Winter burn on evergreens

I am always a little sad when I have to tell someone that their tree is going to die or that it is already dead. There are certain tree and shrub diseases and some species of insects that have done or will do so much damage to a tree that there is no hope for its survival, regardless of the heroic efforts put forth to save it.

When I get a picture of an evergreen tree that has turned brown, there is usually little hope of it surviving. When a deciduous tree loses its leaves, there is often still hope for its recovery. Deciduous trees have the ability to regenerate new leaves, often within the same growing season. An evergreen tree, on the other hand, does not have that same ability. Once the needles or fronds turn brown, they stay brown. Depending on the cause of the browning, an evergreen may be able to generate new growth from the tips, but sometimes the tree ends up looking like a tree made up of bottle brushes.

Many arborvitae trees succumbed to the drought of 2012. Once that species of evergreen begins to turn brown, there is not much you can do to save it.

We had numerous reports of arborvitaes dying throughout the drought areas in 2012. Unfortunately, there is no amount of tree care that can bring those trees back. The only thing that can be done with those trees is to cut them down.
It can be discouraging to the homeowner to replace the dead trees with new ones. Many times, two or three die in the middle of a row of 15 or 20 plants that have all grown to be about 8 feet tall and the biggest ones you can find as a replacement are only 4 feet high. They will eventually grow up to match the height of the other plants, but it can take many years to do so.

Sources

Evergreen Browning & Needle Drop with Alan Weninger Seasonal needle loss

In spite of being called ‘evergreens’, coniferous trees don’t keep their needles forever. Our local coniferous trees and shrubs include spruce, pine, fir larch, cedar and juniper. The loss of needles on conifers in the fall is normal and natural. This is when coniferous trees shed their oldest needles, the ones located closest to the trunk. This is called seasonal needle loss. The needles turn yellow or brown first, before dropping to the ground. If you take a peek, older evergreens don’t have much in the way of needles in the inside of the tree. Every year a conifer will grow a new set of needles and every year it will lose an old set of needles. A sign that your tree is healthy is when there is new growth in spring at the tips of the branches. No new growth on the tips of the branches indicates the branch or tree is in major trouble.

Needles in coniferous trees have a lifespan which varies depending on the species. Pines, such as white pine or scots pine retain their needles for two to three years, while spruce hold on to their needles for three to five years. In cedars, it’s normal for older branchlets to turn brown. These may stay on the plant for some time before falling off.

The exception is tamarack or larch. While these are coniferous trees, they lose all of their needles in the fall and re-grow fresh needles every spring.

Sometimes needle drop is extreme. What is the cause?

If you think that needle drop in your tree is excessive, and there is no sign of insect or disease problems, then environmental stresses are likely the cause. Extreme needle drop is often the first symptom. Stress symptoms may not appear for two to five years after the stress occurred. For example, if the area flooded around the tree three or four years ago, the damage may not fully show up until this spring.

When a tree exhibits symptoms in its branches or needles, it usually indicates a problem with the root system, specifically the tiny root hairs that are responsible for obtaining water and nutrients. Once a tree is stressed or weakened, it will be vulnerable to insect or diseases. Extreme stress, especially when it damages the root system leads to general decline in trees.

Source of stress

Effect on tree

Adverse temperatures such as extreme winter cold; fluctuating above and below freezing temperatures in mid-winter; and extreme heat in summer.

Winterkill, delayed winter injury, heat stress may cause damage to the cambian layer just beneath the bark. This damage interferes with the uptake of water and nutrients.

Drought.

Lack of water damages or kills back some of the root system, in particular the tiny and sensitive root hairs.

Flooding, including:

-overland flooding from extreme weather events,

-a high water table,

-changes to drainage (sump pump outlet or downspout directed at the root zone),

-nearby dugouts or sloughs that are full or overflowing

Prolonged exposure to standing water causes damage to the root hairs of the trees – these are specialized, very fine roots which are responsible for water, nutrient and oxygen uptake in the trees. When these roots are damaged, the trees are not able to pick up enough oxygen which is needed for photosynthesis. This causes the trees to be stressed and the needles to die out much faster than normal.

Salinity caused by high water table, sidewalk salts, road salts, nearby dugouts or sloughs.

Water in the soil that has a high concentration of soluble salts is said to be saline and causes salinity. The salts in the water is toxic to trees, shrubs and other plants.

Soil compaction from construction or heavy equipment; or when trees outgrow a space confined by sidewalks, houses or driveways.

