White paint tree trunks

Painting Tree Trunks White: How To Paint Tree Bark

Trees are amazingly adaptable and vigorous, providing protection for us and a host of other species. Young trees need time to get strong and impervious and need a little help from us to survive the first few years. Tree trunk painting is an old-time method to seal trunks and protect them. Why do people paint trees white? Painting tree trunks white has several purposes and can help shield saplings and very young trees from a variety of damage. Find out how to paint tree bark to help minimize insect damage, sunscald and cracked, damaged bark.

Why Do People Paint Trees White?

Painting tree trunks white is a time honored method of young tree protection often found in orchards and tree farms. There are several purposes but chief among them is to prevent cracking and splitting of the tender new bark, which can allow introduction of disease, insects and fungus. It is also helpful to highlight insect infestations and may prevent some borers.

There is some debate as to the effectiveness of tree trunk painting. It certainly directs burning sun rays from the tender bark, but the wrong product can cause more harm than good.

White Tree Trunk Paint

The proper product to use for tree trunk painting is water-based latex paint. The paint needs to be diluted at a rate of one gallon latex mixed with four to five quarts of water. A Cornell University study found that a full strength application painted on protected best against borers. Another formulation is one-third each water, latex paint and joint compound, useful for sunscald protection.

Never use an oil-based paint, which will not allow the tree to respirate. If rodents such as rabbits are nibbling on your young trees, add a rodent repellent to the white tree trunk paint to prevent their gnawing damage.

While some experts say to only use interior paint, others recommend the opposite. Really, as long as it’s latex paint, either should work fine. Keep in mind, however, that some paint may contain additives that can be harmful to plants, so check this beforehand. In fact, looking for one with an organic base may alleviate this concern. Also, in addition to white, you can actually use any light color paint and get the same results — just stay away from the darker tones which will absorb heat and cause further sunscald.

How to Paint Tree Bark

Once you have mixed your paint mixture, the best method of application is by paintbrush. Tests indicate that spraying doesn’t provide adequate protection and does not stick as well to the bark. One single coat is sufficient in all but the most severe conditions.

Painting tree trunks white is an easy and fairly non-toxic way to protect your plant from several different problems. The process is easy, cheap and only needs to be done once per year in extreme weather zones.

Mar 30, 2012Painting tree trunks protects against rodents, borers

Painting fruit tree trunks with white latex paint can prevent the bark from splitting and cracking off. Splitting can happen when the tree is exposed to freezing evening temperatures, followed by a daytime thawing. The painted white trunk will help reflect sunlight during the daytime hours and keep the tree warmer at night, according to a University of Missouri Extension website.

Painting is also one of the ways growers can protect their trees from rodent damage. In northern climates, mice and voles can girdle a tree under the snow cover. Rabbit damage can also be prevented by adding a rabbit repellant to the paint mixture, according to a report from the University of Vermont.

On the Virtual Orchard Internet listserv, several growers recently discussed other effects they have noticed from painting tree trunks.

“I have noticed a very surprising and useful side effect of painting the lower tree trunks in my orchards with undiluted white latex paint,” said Randy Steffens of Shepherd’s Valley Orchards, Chattanooga, Tenn. “I have found this practice completely eliminates damage caused by rabbits chewing on the trunks, and I haven’t had to add anything. I’m not sure why this works (perhaps the rabbits in Tennessee are not as voracious as elsewhere), but for me, it is absolutely stunning how effective it is.”

At Shepherd’s Valley, the use of paint has made rabbit guards obsolete, Steffens said. He even painted after the rabbits started eating the bark in the fall. A white, latex-paint application completely eliminates the problem for him, he said.

“Usually, the rabbits take a bite or two of a few painted trees and then leave them alone for the rest of the season,” he said. “These results have been predictably occurring for a few years now, ever since I started the practice of painting my trunks.”

It isn’t just mice, voles and rabbits that the practice helps. Boring insects have taken a dislike to the practice too, said Kevin Hauser of Kuffel Creek Apple Nursery, Riverside, Calif.

“If it works again this year, I’m ready to declare victory, as we’ve gotten hammered from borers over the last several years,” Hauser said. “We’ve settled on one-third white paint (I use Glidden Gripper paint), one-third all-purpose drywell joint compound and one-third water. This brushes on well, but makes a thick coat.”

Hauser credited John Bunker of Fedco Trees in Maine for originally using drywall joint compound.

“They use it to prevent winter sunscald, and I used it initially to prevent summer sunburn,” Hauser said.

A study by David Kain and Art Agnello at Cornell University backs up the claim about borer activity.

“In a previous study, we had applied a 50:50 mixture of water and white latex paint using a sprayer,” Kain said. “While spraying paint on was efficient, it was not effective at the 50:50 rate in preventing dogwood borer infestation. In this study, we applied the paint at full strength with a paintbrush. While this took considerably more time than spraying, it was effective and long lasting.”

