What Is Winter Burn: How To Care For Winter Burn In Evergreens
By: Bonnie L. Grant, Certified Urban Agriculturist
Spring gardeners may notice that some of their needled and evergreen plants have brown to rust areas. The foliage and needles are dead and appear to have been singed in a fire. What is winter burn and what causes it? The damage is from dehydrated plant tissues and occurs during winter when temperatures are frigid. Winter burn in evergreens is a result of a natural process called transpiration. Preventing winter burn will take a little planning on your part but it is worth it to protect the health and appearance of your plants.
What is Winter Burn?
When plants gather solar energy during photosynthesis, they release water as part of the process. This is called transpiration and results in the evaporation of moisture through the leaves and needles. When a plant is not able to replace the lost water due to drought or heavily frozen ground, they will dehydrate. Winter burn in evergreens can cause death to the plant in severe cases, but most likely results in foliar loss.
Evergreen Winter Damage
Winter burn shows up on evergreens as brown to red dry foliage or needles. Some or all of the foliage may be affected, with areas on the sunny side most severely damaged. This is because the sun’s rays intensify the photosynthetic activity and cause more water loss.
In some cases, the new terminal growth will die and buds may fall off plants, such as with camellias. Stressed plants, or those that were planted too late in the season, are especially susceptible. Evergreen winter damage is also most severe where plants are exposed to drying winds.
Preventing Winter Burn
The best method for preventing winter burn is to choose plants that are not as prone to this winter damage. Some examples are Sitka spruce and Colorado blue spruce.
Situate new plants out of windy zones and water them well as they establish. Water during winter when soil is not frozen to increase moisture uptake.
Some plants may benefit from a burlap wrap to insulate them from drying winds and help prevent excess transpiration. There are anti-transpirant sprays available but they have limited success in preventing winter burn.
Winter Burn Treatment
There is very little you can do to treat burned plants. The majority of plants will not be severely injured, but they may need a little help getting healthy again.
Fertilize them with the proper application of food and water it in well.
Wait until new growth has begun and then remove those stems that were killed.
Provide a light application of mulch around the root base of the plant to help conserve moisture and impede competitive weeds.
The best idea is to wait for a while and see if the damage is permanent before embarking on any winter burn treatment methods. If winter burn in evergreens is persistent in your area, consider erecting a windbreak of some kind.
Remove trees that succumb to evergreen winter damage before they become magnets for insects and disease.
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What Do I Do to Fix Evergreen Shrubs That Have Browning Branches?
Evergreen shrubs can be focal points in a home garden, bringing green accents to the landscape year-round and providing cover for birds and wildlife during the colder months. Sometimes evergreen foliage and branches might turn brown, an unattractive change that can signal an environmental or cultural problem. Identifying the cause and deciding on the best course of action can help the plant survive and recover.
Published by [email protected] Guide to Landscape Design & Maintenance
Welcome! I am a landscape/garden designer, consultant, garden blog and book author involved in the design profession since 1996. I have a true passion for horticulture and design and believe that good communication between designer and client is the key to achieving the ideal landscape. I am involved in blog writing so that I can share my love of gardening with others. With shovel in hand since the age of five, gardening has been and always will be a part of me. View all posts by [email protected] Guide to Landscape Design & Maintenance
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I am a landscape/garden designer, consultant, blog author and published book author, involved in the horticultural industry since 1996. A Guide to Landscape Design & Maintenance-Long Island is my newest blog addition which focuses on a variety of topics dealing with landscape design and general garden maintenance. While monthly timing of topics is aimed towards conditions for zone 7, the information presented here can certainly be used by most other hardiness zones. Thank you for visiting!
Protecting Broad-leaved Evergreens for Winter: Anti-Desiccant Spray
The temperatures are dropping rapidly here in the northeast and it is time to apply anti-desiccant spray to your broad-leaved evergreens to protect them from winter damage.