Fifty percent of soil is generally minerals and other materials, 25% is water and 25% is air space.

Compacted soil has very low air spaces. Roots need these spaces for the uptake of water, oxygen and nutrients. Compacted soil also tends to stay wet which causes root rot.

Trees that are planted improperly. (See https://gardening.usask.ca/articles-trees/planting-practices-that-harm-trees-and-shrubs.php)

Most common effect is root girdling which leads to the death of the plant. Same with planting too deep or anything that interferes with or constricts the bark. All of these things interfere with the uptake of water, oxygen and nutrients.

Planting the wrong tree for the existing site conditions.

For example, Colorado Blue Spruce are very sensitive to prolonged exposure to standing water, a leading cause of water stress leading to extreme needle drop. They do best in soils that drain quickly.

If your site tends to be wet, try white spruce (Picea glauca). These are native to the northern boreal forest and naturally grow near streams and rivers.

Note that not all conifers respond the same way to environmental stress. For example, white spruce is native to Saskatchewan and are found throughout the northern parts of the province or near lakes, rivers and streams in the southern part of the province. Jack pines, the least ornamental of the pines, is native to the norther parts of Saskatchewan. Both white spruce and jack pines prefer a moist environment.

On the other hand, Colorado spruce and ponderosa pines are native to the side of a mountain where it is dry with sharp drainage. They are very sensitive to excessively wet soils.

So, will trees with extreme needle drop symptoms survive?

It depends on the cause of the problem and the severity of the symptoms.

For example, if water stress caused by flooding is the cause, the tree may recover provided that there are no large, repeated, long term rain events this year. It may be worth watching the tree for a while – if the buds are alive and new growth occurs, there is some hope. The tiny root hairs will regenerate fairly quickly and the tree will do better if things dry out in the summer.

Similarly, if drought has caused the problem, water your evergreen deeply every week or two at the dripline which is where most of the tiny root hairs are found.

If trees are also showing signs of insect or disease and have few needles, it may not be worth treating if the plant is in severe decline.

From driving around the county, there is no other way to put it: some trees just look bad. In actuality, the number of damaged trees is much less than the healthy ones, but those are the ones that catch our eye. There are various reasons for dying trees. Currently, emerald ash borer is wreaking havoc to many ash trees. Beech blight disease is attacking beech trees. Many spruce, especially Colorado blue spruce, have rhizosphaera needle cast or another fungal disease often causing the tree to die from the bottom up.

But this year, one disorder very prevalent, especially on evergreen trees in landscaped areas, is winter burn.

As the name suggests, winter burn (winter injury) is not caused by any living organism, so it is considered an abiotic disorder. Each year, winter burn is common, but the combination of weather conditions last fall and throughout the winter seem to have accentuated the damage this year. Winter burn is often seen on plants like arborvitae, fir, hemlock, pine, spruce, false cypress, juniper, yew and some broad leaf plants like boxwood, holly and rhododendron. Symptoms of winter burn include sections of uniform browning on the plant canopy especially on foliage on the south, southwest or west of the plant. If the damage looks more like branch tip dieback that is scattered throughout the canopy, it may have a different cause.

Winter injury is often a result of evergreen plant leaves (needles) drying out during the winter. Because the ground is frozen, the water stored in the needles needed to have been taken up by the plant before it went dormant for the winter. Therefore, anything that limited fall water uptake can make a plant more prone to winter burn. Water loss can also be due to bright winter sunlight and winter or early spring freeze/thaw cycles. Additionally, if plants are not fully dormant when the weather gets cold, winter burn is more likely.

Recommendations for saving plants with winter burn varies by plant species. For arborvitaes, boxwoods, junipers and yews, the recommendation is to prune out dead branches all the way back to alive sections of the tree/branch. If you aren’t sure if a branch is fully dead, you can scrape back a bit of the bark to check for green tissue underneath, which indicates the branch is still alive. Obviously, with some of the damage we are seeing this year, pruning out dead branches may completely disfigure the tree or leave nothing behind.

Firs, pines and spruces can often grow out of the damage, so pruning may not be needed. However, if the whole plant is brown, it likely won’t recover and should be removed.

Uncontrollable winter conditions definitely contribute to winter burn, but there are many other factors that can make it worse; some of which we can control. To minimize the chance of winter burn in the coming years, use the following guidelines:

Make wise and informed planting decisions. Before planting, make sure the plant is cold-hardy enough for where you place it or that you place it in a protected location (e.g. east side of a building, in a courtyard etc.).

