ICE AND SNOW
Although winter can be a welcome respite from garden chores it can also cause some plant anxiety. Watching the hard frosts turn plants brown/black and perennials to mush can add to that feeling of winter “ugh”.
Even mild winters can cause injury to plants. This damage many times doesn’t get noticed until you have come out of hibernation and taken a good look around. Fluctuating temperatures in the 50’s-60°F then a quick dive below freezing takes a toll on many evergreen leaf/needle tips. Concern really mounts when days with heavy wet snow and icy rain occur. During a heavy snowfall gardeners can suit up and march around outside with a broom handle to dislodge the snow from weighed down branches. This may be a great activity for kids, if you have any handy. Although a reminder not to whack the shrub/tree endlessly may be needed!
An Icy Burden
Ice can be tricky depending on the accumulation; a thick icy coating can cause branch splitting and breakage. Add wind to that and some serious damage can occur. Breakages at eye level can be easy to spot but mostly gardeners will not know of winter damage until spring is well advanced.
Hardy Hibiscus and a Juniper with a coating of ice.
Recently, my Pyrocantha x‘Mohave’ suffered a few breakages during an icy weather event. In two different places the upward branches split at a “Y” joint and the weight of the ice on the branches caused the split to tear further down the main line. I have pruned the split out from the one main branch. On the other break I pruned out just one side of the “Y” split and am going to watch it and see if it will heal over. An open wound like that is an invitation to pests but I am going to try it. If it is looking terrible I will prune it back. My Pyrocantha looks like it has strange gaps in the middle of it but I can deal with that for one summer.
WHAT TO LOOK FOR:
Here are some symptoms of winter injury- leaf or needle tip browning/burning/bronzing; leaf marginal burning, wilted looking leaves that eventually turn brown. Boxwoods, Holly trees, Arborvitae, Rhododendron and Camellias are plants that come to mind when I think of winter damage.
Unless obvious, gardeners will have to wait until spring to accurately access the damage from severe snaps of cold weather. Many times bronzed foliage can be pruned back and new growth will emerge. If you have Arborvitae, Boxwood, Junipers or Yews and some damage has occurred, prune out the dead, damaged or dying material. If you have Pine, Spruce or Firs with some browning on the needles, often no pruning will be needed. New growth will emerge from the tips.
SKIP THE FUSSY PLANTS!
One way to avoid some of the landscape anxiety that may happen with consistent freezing temperature is to make sure from the beginning that you are installed trees/shrubs/perennials that are appropriate to your hardiness zone. Not sure what that is? Here is a great link for free info.
The USDA has already done the work of figuring out which plants will be most successful for where you live. For example you may live in Zone 5(parts of New England and Mid-West Corn belt) and love the tropicals! The Cannas, Dahlias, Bougainvillea, and Citrus just to name a few, but they will not survive the winter. Either gardeners treat them as annuals or they reside in pots and are brought inside(greenhouse, garage, coldframe) every year. For me in Zone 7B, I have palms in large pots I shelter in my shed (it has a sliding door facing south) every winter. The rest of my landscape I chose plants that will survive and thrive in my zone. I don’t want the extra work of coddling a lot of tender plants.
PLANT CELLS
Plants do have an awesome built in system that helps them to withstand cold temperatures. This is where my horticultural nerdiness flairs up! In the fall, plants go through the process of cold hardening. Responding to the declining temps, the cells of the plant will begin accumulating sugars and these high concentrations of sugar act like an antifreeze for the plant cell. This usually works great but there are times when the water in the cells will freeze and the cell membranes are ruptured and that is when gardeners see more serious wounds on the plants in their landscape.
THREE WINTER INJURIES
FROST CRACK
The dramatic winter injuries that happen to trees and shrubs are frost crack, desiccation and sunscald. One sounds like a geological formation and the others a skin condition! A frost crack will happen on smooth barked trees (mostly) and on the south facing side of the trunk. Here’s what happens-with low temps, the tree tissues freeze and then there is a warm-up; the southern side of the trunk may thaw out some and soften add another freeze and CRACK! There is pressure built up between the frozen tissues and the outer softened tissues and it causes a vertical crack or split to form in bark.