What is desiccation?: Certain broad-leaved evergreens are susceptible to winter burn and drying from harsh winter winds here on Long Island and anywhere where winter temperatures drop below freezing. Desiccation, or extreme drying is caused by moisture loss from the leaves by transpiration. A precautionary measure for this drying is the use of an anti-desiccant, which can help to prevent damage to your landscape plants. Anti-desiccant spray is an organic based spray application that lasts for approximately three months throughout the winter, and helps to prevent water loss from your evergreens.
Which plants should be sprayed with an anti-desiccant?: Apply an anti-desiccant spray to your broad-leaved evergreens such as holly, rhododendron, cherry laurel, skip laurel, mountain laurel, Japanese skimmia, leucothoe, aucuba and boxwood when the daytime temperatures start falling below 50 degrees (around Thanksgiving here in zone 7 Long Island). Apply when the temperatures are above freezing and there is no threat of rain or frost within 24 hours. (This tip applies to areas going into their winter season-temperatures dropping below freezing: 0 degrees Celsius or 32 degrees Fahrenheit.)
When to Apply: Apply anti-desiccant when the daytime temperatures start falling below 50 degrees (late fall/early winter). Apply when the temperatures are above freezing and there is no threat of rain or frost within 24 hours.
Dangers: Be sure to read all directions on the label since anti-desiccants can cause photo toxicity on some narrow needled evergreens such as Arborvitae and Spruce that could cause more harm than winter burn. Spraying in freezing temperatures will do harm to the plant. Do not spray in freezing temperatures and allow time to dry before temperatures drop below 32 o F or 0 o C.
How often should I apply anti-desiccant?: Sudden warm spells can trigger your evergreens to open their pores allowing for more water loss. If there is a winter thaw part way through the season it is recommended to re-spray your plants but only if the temperatures are to remain above freezing for at least 24 hours.
Where do I purchase anti-desiccant?: The most commonly used brands of anti-desiccant are Wilt-Pruf, Vapor Guard and Transfilm that can be found in nurseries and garden centers. There is a new brand of anti-desiccant on the market which requires only one application. Ask your landscape professional for more information.
Author: [email protected] Design By Lee 2016. All Rights Reserved.
How to Prevent Leaves From Browning Due to Winter Burn
So how do you prevent arborvitae leaves from turning brown? And if browning does occur during the cold-weather months, what action, if any, should you take once spring returns? Let's begin with five prevention tips:
- Select a sheltered location at planting time
- Water in late fall
- Water during thaws
- Mulch over the root zone
- Protect with tree wrap
Regardless of the type of arborvitae you plant, your best bet for avoiding winter burn is to wrap the arborvitae in burlap. Placement in the landscape can also help prevent browning: Avoid planting arborvitae on the south side of a wall (the sun can be an enemy in winter) or in an area exposed to high winds. Ease up some on watering arborvitae in September to encourage hardening off, then maintain adequate irrigation from October until whenever the ground freezes in your area. Such an irrigation regimen will help prepare the shrubs for winter.
Also look for opportunities to water your arborvitae shrub during the winter. You have probably heard the term, "January thaw," right? If the ground thaws out at some point in the winter (thaws can happen in February, too), take advantage. With the soil loose again thanks to the thaw, any water you spray on the ground can permeate down to the plant's root zone once again. This drink could help your shrub in the same way that a glass of water slakes the thirst of a wanderer in the desert.
Another preventive measure is to apply garden mulch around your arborvitae. Winter burn is a moisture issue, and mulch helps conserve moisture in the soil around a plant.
Arborvitae branches whose foliage turns brown (entirely) due to winter burn may not come back, but there is no sense in being hasty about pruning (you never know), so hold off on pruning until well into the spring or even summer. Only time will tell as to whether your arborvitae branches will recover from winter burn there is not much you can do to reverse the damage that results in brown foliage. Instead, direct your efforts at preventing winter damage in the future. If green growth does, eventually, re-emerge on a branch damaged by winter burn, prune the branch back as far as that greenery. But if the arborvitae branch never shakes the "brown look," just prune if off entirely. Depending on how severe winters are in your region, you may also have to prune arborvitae because of snow damage.
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"Well winter is over and did we have a long one this year!"-- is our mantra in New England come Spring.
The good news:
- A winter with heavy snow gives plants great insulation at their root, and frost never really develops in the soil.