Do not plant evergreens after early October. It is generally best to plant evergreens in the early spring or late summer. If trees or shrubs are planted in the mid-summer, make sure they are watered frequently to prevent water-stress.

Do not prune or fertilize evergreen trees after late summer. All pruning cuts stimulate growth at that site. If a tree puts out new growth late in the year, it may not harden off before the winter and thus is more likely to be injured. Fertilizer applications have similar results. Soil tests can help dictate whether fertilizer is needed (or not) and when to apply it.

Properly mulch evergreens. A mulch base can help with water infiltration around the tree, protecting roots from injury, and insulating roots from soil temperature fluctuations in the winter. Recommended mulch thickness varies based on soil type: clay soils should have about two inches of mulch and sandy soils should have about four inches of mulch. Preferred mulches include loose shredded hardwood, pine or cedar bark, leaf compost or wood chips. Mulch should always be at least three inches away from the trunk of the tree to minimize potential disease and rodent damage.

Water plants well. As stated above, winter burn is often a result of the plant leaves/needles drying out. Appropriate watering during the growing season can help ensure the plant is well-hydrated going into the winter.

Protect plants during the winter. A barrier of burlap, canvas, snow fencing or other materials can help minimize the likelihood of winter burn. The material should be connected to stakes placed at least two feet from the plants to provide shade and a windbreak. Wrapping material directly around trees should be avoided because it can lead to plant diseases by holding in ice and moisture.

Despite some distinctive characteristics, tree diseases and disorders can be very difficult to identify by sight. The University of Wisconsin Plant Disease Diagnostic Clinic specializes in plant disease identification. Samples can be brought into the Door County Extension Office (421 Nebraska St., Sturgeon Bay) and they typically cost $20 plus shipping.

Questions regarding backyard tree health or other insect, weed or disease issues can be sent to the Master Gardener Volunteer Plant Health Advisers who volunteer in the local UW-Extension office to help answer questions. The Plant Health Advisers are available twice a week and can be reached at 920.746.5984 or If possible, to aid us in a timely response, please submit pictures along with any question. More information about winter burn can be found at door.uwex.edu/horticulture.

How to Save a Dying Evergreen Tree

Trees like all living things have a lifecycle. During that lifecycle, they may experience periods of growth, illness, infestation, severe weather, and a myriad of other factors that may influence their livelihood, including their age.

The team at thetreecareguide.com has researched some of the leading evergreen ailments and their solutions for you to save your tree.

What Causes an Evergreen Tree to Die or Turn Brown

In order to properly treat your tree, you must first identify what is stressing it. When evergreen trees are stressed, they are not shy about showing symptoms.

The most common sign that your evergreen tree is stressed and potentially dying is the browning of a section or the entirety of the tree.

The following will help you identify and name the cause of your tree’s decline:

Evergreen Tree Diseases

NEEDLECAST – This disease is extremely common in conifers and causes very obvious symptoms. If not dealt with, needlecast can quickly propagate and spread to other trees on your property.

SYMPTOMS – The following are the three principle signs that your evergreen is infected with needlecast:

  • Browning or chlorosis (loss or abnormal reduction of the green color of needles).
  • Severe needle drop.
  • Dieback.

TREATMENT – Keep in mind that most available fungicides are most effective when applied to new foliage or before symptoms appear. The following will help you manage needlecast:

  • Prune away dead branches, twigs, and infected areas of the tree.
  • Remove fallen foliage and destroy it (burn it). Do not add to compost piles.
  • Apply a fungicide to the tree after removing signs of the infection.
  • Deep water the tree once per week to help it recover from the stress.

RUSTS – When the “raised blisters” of this family of fungi break open, the brightly colored orange to rusty brown spores are revealed (the disease is named after this coloration).

SYMPTOMS – Once the following symptoms are detected, immediate action should be taken to control and prevent the spreading of this disease:

  • Rust colored “powder” spread on the foliage.
  • Often brightly colored swellings or galls on twigs and branches.

TREATMENT – As previously mentioned, most available fungicides are most effective when applied to new foliage or before symptoms appear. The following will help you manage rust disease:

  • Prune away dead branches, twigs, and infected areas of the tree.
  • Remove fallen foliage and destroy it (burn it). Do not add to compost piles.
  • Apply a fungicide to the tree after removing signs of the infection.
  • Deep water the tree once per week to help it recover from the stress.