DESSICATION
It is amazing but a tree or shrub can dry out in the winter. That is what desiccation means; to dry out or the process of moisture loss. Even in winter on a sunny or windy day trees and shrubs are transpiring. Water vapor is being lost through the leaves/needles. But what about all that snow and ice and slush? It is important to remember that those tiny feeder roots of trees/shrubs are in the top three inches of soil. If the soil is frozen the plant can’t take up any water to replace what it has transpired. So it will begin to dry out and leaves/needles will droop and brown.
SUNSCALD
Sunscald is another issue that will occur on the bark of certain smooth barked trees. Do you ever remember seeing tree trunks painted with white paint? Many times gardeners would try this to attempt to avoid sunscald. The white paint would reflect light and keep the tree from warming up and budding out too soon. Again this injury occurs on the south or southwest side of the tree. On a warmish day with light bouncing off the snow or a nearby building or sidewalk, the tissues on the southern side will warm and soften and then freezing overnight temps is all it needs for the tree to react with softened depression which becomes an ugly and weepy canker. Young trees of cherry, maple, crabapple, eastern white pine, aspen and mountain ash. The good news is that many times the tree can heal this wound.
SHORT ANSWER FOR TREATING THESE INJURIES
Many times a tree can heal from these injuries. It will build and form a callus over these wounds. You will have to check on these trees and shrubs periodically. As they recover they are vulnerable to secondary issues, attacks by insect pest or fungus/bacteria. If there is severe dieback, pruning out the dead material in the spring will need to happen and then stand back and see how terrible it looks! A small shrub can be transplanted to an area of your yard where it can recover and you don’t have to walk past it everyday. If it is large, misshapen from damage and an eyesore it is time to yank it, chop it, dig it out and start with something else.
The links below are just an example of the free, science based info that our University Agricultural/Horticultural extension offices provide. There is an university extension service in every state! Don’t miss out on reliable and free info not only on winter injuries but a variety of topics.
TRYING TO FIGURE IT OUT AND A TIP TO HELP TRACK CHORES/WEATHER EVENTS
But is all that brown foliage caused by cold weather damage? Although I always prefer an “easy” button, determining the cause of browning or die back on tree/shrubs can be especially frustrating. Many times the damage evident in April or May might have begun the summer/fall prior. And who can remember the weather or what they did last summer?
Gardeners and gardening references/magazine advise keeping a gardening journal with notes on planting/harvest dates, pests and treatments and weather. And I agree! I have never done it..that smacks of being organized and that doesn’t come naturally so I skip it and test my memory! Recently, though I realized with the extra calendars my Mom gave me (she gets a dozen in the mail every year), I can use one of those as a type of journal. I can write all over it because it is just for me! I think it could be nice to know when I sowed the peas or the marigold seeds and the time it took to get to bloom or harvest. Some years I have tomato horned worm and others I don’t. Having a record could be interesting…and helpful.
DITCH THE BURLAP
I read some current gardening references that talked about wrapping those zone sensitive plants in burlap or building a snow shelter/shield around a plant. If you are not taking care of a public garden space or commercial production, then I say forget that! Plant only trees, shrubs and perennials that thrive in your zone and ditch the extra work. Admittedly I have a brown turkey fig that I place a wire cone around and fill with chopped leaves, but just for a couple years until I’m sure it is going to make it! Be aware of the snow and ice and try to track your chores to help you understand any browning or dieback that you may see. And if you miss it? Its okay! Some plants will tough it out and others you can yank out buy/start something better! Garden Regards!
Plants mentioned in this Post
Pyrocantha x ‘Mohave’– Zones 6-9. Full-sun to part Shade. Can grow 8-10 feet tall and 10-20 feet wide. Has thorns! But also fantastic fire orange berries in the fall. It doesn’t like boggy sites and after establishment can deal with drought. If you have the space this is a great shrub to train against a horizontal or fan-shape trellis. Or if you like the fancy word-create an Espalier!
Ficus carica ‘Brown Turkey’– Zones 8-11. Full Sun. Pushing it to try in my Zone 7b-some years its okay, others it get killed all the way back. In a protected spot it would do better. Can grow 15-30 feet, produces one crop a year in this zone(if all goes well). Responds well to light pruning or even espaliering.
Fun Botany Vocab!
Transpire– (of a plant or leaf)–to give off water vapor through the stomata
Stomata– the pores in the outer/surface layer of leaves and non-woody stems
Dessicate– to dry out or dry thoroughly
Cold-Hardening – the process by which some plants prepare for annual low temperatures