Cold Damage Identification and What to DO about it

The past month or so, I have made numerous blog postings about bringing in your plants and protecting them from the Winter weather. If you missed either of these postings, you can read it HERE and HERE .
Today I am going to talk to the people that, for one reason or another, didn't bring their plants in or try to protect them. They may have missed the weather report, forgot about their plants, or didn't want to take the time to do it and now their significant other is upset because the plant looks dead. There may be hope!
You will need to ask and answer a couple of questions: How cold was the temperature? How long was the plant exposed? What was the health of the plant before the damage?
First, let's take a quick look at what cold weather is and how it can affect plants. I know, duh, it's cold, they freeze! Well, just follow me for a minute.
The sun warms the soil surface during the day; the heat is then radiated into the cool atmosphere during the night. The coldest temperatures occur about daybreak.
Clouds at night can absorb and reflect heat back to the earth.
Calm, clear nights pose the greatest danger of frost since there is no wind to mix the ascending warm air with the descending cold air, and no clouds to radiate heat back to the soil.
Cold air settles downward, flowing like water,to the lowest point. Hot air rises.
The effects of temperature vary with plant species, stage of growth, age, general health and water content. Young, actively growing, flowering, and/or dehydrated plants tend to be most vulnerable.
Freezing temperatures damage plants by rupturing plant cells as ice crystals form and rapid changes in temperatures occur. Evergreen plants can suffer damage from blowing Winter winds and dry out when water is unavailable from ground that is frozen. Chilling injury can occur to many tropical plants although temperatures do not drop below 32 degrees.
The signs of cold damage can be confusing, since some damage may not be evident until months later. Leaves and tender shoots subjected to freezing temperatures or chilling damage appear water soaked and wilted. These tissues will usually turn black within a few hours or days. The tips of narrow-leaved evergreens, such as junipers, may turn uniformly brown. Broad-leaved evergreens, such as hollies, often have leaf burn along their edges. Less flowering is common during the following season.
One of the main things to remember is Do NOT prune frost-damaged, woody growth until the plant begins growing in the Spring. Pruning might stimulate new growth which would be vulnerable to late frosts. The frost damaged leaves and stems will continue to help trap warm air within the canopy. This is especially true in very large leaf type plants, such as Bananas. In addition, the damage is often not nearly as bad as it initially looked, new growth may come out of tissue that you thought was dead. Once the new growth starts in the Spring, you can prune out the dead wood.
A large, deep, crack running up and down the trunk of a tree or large shrub is known as a frost crack. The crack is usually on the South or Southwest side of the trunk, but can occur on any side. Young trees or older trees with smooth bark are the most susceptible.
Frost cracks occur when the sun warms the trunk in the Winter, causing tissues to rapidly expand or when clouds or buildings block the sun. At sunset the temperature of the trunk drops quickly to that of the surrounding air, and the trunk contracts. The outer part of the trunk cools and contracts faster than the inner tissues. This difference in contraction rates can cause the outer trunk to crack. You can usually eliminate this problem by wrapping the trunks with burlap or some other type of protection, not plastic, it needs to breathe. Start at the ground and work your way up to the first branch. Prevention is important, once the crack occurs, there is not much that can be done. Such frost cracks often close and callus over during the Summer, only to reopen in following Winters. This callusing and recracking may lead to the formation of large "frost ribs" on the side of affected trees. Something else to keep in mind, insects like to find places to hide and a large split open trunk is basically a "We'll keep the light on for you" sign. You could be looking at a major infestation. Frost cracks in trees are also ideal sites for the entrance of wood decaying organisms.
Desiccation, or drying out, is a particular problem on evergreen plants. This occurs when water is leaving the plant faster than it is being taken into the plant. During the Winter months desiccation can occur if the ground is frozen beyond the depth of the root system. If the Fall has been dry, there may not be enough ground moisture available for the plant. Water loss is greatest during windy, sunny conditions. This type of injury appears as discolored or burned evergreen needles or leaves.
After a killing cold some plants may be frozen back to the ground but lower buds and roots often survive. It can take these plants months to begin growth. Give them at least the Spring months to show signs of growth. I had a Clethera that did not regrow until Summer. I had just about given up on it but it showed me how persistent plants can be.
Okay, you have this plant that has lost all its leaves, looks naked and you are figuring it is a goner. Take a look at the bark or stem, is it black, shriveled or separated from the trunk? It’s most likely beyond help if it is. Don’t look just at the top but down at the base.
Next start high and scrape a small section of the bark. If you find brown at all keep moving lower until you find green, believe me you’ll know when you find it.
When you find an area of green, cut off everything above it, on that stem or branch. When you get done going over this you may have a plant that stands a chance of coming back. This really needs to wait until Spring though.
Remember, not only was the foliage, branches and stems exposed to the cold, so were the roots. No matter how hard you try the plant may not survive. The root damage may be so severe that you’ll be fighting an uphill battle.
As much as you may love your plant, you must be realistic, It may be too far gone!
I get teased all the time about my infatuation with what the weather is doing, what it is going to do and what it has done in the past. The best remedy is to keep your eyes on the weather, bring your plants in before the cold hits, and to grow things that are suited for your climate zone.
I hope everybody has a Very Merry Christmas!
Happy Growing!
Darren