Environmental Factors

DROUGHT – Causes damage and death of the roots. When feeder roots and root hairs die, a water deficit occurs in the tree because these roots can no longer supply sufficient water to the top of the tree.

Drought also creates an environment for secondary infestations or disease.

SYMPTOMS – Drought symptoms may not manifest in a tree for as much as 2 years after it has occurred. But they include:

  • Heavy leaf or needle drop.
  • Drooping, wilting, yellowing.
  • Needles will show browning at the tips.
  • Cracks in the bark.
  • Dieback.
  • Thinning Canopy.

TREATMENT – There is no cure for drought, but it can be managed. By following these preventative steps, you can reduce the effects:

  • Prune back all dead or affected areas of the tree to avoid secondary infestations and disease.
  • Provide the tree with one deep watering per week, allowing water to reach down 12 to 15 inches. Several light waterings will encourage roots to grow near the surface (augmenting the problem), stick to deep watering.
  • In late fall (before the ground freezes) give the tree a final deep watering to help it avoid winter drought.
  • Mulch the area of the root spread to help the soil retain water.

Watch this video for more evergreen watering tips.

WINTER INJURY – Evergreens are particularly susceptible to winter injury. This type of injury occurs when temperatures fluctuate abnormally during the fall, winter, and spring. A warmup in the fall, a freeze in late spring, or abnormally cold winters can all have damaging effects.

SYMPTOMS – In many cases, winter injury will not be evident until mid to late spring. They include:

  • Dieback.
  • Off coloring.
  • Browning.
  • Bark splitting.
  • Heavy loss of foliage/needles.
  • Needle browning at the tip and mid section.

TREATMENT – There is no “cure” once winter injury occurs. The following will help you manage the damage:

  • Prune back all dead or affected areas of the tree to avoid secondary infestations and disease.
  • Make sure that the tree receives one deep watering per week.
  • In late fall before the ground freezes, give the tree a last deep watering to help it through the winter.
  • Provide physical protection from wind and severe winter weather. Burlap wraps function well.

Tips to Save Browning Evergreens

Saving a browning evergreen depends on how quickly the tree was diagnosed and what has caused the browning to occur. As mentioned in the treatments above, the following will help your evergreen recover if it is not already dead:

  1. Prune back all dead or affected areas of the tree to avoid secondary infestations and disease. Some cases may require extensive pruning or the removal of a portion of the tree. In this scenario, a tree professional should be called to evaluate the extent of the damage and offer direction as to which measures to take.
  2. Provide the tree with one deep watering per week in well drained soil, allowing water to reach down 12 to 15 inches. In soil with a high clay content, this interval may be every two weeks.
  3. Avoid multiple light waterings, as this will encourage roots to grow near the surface.
  4. In late fall, provide the tree with a final deep watering before the ground hardens or freezes.
  5. Mulch the area of the root spread to help the soil retain moisture. This will also help the soil retain warmth in the winter months.
  6. Verify the pH of the soil and its content. Make necessary adjustments to suit the needs of the tree species. Raise the pH using compounds with lime or limestone. Lower the pH using organic material, aluminum sulfate or sulfur will do the job as well.
  7. Fertilize only in spring and very early summer. Fertilizing in late summer or in the fall will encourage growth that will not have time to harden before winter. New growth in this manner puts unnecessary stress on the tree.
  8. Use fungicides to prevent reoccurrences of diseases. Apply only after having pruned away affected areas of the tree.
  9. Provide physical protection (especially for younger and recovering trees) during the winter season. Burlap or tree wraps work well.

If you detect that multiple evergreens are stressed and exhibiting similar symptoms, there may be a larger influence at work (including the age of your trees). If this is the case, call on a certified arborist to evaluate your entire yard or landscape.

The following video shows how fall needle drop is often confused with evergreen illness and disease. Fall needle drop is a normal process of evergreens which they will recover from.

Keeping Your Evergreen Trees Healthy

The best measure of treatment for all trees and plant life is to keep them healthy, planted in the right location, and properly watered.

For the trees you are able to recover, keep a close eye on them for secondary infections and infestations. Trees take time to heal and strengthen their defenses.

Once your trees have had problems with disease or drought, schedule an annual inspection by a certified arborist to ensure that any residual or new problems are properly addressed.

Sources:

Evergreen Shrubs: Is it Normal Discoloration, or Winter Damage?

Are you worried that this winter’s weather caused more damage than normal to your landscape? Here is how you can tell if your discolored evergreen plants are simply affected by cold, or actually dead.

