I’ve been watching our local weather forecast and it looks like we are in for some 30-something degree weather! With overnight lows dipping into the lower 30s in the coming days, many East Texans are wondering whether they should rush out and cover every plant they own. But according to Texas A&M AgriLife Extension horticulture specialists, not every cold snap is the same—and not every plant needs saving.
A light frost is typically 30–32°F for only a short period before sunrise. This is part of a normal fall transition and, for our part of the world, happens in mid-November on average. A hard freeze, 28°F or below for several hours, is what causes serious injury. Knowing the difference can save you a lot of effort, and in many cases, unnecessary worry.
So, let’s dive in- What is at risk at 30°F? Warm-season annuals are the first to show damage. Warm season herbs such as basil, and flowers such as coleus, sweet potato vine, and anything tropical will likely turn to mush after a frost. Summer vegetables such as tomatoes and peppers—if you still have them hanging on—will be also ruined once frost hits the foliage.
Warm-season turf like St. Augustine or Bermuda is already going dormant this time of year, and AgriLife turf specialists point out that a single frost is not harmful to the grass itself. San Augustine grass, our favorite lawn grass, largely stops growing when temperatures stay around 55° F.
Bermuda and Bahia grass pastures will stop growing as well. Bermuda grass typically stops when soil temps consistently reach 60 F. Bahia will continue to grow (every so slightly) until temps are in the 50° F range.
But in your fall planted vegetable or ornamental gardens, you may have several plants that will push through and never notice the coming 30° temperatures. AgriLife horticulture guidance notes that broccoli, cabbage, kale, collards, carrots, lettuce, beets, turnips, pansies, violas, snapdragons, and dusty miller all tolerate a light frost and often improve in color and flavor because of it.
So, before you drag out the bedsheets to cover your plants, it’s worth deciding what truly needs protection. Plants don’t die because the air hit 31°F—they die because heat radiates out of the soil into the night air. Clear, wind-still nights are the most dangerous. Texas A&M AgriLife Extension recommends using frost cloth or lightweight fabric—not plastic—to trap heat rising from the ground. Covers should reach all the way to the soil and be weighted at the edges. A cover floating above a plant won’t help much.
Just as important, covers must come off the next morning. Leaving them on during a sunny day can trap too much heat and cause even more damage.
Don’t have a frost cloth…or don’t want to bother with putting it on? Watering before a frost helps. Many folks are surprised to learn that slightly moist soil protects plants. Moist ground absorbs and holds heat better than dry ground. Again, research from AgriLife and other universities say watering the day before a freeze can help insulate plant roots. Once frost arrives, though, watering won’t “save” already-damaged leaves.
Container plants are the most at risk, since exposed pots lose heat quickly. I remember foolishly claiming to a local nursery owner how my figs all came back from the very cold weather we had in February 2021. My figs were in the soil and mulched well. The nurseries figs were all in pots where all sides were exposed to the freezing temps.
If you have potted plants that won’t take a frost, move your containers into the garage or under a porch. If they must stay outside, cluster them together near a house wall to take advantage of stored heat, and wrap the pot—not just the foliage.
Also, don’t prune after a frost. This is one of the more frequent mistakes. Frost-damaged leaves look ugly, but experts caution against pruning right away. Damaged foliage can actually insulate the plant from the next freeze. Wait until late winter or early spring to remove dead material.
A practical plan for this coming cold weather is to protect tropical plants, summer vegetables, and tender annual flowers. If you have container plants that you want to save, move them “inside” or wrap them well. The day before the cold weather arrives, water the soil to add a measure of ‘heat’ to the ground around it.
I do have some woven frost-protection sheets that an aged gardener gifted me long ago. I don’t know if I’ll make this, potential, first frost a big deal. Maybe I’ll save some potted plants that I want to last a little longer and let the rest go.
