NC State Extension, the cover should extend all the way to the ground around the entire plant, hence creating a sealed “dome” of warmer air. Use landscaping pins or garden staples to secure the edges to the ground or way the material down with heavy objects like bricks or sandbags to prevent wind from lifting up the cover. 

Step 4: Remove the Cover As Soon As Possible

While wrapping plants can protect them from a hard frost, covers aren’t good for the long term health of the plant. If the sun comes out while the plants are covered, it can cause temperatures inside the “dome” to spike, cooking it or causing the plant to wake up too quickly. Remove the cover as soon as temperatures rise above freezing the next morning then replace them in the evening if temperatures are forecasted to drop below freezing again. 

FAQs

How cold is too cold for wrapping?

Once temperatures drop below 25°F for more than a few hours, wrapping loses its effectiveness. At these temperatures, the heat released by the soil isn’t enough to keep temperature around the plant above freezing. If temperatures are forecasted to drop into the low 20s, you’ll need to add a heat source in the “dome,” such as a string of indecent Christmas lights, to keep temperatures above freezing.