Many species of evergreen trees and shrub will turn bronze or brownish in the winter. This color change is a reaction to low temperatures and sunlight-usually the more sunlight the plant receives the more pronounced the change is, and can range from olive-green to nearly purple. It’s usually referred to as “winter bronzing”.

The bronzing is caused by mild desiccation of the needles or leaves, dulling the green colors normally seen in warmer weather and allowing the underlying brown, rust or purplish colors to show through. This is similar to why deciduous leaves change color in the fall—after the green chlorophyll dies in preparation for winter, the true color of the leaf is revealed. (Neat, huh?) As winter progresses, the ground freezes and the sun and wind evaporate more water from the leaves or needles than the plant can uptake to replace it, and the plant gradually turns from green to brown, bronze, or even orange or purple.

“Really dead” evergreens are brown in a different way. Instead of a gradation of colors from olive-green to bronzy-purple, dead branches are uniformly orange-brown to dark brown. Where a branch with winter bronzing is still flexible and supple, a dead branch is “crispy” and often snaps when bent.

When a single branch or “chunk” discolors like this while the rest of the plant stays green, that section is usually dead. Test by scraping the bark with your fingernail. If you see green below the brown or grey bark the branch is alive. If it’s brown it’s dead, and a sickly olive green color indicates it is dying. You can safely prune out dead sections without hurting the plant; if the damage was limited, you may barely even notice the loss. If only the ends of the branches are dead, prune back to the point where the fingernail scrape test indicates it’s still alive. You may need to do a little additional pruning to even everything out.

If larger areas die out, sometimes the symmetry of the shrub is ruined. For some shrubs (azaleas, abelias, hollies and others), a hard renovation pruning will allow the entire shrub to regrow evenly. In other shrubs, including many (but not all) needled evergreens, the loss of a section is never fully recovered because of the way they grow. In those cases, replacement is usually the best option.

What Is Winter Burn: How To Care For Winter Burn In Evergreens

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. This problem is called winter burn. 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.

How To Help Evergreen Shrubs With Winter Burn

For people living in cold climates, a sunny, warm day that interrupts an otherwise gloomy winter is something to look forward to.
For evergreens in cold climates? Well…sunny winter days aren’t so sweet. Harsh sun actually works against evergreens in winter. Come springtime, these endlessly green plants might turn brown from the damage.

Below, find out why your evergreen shrubs may not have gotten off to a good start in spring.

My Evergreen Shrubs (Boxwood, Dwarf Alberta Spruce) Have Winter Burn. What Now?

Winter burn sounds pretty straightforward, but what exactly does it mean?

Here’s the gist—evergreen shrubs, unlike other plants, hold on to their foliage in winter, and it takes tons of moisture to keep their needles green throughout the season. Anytime bright sun or harsh wind is in the forecast, the needles lose moisture, and since the ground is frozen, plant roots just can’t take up enough water from the soil to replace that lost moisture. Eventually, the needles get way too dry, causing winter burn.

How do I know if my shrubs are affected?

Winter burn starts with the tips of shrub needles turning brown, and then eventually full needles on a whole section of the tree are brown and dry.

Not surprisingly, the discolored section appears on the side of the plant that gets the most sun or wind throughout winter. But that doesn’t mean winter burn is immediately obvious. Evergreen shrubs might look green and healthy leading up to spring, and then start to turn brown just as the growing season arrives.

What are some tips for winter burn treatment? Will my shrubs recover?

Odds are, an evergreen shrub that has winter burn will bounce back. Even though brown chunks might make the plant look dead, your shrub will more than likely sprout new needles.

To be sure, prick a small area of an affected branch with your fingernail or a pocket knife. It should be green and moist underneath. Any branches that are still green under the bark are alive and can grow new needles. If any branches are brown and dry underneath, you should prune those out.

Lastly, make sure your shrubs get lots of water throughout spring. They’ll thank you with a flush of new green needles!

Can I prevent winter burn before next year?

Kudos to you for thinking ahead! Yes, there are steps you can take to protect your shrubs.

Here are four things you should do to prevent evergreen winter burn:

  1. Thoroughly water your shrubs in fall all the way up until the ground freezes. Hydrated plants have a much better chance at dodging winter burn.
  2. Apply 3-4 inches of mulch to the ground beneath your shrubs and trees. That’ll seal in the moisture you’re giving them when you water.
  3. Try an anti-desiccant spray. It’s a wax-like coating that helps evergreens avoid moisture loss in winter. Read more about anti-desiccant sprays in this blog post.
  4. If your shrubs are directly exposed to harsh sun or wind in winter, wrap them for protection. Here’s how to wrap an evergreen shrub with burlap.