Tis the Season to be planting!

One thing that I have been trying to get some traction with when I talk to clients about gardening is "Fall is the best time to plant. The looks I often get are amazing. You would think I just told them that a Cactus will live in Antarctica. It is true however, Fall is a GREAT time to be gardening!
Mother Nature herself tells us Fall is the time to plant. Many plants flourish all Summer long, then go to seed. The seeds are dispersed at the end of the growing season or in the Fall and get "planted". There are many seeds that need a Winter stratification to produce a new plant next Spring. Stratification is a means of Pre-treating seeds (cold stratification) as a simple measure you can take which will break a seed's dormancy. In simple terms, it needs cold to take a nap and grow next year.
In the Fall, you (theoretically) have more time to get the work done. First of all, there is a longer period of time and far more "good weather days" for planting in the Fall than during the tricky weather of Spring. Late frosts and crazy storms come to mind. Then there is the aspect of trying to clean up after Winter's mess. I don't know about you, but I seem to have much more work to do in the Spring than I do after the Summer battle. Less to clean up, the more time to plant.
The soil is warmer in the Fall than in Spring, and there's still time for roots to get established before the cold weather sets in. Fall officially begins with the Autumn Equinox in late September, but Fall weather varies considerably from one part of the country to the next. Basically, the ideal period for Fall planting is roughly six weeks before the first hard frost. And in northern areas of the country, the ideal planting period might even be late summer. In general, the window of opportunity for most folks is during September and October. Roots can grow in soil as cold as 40 degrees, and soil remains warm long after the air temperature drops. This is even more prevalent in the Northern areas, where the ground actually freezes. Plus, there is less heat stress on the leaves and stems and such, the roots can have all the attention. Just as a side note here, when you do plant a tree or shrub in the Fall, Do not fertilize it. This could spur new foliage growth that will be damaged in the cold of Winter, weakening the plant. Wait until Spring to feed it. There is some argument as to whether you should give it some slow release before it takes a long Winters nap, that way it wakes up with food already to go. I for one figure it is just better to not take a chance.
There are plants that can and should be divided in the Fall. Hostas, Iris, Cone Flowers, and for the folks up North, Tulips, Crocus and such come to mind. Spring flowering bulbs are of course the one thing everybody does think about planting in the Fall. So if you plant them in the Fall, why not divide them then? They need the cold to flower for you next year too. Other bulbs to plant now, Garlic and Onions. Perennials also need dividing to stay fresh and productive, it should be done every three years or so, why wait for Spring?
Here in the South, Lettuce, Collards, Mustard Greens and Cabbage are going into the ground now. You have to have those greens ready for "Hoppin' Johns" on New Years Day.
If all of these reasons are not good enough, how about this one. Go to any big box store or garden center.....they are probably having a great sale on trees, shrubs and perennials.....which reminds me, I need to go shopping!
Happy Growing!
Darren