Recently the River Parishes saw temperatures drop into the upper 20s, new record lows for us in November. This event followed record-setting October heat, which didn’t help things. Plants were nowhere near dormant, so they suffered worse than they would have if the freeze had waited until January. Flowers and fruit are especially susceptible to cold, which was bad news for mirliton and other plants that failed to finish early enough.

Though we probably won’t have such a shocking freeze again any time soon, winter is coming. I get a lot of questions about protecting plants, usually after the freeze has passed. Let’s go over some tips to protect plants when the next freeze comes.

One method of protecting plants is to create a micro-environment a crucial few degrees warmer than the surrounding air. If your plant is in a pot and the freeze is not too severe, simply moving it out of the wind and up against your house may suffice. A screened-in porch or a garage provides great protection.

And what about in-ground plants? You can simply pile a thick mat of mulch over the plant, or at least around its base. Uncover the plant once the freeze is done so it can get light and dry off.

For large plants, including small trees, it’s best to use a wind-proof sheet like a tarp to cover the plant. If possible, use a frame of some kind to keep the material from touching the plant. The sheet will be nearly as cold as the air surrounding it, and the plant could be damaged where it touches. It’s critical to seal the plant off thoroughly. Be sure the tarp touches the ground, and weigh down the edges with soil, bricks, or whatever’s handy.

Using clear plastic is also effective if you cover the plant and let the greenhouse effect warm it during the day prior to the freeze. But be sure and vent this system the next day if it’s warm and sunny, as is often the case in Louisiana.

Another way to use solar power is to get a large bucket or barrel full of water and paint it black (like The Rolling Stones suggest). Placed near a tree, it’ll absorb sunny warmth. As the sun goes down, cover it with a tarp / tent as described above. The warmer water will give off a little heat during the night.

To protect or not to protect is the other question. At a given temperature, this decision can usually be made depending on the species’ cold tolerance. The LSU Ag Center has a list of several common tolerances; contact me as outlined in the last paragraph if you’d like a copy.

Tropicals, of course, will not be very cold-tolerant. Anything below 32 degrees can threaten them. But most woody perennials and winter vegetables will not need to be covered at all in a typical winter. Lettuce may sustain a little damage, but most all other vegetables will bounce back, even if they look wilted first thing in the morning.

Besides low temperature and plant species, also consider if the plans are “hardened-off.” If plants have been exposed to low temperatures, they shouldn’t be quite as sensitive in the next freeze.

 

If you want to know more about gardening, landscaping, or anything else horticultural, contact the St. John, St. James, & St. Charles Parishes County Agent André Brock at abrock@agcenter.lsu.edu. Also, the LSU Ag Center’s website can be accessed at www.lsuagcenter.com with lots of user-friendly information, including this article.