Winter Burn On Evergreens

Most of our evergreen species are narrow-leaved conifers – Pine, Spruce, Arborvitae, Juniper, Hemlock, and Yew – that have needles or scales for foliage. Unfortunately all of these species can be injured by winter burn. Winter burn injury is observed on many evergreen trees and shrubs every winter.

Symptoms of winter burn are browning or bleaching of foliage, particularly on the south, southwest, and windward sides of plants. Evergreen foliage buried under snow is usually protected from damage while plant parts above the snowline are often damaged. In severe cases, the entire plant may turn brown and die. Sometimes symptoms occur immediately as damage occurs, but often symptoms appear or worsen as temperatures rise in late winter and early spring.

Winter burn results from water loss in plants during winter. During the growing season, water is absorbed and pumped from soil into the roots of plants. From there, streams of water are suctioned up into a plant. Some of this water is used for plant growth and reproduction. The vast majority of this water is lost during transpiration, as water is released back into the atmosphere through small openings called Stomates on the lower surface of leaves. This lost water is quickly replaced as roots continue to absorb and pump water from soil into plants.

As plants acclimate and prepare for winter, deciduous trees and shrubs drop their leaves with their thousands or millions of Stomates. Because evergreen woody plants retain their foliage, transpiration, and loss of water from Stomates continue during winter. This is especially true on sunny, and windy, winter days when higher temperatures and wind speeds increase transpiration rates. Because roots in frozen soil have no ability to replace this water, winter burn occurs as leaves desiccate, die, and turn brown. In more severe cases, buds, stem tissue, or entire plants may die.

If leaves are dead, but buds and stem tissue are still alive, new plant foliage will regrow to replace winter burned foliage. On the other hand, if buds and stem tips were damaged, branches should be pruned back to ¼” above a bud in the live portion of the plant. As with any tree under stress fertilizing will help it remain healthy. In severe cases the entire plant may have died and plant removal and replacement will be necessary.

To help prevent winter burn in the future, keep evergreens properly watered throughout the entire growing season until ground freezes.Try to maintain a 3-4″ layer of organic mulch around evergreens to help retain soil moisture throughout the growing season. As this mulch breaks down, it will also improve your soil’s moisture holding capacity.You can protect plants in highly exposed sites during winter with burlap. snow fencing, or other materials to prevent too much exposure to sun or wind.

SummaryArticle Name Winter Burn On Evergreens Description Most of our evergreen species are narrow-leaved conifers – Pine, Spruce, Arborvitae, Juniper, Hemlock, and Yew – that have needles or scales for foliage. Unfortunately all of these species can be injured by winter burn. Winter burn injury is observed on many evergreen trees and shrubs every winter. L.C.S. Lawn LCS Lawn L.C.S. Lawn and Tree Service L.C.S. Lawn and Tree Service Publisher Logo

Winter damage on conifers beginning to show up

Winter injury can affect most Christmas tree species and other conifers. The winter of 2017-18 did not seem to be colder than normal, so it is surprising to see conifers beginning to show the classic symptoms of winter injury. The warm and dry fall may have stressed trees before going into winter and could be contributing to the winter injury we are seeing. Growers are reporting they are seeing damage on many species including Dwarf Alberta spruce, white pine, Douglas-fir, Fraser, Canaan and Concolor firs. The most obvious symptom of winter injury is browning needles, especially on the south side of the tree or above the snow line.

The first type of damage we find is often called winter drying. Drying occurs when the soil is frozen and the roots cannot easily replace water when the trees loose moisture in the winter due to wind or sunny conditions. The second type is referred to as winter burn. This happens when needles or buds are damaged after rapid temperature changes. This most often occurs on the south side of the tree where the sun reflects on the snow and warms the tree during the day and then at night the temperatures drop. In a year like this, growers may be experiencing both winter drying and burn.


Winter damage to Douglas-fir. Note the browning above the snowline.

To complicate matters, there is also browning on Austrian pine due to Dothistroma needlecast or Swiss needlecast on Douglas fir. In addition, some trees may have died over the winter from compromised root systems caused by J-rooting or Phytophthora root rot in Fraser fir. Once you can get into the field, look closely at the trees to determine what the true cause is of the symptoms you are observing.