- Insulating the roots typically gives plants a stronger root system & they could produce more flowers/fruits the upcoming year
The bad news:
- Many tops of larger broadleaf everygreens were expsoed to the cold winds & could not get ample water to remplish themselves
- In areas where snow did not mels, the stems froze, causing some death to the leaves and stems
So what happened to your plants?
Everywhere I drive I see many broadleaf evergreens that show signs of winter damage. I don't believe that all of these plants are dead. Many of the leaves will fall off and new growth should replace the plants in late spring.
Time will heal all and you must be patient and wait until the temperatures warm up to see what is alive vs. dead. You could remove any of the dead leaves, this will advance the new growth behind the leaf. If the stems are brown and the leaves then those parts are considered dead.
In winters with little snow, there is no insulation to prevent roots from freezing and thawing, which leads to death for many plants. A few years ago, for example we had no snow cover and plenty of cold temperatures, complicated by cold winds. Many plants desiccated and died, even varieties that are considered hardy in this region.
What is Latent Winter Kill?
Later this spring, you may see some latent winter kill, especially with the build up of snow and ice around the main trunk and branches of some plants. What happens is the cold ice freezes the cambium (tissue of the plant). The plant has stored energy in the stem.
Once the warm temperatures of spring start, the plant relies on the stored energy in the roots and stems to develop the leaves or flowers. If the winter froze and killed off any of the stored energy in the stem, then the plant will start developing growth from the roots.
Sometime in May the plant is looking to use the stored energy in the stem and it is gone. Then the plant will show stems and foliage dying.
Most customers that see plants developing growth and then see it browning or dying assume an insect or disease has consumed it and we should have a product to remedy it. This is not the case. You can’t fertilize or spray any product to revive the dead.
It is possible that only a few branches on certain sections of the plant will show damage, if that is the case prune off those dead branches. You can also fertilize the plants with Holly-tone and water when necessary. Proper pruning is crucial to plant health.
As you look at the plant material in your yard, pay close attention to splitting branches on shrubs and trees and road salt damage. These are the other major problems that affect the way plants will grow.
Watch out for Damage from Build Up of Snow and Ice
Build up of snow and ice on the branches of many plants will cause breakage. Some plants are more resilient to the weight and will bounce back. Many other plants are fragile and because of the heavy snow in March, you will see plants with cracked stems or branches.
If any plants have branches that are broken, regardless of their size, you can’t tape them back together. Once the wood is exposed, rot will shortly develop in that location.
The only way to prevent the plant from dying is to prune the branches off below the damage, to the next set of healthy branches. In most cases, new growth will develop from that junction to replace the broken branches.
Use proper pruning techniques with the correct tool. If many branches have been broken and the plant has lost 50% or more of growth, we would recommend replacing the plant.
Identifying Sun Scald & Winter Burn
March also gave us a lot of sunny days. We all hoped it would melt the snow instead the sun intensity compiled with the snow reflection and cold temperatures create burn and frost cracks on many plants.
You will notice evergreens with just one side having browning foliage. This is only burn to the foliage and we would not recommend pruning any branches until you check to see the viability of the stem. If the stems are alive then many of the evergreens will have new growth coming in late May to replace the brown foliage.
Please wait until late May before pruning. While winter damage can make plants unattractive, you may be removing healthy stems that could look like a new plant by late spring. If you do notice that the stems are completely dead then it would be recommended that you prune.
In most cases the burn will be on the west facing locations. That is because of the suns’ intensity. Usually thin barked trees, like Kwanzan Cherry, Red Maple and Dogwoods get frost cracks on the main trunk, probably on the west side.
Frost cracks will not kill the tree. Usually a new bark forms over the crack and in time the tree will heal itself. Later in the season people may find insects residing in or near the crack.
They are there because it is a great place to hide and live. They are not the reason for the crack. If the tree is not doing so well you probably have another problem on your hands.
How do you fix the problem?
The best way to prevent winter damage is by watering your plants well into the fall until the ground freezes, this is typically around Thanksgiving. You could also spray an antidesicant in the Fall, and be sure to mulch your plants heavily before winter snows begin.