Young citrus trees are generally more sensitive to the cold than fully mature trees. Newly planted citrus trees, as well as those that have been in the ground for less than five years, may need a little more protection. Watering them deeply before a cold snap helps to prevent frost damage. Wet soil radiates more ground heat than dry soil. Keeping the area beneath the tree free of weeds and other debris also helps natural ground heat to radiate and protect the tree.
The older a tree, the more cold tolerant it is. All citrus trees also become “hardened off” to the cold as they are gradually exposed to cold temperatures. A few warm days in a row, however, can spoil the “hardening off” effect.
Fertilizing citrus in the late summer also helps to impart some cold protection, as healthy trees recover from a frost much more readily. Be careful to not over-fertilize, though, as this can actually make a tree more tender heading into the winter. Dark green, healthy trees will have a better time weathering the cold.
Certain types of citrus trees are hardier than others in the chilly weather. Satsumas are hardy up to temperatures of 25 degrees. Lemons limes, and grapefruit are less cold tolerant, and need additional protection in the 28-30 degree range and below. It's a good idea to harvest all of your citrus fruit before a hard freeze. It takes 10 hours of temperatures in the low 20s to ruin fruit.
If a hard freeze is on the way, several things can help to protect young citrus trees from cold damage. Wrap the trunk in cloth or bubble wrap. Use tarps, old blankets or plastic sheeting to wrap the tree. Decorating the tree with the non-LED Christmas lights also helps by generating a bit of heat in the foliage. Be sure to remove the cover as soon as the sun comes up to avoid cooking the tree accidentally. Plastic sheeting and tarps work like a greenhouse and can trap too much heat.
For more information, check the LSU AgCenter website. LSU AgCenter publication No. 1234, Louisiana Home Citrus Production, has helpful information for home citrus growers. This publication is available as a free PDF or a color printed booklet for $10.00 from www.lsuagcenter.com. To sign up for the GNO Gardening newsletter, email GNOGardening@agcenter.lsu.edu.
Question: I have Bermuda grass taking over sections of my St. Augustine lawn. What can I do, short of re-sodding to get rid of it? — David
Answer: Bermuda grass can be controlled by encouraging the St. Augustine grass to outcompete it. Increase your watering times if you are using irrigation. Raise the height of your mower deck to at least 3-3.5 inches to help encourage the St. Augustine to grow thickly. Bermuda thrives in close cut lawns, so raising the mowing height discourages it. Use a weed and feed product that contains a pre-emergent herbicide this spring, which will discourage germination of Bermuda grass seed while simultaneously fertilizing the St. Augustine. If all of these tricks fail, use a nonselective herbicide on the Bermuda and dig out the rhizomes. Re-sod the area with St. Augustine.
Joe Willis and Anna Timmerman are LSU AgCenter extension agents. Questions? Email firstname.lastname@example.org.