Damage can vary from year-to-year and site-to-site. The long-term impact depends on whether or not buds are killed. We can often see needle browning without bud-kill. If buds are also killed, which we are seeing this winter in some cases, it will take longer for trees to recover. To help trees recover, try to minimize stress this growing season through weed control, irrigation, etc.


Left/top, A healthy bud. Right/bottom, A bud damaged from cold winter temperatures.

Browning of Conifer Needles

The Plant Disease Clinic has recently received several samples of white pines and other conifers that are turning brown. Many factors may cause browning of conifer needles.

The most common cause of brown needles is winter browning. Evergreen trees continue to produce energy from sunlight (photosynthesize) throughout the winter, which requires water. If these trees do not have sufficient stores of water from the fall to last through the winter, they may dry out and their needles turn brown. Frequent freeze/thaw cycles, cold temperatures, and rapid temperature changes increase the rate of drying. This browning may appear more pronounced on the sunny (south and west) sides of the tree. Winter browning typically becomes visible in late winter or early spring.

It is often recommended that trees be watered intensely once in the fall, right before the ground freezes, to prevent winter browning. Studies have shown that this one watering late in the fall is insufficient to protect trees from winter browning. Trees need the extra water during the dry period of late summer and early fall to prevent drought stress and ensure that they have sufficient water stores to last the winter. Preventing drought stress in late summer is more effective at minimizing winter browning than one watering in the late fall. Brown branches on affected trees should not be pruned off, as they may still have viable buds.

Evergreens near roads may also turn brown in the winter due to exposure to road salts. Some infectious diseases also cause browning of needles. These symptoms usually appear in the spring or summer, although some people do not notice them until winter. Common needle diseases of evergreens include Rhizosphaera needle cast of spruce, Dothistroma needle blight of Austrian pine, and Diplodia tip blight of Austrian and Scots pine.

White pine sample showing browning of needles from winter drying.

Concolor fir tree with brown needles from winter drying.

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Voles can do this kind of damage to junipers.

(George Weigel)

Q: This past winter, I wrapped my junipers with burlap so there wouldn’t be any damage from snow and ice like the previous winter. Now the branches are turning brown and falling off.

Some parts of the plants are pushing out new growth, but the centers look dead. I took the burlap off the first week of April when temperatures got into the upper 60s. What did I do wrong?

A: I don’t think that’s cold damage. Most junipers are plenty winter-hardy.

However, they are prime targets for vole damage over winter. Voles often chew the roots and the base of juniper trunks over winter when they can’t find much better to eat. That can result in browning of the branches supported by the damaged roots.

I once lost a whole specimen juniper to voles. I couldn’t figure out what went wrong until I dug it up and found that all of the bark had been chewed off the roots and around the base of the trunk.

Last year voles even killed a 25-year-old apple tree in my yard when they ate a band of bark from around the base of the trunk. They’re very destructive and not obvious since they do their damage underground or low on the plants.

They also tend to pick on evergreens like junipers because of the protection those plants give from hawks. If anything, burlap gives them even more protection from predators.

Burlap “breathes” well enough that it typically doesn’t cause overheating or sun scald that a wrap such as clear plastic can do. Even still, it’s best to wrap burlap around stakes to make a windbreak around the plant’s perimeter as opposed to draping it or securing it right against the needles.

Voles are plant-eating small rodents that try to stay hidden and out of the open.

It’s almost impossible to protect plants from voles, so the best strategy there is to trap the voles with either snap traps or cage traps and peanut butter as bait. Here’s a link to a post I did a few years ago on dealing with voles.

Another possibility for your browning is one of two blight diseases that attack junipers. These usually start with random brown tips, spreading to kill whole branches and possibly whole plants.

When you look at the needles under a hand lens or other magnification, you can see little black dots (like pepper) that indicate fungal spores. That’s a telltale sign of blight.

These diseases are hard to stop, other than with regular spraying of fungicides. I usually lean toward pruning off dead tips and dead wood and relying on the plant’s immune system and uninfected wood to grow through the infection.

In the long run, it’s cheaper and easier to just replace blight-infected plants than to keep buying sprays and applying them about four times every year. Unfortunately, you can’t just spray once and kill off the disease.

Large sections of the outer branches on my holly bush have brown, dried leaves this spring. It was fine in the fall, but now I’m finding all these brown leaves. What’s going on?

