What to do After the Freeze, DECEMBER 2010

Interesting weather, isn’t it? It’s unusual to have such cold in December. And because that is different than what our typical experience is, it requires a more thoughtful approach to damage management. But don’t panic. If you simply consider each aspect of plant care within the context of winter, you should be able to manage this with ease.

The basic aspects of plant care are:

1) Exposure to light, temperature and wind;

2) Hydration (or water) needs;

3) Sanitation;

4) Mechanical intervention (repotting, planting, pruning etc.)

5) Nutrition & fertilization; and,

6) Scouting for pests & disease.

Now some of you are thinking, “That’s a long list of ‘Basics’!” But it’s not as troublesome or time-consuming as you may think. Let’s look at each area.

Exposure & Hydration. By now, the effects of exposure to cold will be evident on many plants. You may see discoloration, or a mushy wetness. Sometimes cold damage appears as a silvery-grey cast to the foliage. Take note of the patterns of damage on plants. This will afford you some insight into where the coldest air settles in your microclimate of a yard. You should see a pattern on the north and west sides of plants directly exposed. You may see other patterns on plants that have some protection from other plants or buildings. I have a Costus barbatus along the south side of a porch. While you might think the south side would be protected, the porch roof slopes up steeply to the north. I can see by the damage pattern on the top leaves of this plant that the cold air just flowed down that roof, from north to south and puddled onto my plant much like water would have.

With most cold fronts there is a period of blustery winds just before the cold moves in.  This most recent cold spell was preceded by 36 hours of windy weather. Wind causes plant moisture to evaporate. As a result, your plants are DRY. But you don’t want to water during the cold temperatures. When day-time temperatures stay below 70 degrees Fahrenheit, plants’ metabolism slows down, with a resulting decrease in water uptake. You could “drown the roots” if you water in those cooler temperatures. But once “turned on” by the 70-degree-switch, they will be very thirsty! Water at the roots (avoid wetting the foliage-see Sanitation) and add SuperThrive (do not fertilize-see Nutrition).

Sanitation & Mechanical Intervention. If you have damage to your bedding plants (impatiens, begonias, etc) you will need to cut them back to below the damage and feed with the slow release Leonard’s 14-14-14. You’ll be amazed at how quickly they will snap back and look lovely again. For your woodier shrubs, trees and palms the focus of you efforts will be to get the plants cleaned up.

There is some truth behind the saying “Cleanliness is next to Godliness”. Nipping disease in the bud is your immediate priority. Your plants are stressed from the physical demands of cold weather. Damage to the leaves impairs the plant’s ability to block bacteria and fungi from setting up shop. These factors make the plant susceptible to infection. This is particularly a problem in that the damaged leaves on the plant are decaying tourines of microbial soup!

Get that stuff out of there. Use a shrub rake to remove fallen debris, and snip the rotting foliage off at a point well below the decay and just above a leaf node. Be careful not to transfer disease on your clippers. Make your cut through healthy flesh. Do not prune any more than is necessary to remove dead foliage (pruning stimulates a flush of new growth).  This rotting material has to go because as rain or sprinkler water hits the diseased leaf, then splashes onto an area of healthy foliage it carries the infection with it. Take measures to limit opportunities for disease to get a foot-hold. Water early in the day so that leaves are dry during the night. To prevent disease, treat plants with SuperThrive or KeyPlex to boost immunity, and Serenade a beneficial microbe that is very effective in killing off the not-so-beneficial microbes. Palms can benefit from an application of fungicide whether or not symptoms of fungus are apparent. First check for viability by pulling on the leaf that is emerging from the top. If this pulls out, your palm is dead. If not, clean it up and treat with Liquid Copper.

The clearing of dead leaves is an important activity in a large part because it is an activity! I find a lot of folks too eager to cut back or pull out damaged plants. Just be patient. If you must do something then rake up the leaves. If you haven’t mulched this fall, then mulch. This will protect the roots from future cold snaps and add a clean layer of substrate under the plant. DO NOT do any heavy pruning! You will cause of flush of tender young growth that will be a terrible exposure for the plant in the event of another salvo of cold. Save the heavy pruning for spring, after the “last frost date”. Remember that phrase from your northern gardening experience? I hardly ever have to use it here!

Nutrition & Fertilization. Now is not the time for a general feeding. Hopefully, you fed in the fall. We recommend a prune & feed sometime between Labor Day & Columbus Day. This way the plant can build its nutrition reserves before metabolism (and rate of uptake) slow. Those reserves come in handy once we get higher night time temperatures and spring flush takes off. Sometimes winter cold damage only becomes apparent at in spring, when nutrition demand (spurred by rapid growth) outstrips the combined nutrition uptake and reserve. If you didn’t feed in the fall, you could feed now with a liquid product, such as Jack’s Classic or Southern Ag’s Liquid Minors. These products can be absorbed through the plant’s leaves and stems. I recommend this particularly if you begin to see a flush of new growth as we now warm up. Because plant metabolism slows in cooler temperatures, granular feed that requires breakdown and root absorption are of little help now. It will be critical, however, that you do use a slow release, complete granular fertilizer at the break of spring (Valentine’s Day to the Ides of March) and again at the start of the summer rains (Mother’s Day to Father’s Day). For this we suggest Leonard’s Ornamental Mix: Palm & Shrub feed. It’s a grower’s product distributed by Harrell’s Corporation. Marvin trusts this product and finds the capsules break down in a more consistent manner regardless of how hot or wet it is. Remember to feed any plants within 30 -50 feet of a palm with fertilizer labeled for palms.

Scouting. As I noted in the discussion of sanitation above, bacterial & fungal disease are the greatest problem now. These can be foliar (on the leaves), on the flowers, involve the stem, or affect the roots. They appear as grey to black or brown wet patches on leaves or at the base of the stem (where green flesh has contact with soil). In some cases you will see a little “fuzz” or grey mold. This is often seen on flowers, sometimes on the leaf surface. These “molds” (most commonly botrytis, downy & powdery mildew) are spread by spores, the fungus version of seeds. So as you are clearing plants of this debris, wear disposable gloves and grasp the entire mass of debris within your closed palm.  This prevents the spores from becoming airborne and lighting on healthy tissue nearby. The good news is that cooler weather will decrease the populations of active pests. The time to be alert for those forces of evil will be with the new flush of growth.

That doesn’t stop the perennial pest of Florida, the mosquito. These cool evenings make for great al fresco living. But you may find that with cuts in County services, mosquito populations are a bit higher this year. We have several great products that are great for controlling these buggers. I love my Thermacell Lantern. It provides a room-sized bubble of mosquito protection that I can take along with me as I move around the yard. For more consistent protection, CedarCide granules repel gnats, flies, fleas and mosquitoes with natural ingredients like cedar flakes, clove oil and rosemary. Effective, safe and it smells great!

So the truth is that after the freeze you need do nothing more than you do any other time. Simply always remember that a plant is a living organism, responding to an ever-changing environment. We can anticipate a specific response to the cold environment. If you keep that in mind, you will find you really know more than you think!