Last week’s freezes were not nice to many of our landscape plants, especially the tropical ones of which we are so fond.
Many of the palms, cycads (sago palm), herbaceous plants like lantana and tropical-foliage plants that find their way into outdoor landscapes and, of course, citrus were injured to varying degrees by the chill. Most of these plants will start showing injury once they thaw out.
Palm fronds may have turned khaki at the leaf tips and margins or may have browned out completely. Sago will show small sections in individual leaflets about an inch long that first turn lighter green and then turn yellow to tan. On a single multiple-leader sago, the parent leaves may be unaffected while the “pups” may show extensive injury to the fronds. Lantana has turned entirely khaki to tan if severely injured. Citrus may show freeze injury to leaves that remain attached; more frequently, the plant will defoliate.
There is a natural tendency to want to rush out and prune off or prune back the injured tissue, if not to help the plant, at least to improve the aesthetics of the landscape. Freeze-injured plants just are not pretty, and we do not like looking at them.
Try to resist the urge to go out cutting back injured plant tissue. We are not out of the woods yet with freezes. The average frost-free date for the Richmond Hill area is Feb. 20, and the average frost-free date for the Pembroke area is not until March 5. If we prune now and get another round of freezes, the plants easily could be injured even more than if they were left untouched. Opening up fresh wounds to the air can allow entry to fungi and bacteria that could not get past the waxy cuticle and epidermis that exists even on freeze-injured plants. Cutting back to healthy tissue just exposes the plant to risk of infection and desiccation at a time when it is not actively able to close wounds and staunch the bleeding from cut water vessels.
If a succeeding freeze catches a plant in this condition, it likely will suffer more injury than if it had those injured tissues still in place as a first line of defense. Especially on citrus, please wait until we are well past freeze chances. Even wait until new growth resumes next season before cutting off dead twigs and branches. What looks dead might not be. Give the tree a chance to show you what it can do before you start wounding it.
There are exceptions to every rule. If your sago was injured badly but you were thinking of harvesting pups, this would be an ideal time to undertake that project.
First, cut off all the fronds on the pup. Next, expose the area where the pup comes out of the stem of the parent plant. If this means excavating soil from around the pup, do so. If there is soil on or near the joint, wash the soil away with a strong jet of garden hose water and let the area thoroughly dry before proceeding. Cut the pup from the parent stem with a sharp, flat shovel. Let the wound on the parent plant callus over for at least seven days before allowing soil to come into contact with the wound. Set the pup in a cool, dry place out of the sun for a week to let it callus over its wound as well. A garage is a great holding area for pup recovery. Then you can plant the pups in the landscape or in pots.
The worst thing you can do to cold-injured plants is hit them with nitrogen fertilizer. Plants in trauma need a chance to stabilize and seal off injured tissues. Nitrogen forces them to waste energy growing leaves and getting succulent — just in time for the next freeze to kill that new tissue and multiply the plant’s problems. It usually is best on cold-injured woody plants to let the new spring growth harden off before applying fertilizer the first spring after the freeze occurred.
There always is something to do in the garden. For those who have not done so, inspect your trees, shrubs and even herbaceous perennials for scale insects. If you find them, a dormant oil spray now will suffocate the little buggers before new growth starts in spring. The spray has to hit the bug and cover it, so none of this drive-by spraying will do. The plant has to be thoroughly covered with dormant oil spray, top to bottom, stem to twig and on the underside of leaves and twigs as well as the tops.