Occassionally in spring homeowners may find dead, reddish-brown foliage on their needle evergreen plants, such as pine, spruce, fir, juniper, arborvitae and yew, on on their broadleaf evergreens, such as holly and mahonia. The extent of the symptoms can vary from brown needle tips on one side of the plant, to one or two branches, to the whole tree. Injury is found on the outer portion of the branches and is often most severe on the side of the tree facing the wind or a source of radiated heat, such as a south or west-facing brick wall or street.

Winter desiccation is a common type of winter injury that occurs when the amount of water lost by the foliage exceeds the amount picked up by the roots.All trees lose water during normal metabolic processes, even in winter. During the growing season when trees are in full foliage, large amounts of water are lost through their leaves. During winter months, photosynthetic processes are slowed, but evergreens continue to lose water at a higher rate than deciduous trees, through their needles and to a lesser extent from exposed bark, twigs and buds.

Warm, sunny days or windy conditions increase the amount of water lost from the needles. If the soil is frozen or soil moisture is low due to dry conditions, plant roots are unable to pick up enough water to meet its needs. Needles dry out and die, but they may hold their green color until warmer temperatures arrive in spring, thus delaying the onset of browning symptoms.

Winter wind accompanying dry periods can accelerate water loss from the needles, and needle death is more extensive on the side of the tree facing the prevailing wind. Other common terms for this type of injury are winter burn, winter drying or winter scorch.

Symptoms

When water usage exceeds available water, the needles, leaves and twigs dry out and die. Usually evergreen leaves or needles hold their green color even after the injury has occurred until warm spring temperatures arrive, resulting in delayed browning symptoms. Affected needles turn yellow or reddish-brown at the tip, and dieback to the base.

Often the pattern of damage is directional, on one side of the tree more than the other. Wind accompanying dry periods can accelerate water loss from the plant and result in damage that is more extensive on the side of the tree facing the prevailing wind, particularly those with southern or western exposures.

Another factor that can contribute to a directional pattern of browning is solar radiation reflected from hard surfaces such as brick siding, pavement, light-colored metal siding or white lava rock mulch. Evergreen trees planted along streets may show browning of the foliage nearest the roadway. Foundation plantings of yew, juniper, dwarf Alberta spruce and arborvitae located around buildings show browning on the side next to the house.

Factors that can predispose evergreen trees to winter desiccation are 1) white or lava rock around the base of the tree; 2) poorly develop root systems due to improper planting; 3) girdling roots; 4) root injury; 5) soil compaction; 6) stress due to insects or disease; and 7) tree genetics, i.e., trees from a southern United States source.

Management

No immediate action should be taken with evergreen plants showing winter injury other than supplemental watering if conditions are dry. Evergreen trees with a small amount of needle loss may still have live buds within the damaged branch sections. These buds will send out new growth and eventually fill in the damaged section in a few years. Evergreen shrubs, like holly and mahonia, may regenerate new leaves to replace the damaged foliage if injury was not severe enough to kill the underlying branches.

Pruning- Wait until new growth has emerged before pruning out dead branches. After the new growth has emerged, prune out any dead branches or branch tips, cutting back to 1/4″ above a live bud. It is important to remove dead branches. They can provide an entryway for insects or fungi that attack the dead tissue.

Summer watering- The key to preventing winter desiccation is to maintain adequate soil moisture throughout the summer and into winter. Provide damaged plants with one inch of water per week, allowing them to growth vigorously and avoid further injury next winter. Trees that have suffered from drought conditions at any time during the year will not be able to withstand dry winter conditions as well as trees that have consistently received adequate moisture.

Winter watering- Many people put their water hoses away for the winter, but periodic watering during the fall and winter at times when the ground is not frozen can be very beneficial. Trees and shrubs benefit from slow, deep watering with a hose that has been left to trickle for an hour or so. Turfgrasses also benefit from a periodic deep watering.

Mulching- Apply a 3-6 foot diameter ring of mulch around the base of trees and shrubs, with 3-4 inches of an organic material like coarse wood chips. This helps conserve soil moisture and prevent deep freezing of the soil in winter.Relocation- Susceptible trees and shrubs may be protected from prevailing winter winds next year by erecting a lath or burlap screen on the south or southwest side in fall, or by transplanting them to a more protected location.

Loss of trees due to winter injury is unnecessary and costly, not only in monetary terms, but in intangible values such as shade, protection and beauty. Since Nebraska frequently experiences dry fall and early winter conditions, deep-watering trees in fall may mean the difference between healthy, vigorous trees or stressed, struggling trees next spring.

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