According to the study, in a few instances burrknot tissue grew through the paint layer and became unprotected, opening the door for tissue damage and infestation issues, Kain said.

By Derrek Sigler, Assistant Editor

Tags: Apples, Fruits, Water

Natural-looking paint for citrus trunks

If you live in southern Arizona’s citrus-growing belt, you’ve probably seen oranges and other trees with stark white trunks. There’s a good reason for painting the exposed bark of citrus. It is particularly sensitive to sunlight, and the paint reflects the ultraviolet rays that can cause sunburn and cracking. Unfortunately, white trunks stick out like sore thumbs in the landscape.

Now there’s an alternative. Go Natural paint was developed by Chuck Robbins, a former citrus-grower in Mesa, Arizona. Formulated to match the natural color of citrus bark, the paint provides the same ultraviolet protection as white latex but lasts longer. You can use it to coat other thin-barked fruit trees such as peaches, and it will also protect the bark of young landscape trees. Like any latex paint, you can apply it with a brush, roller, or sprayer, and it cleans up in water.

Go Natural paint is sold in 1-quart, 1-gallon, and 5-gallon containers at many nurseries and garden centers in Arizona. Call (480) 396-0116 for local retailers.

Anatomy of a tree

This information is courtesy the Arbor Day Foundation

A: The outer bark is the tree’s protection from the outside world. Continually renewed from within, it helps keep out moisture in the rain, and prevents the tree from losing moisture when the air is dry. It insulates against cold and heat and wards off insect enemies.

B: The inner bark, or “phloem”, is pipeline through which food is passed to the rest of the tree. It lives for only a short time, then dies and turns to cork to become part of the protective outer bark.

C: The cambium cell layer is the growing part of the trunk. It annually produces new bark and new wood in response to hormones that pass down through the phloem with food from the leaves. These hormones, called “auxins”, stimulate growth in cells. Auxins are produced by leaf buds at the ends of branches as soon as they start growing in spring.

D: Sapwood is the tree’s pipeline for water moving up to the leaves. Sapwood is new wood. As newer rings of sapwood are laid down, inner cells lose their vitality and turn to heartwood.

E: Heartwood is the central, supporting pillar of the tree. Although dead, it will not decay or lose strength while the outer layers are intact. A composite of hollow, needlelike cellulose fibers bound together by a chemical glue called lignin, it is in many ways as strong as steel. A piece 12” long and 1” by 2” in cross section set vertically can support a weight of twenty tons!

Leaves make food for the tree, and this tells us much about their shapes. For example, the narrow needles of a Douglas fir can expose as much as three acres of chlorophyll surface to the sun. The lobes, leaflets and jagged edges of many broad leaves have their uses, too. They help evaporate the water used in food-building, reduce wind resistance— even provide “drip tips” to shed rain that, left standing, could decay the leaf.

Why do leaves turn color?

If you think you know the answer to that question, you don’t. Or, you might.
Almost every tourist, when first encountering palm trunks outfitted in pancake makeup, has asked the question. I know I did.
The best thing is that there are plenty of answers. The problem is that no one really knows what the correct answer is. In this world of terminal relativism, maybe they are all correct. Or maybe none are.
These appear to be the top five theories. You pays your money and you takes your choice.
1. The white background exposes dark insects and makes them visible to birds. The birds eat the insects and the tree is freed from predation by crawling critters.
This explanation has a nice green feel to it. Humans are simply helping Mother Nature keep her balance.
2. The second option deals with insects, as well. But a notably darker relationship between man and nature.
The paint is designed to kill insects. We will call this the better-living-through-chemistry option. Dow would be pleased.
The paint is not merely paint. It is latex laced with lime to snuff the bugs — or latex mixed with a sticky substance to trap insects and let them die a lingering death. Like a puma caught in a leg trap.
There is a great divide in advocates of this choice on whether the insecticide option actually works.
3. The third option smacks of a mother’s hand on the cradle. The paint reduces the danger of sunburn in young trees. If the bark is damaged by the sun, it reduces the tree’s natural defense against boring beetles. But not boring creators of painted bark explanations.
4. There is the possibility that one of the other options, in the past, was the reason for painting palm trunks. But, now, the primary reason is aesthetic and cultural. Let’s call it the Ivanka Trump option.
We have come to expect palm trunks to have a bit of makeup — or to look as uniform as a line of Rockettes. Without a lot of kicking.
5. But this is my favorite. There is a tale –undoubtedly apocryphal — that the palm-lined highway in Bermuda from the Officers’ Club was the first to have painted trunks. Apparently, after tackling a full bottle or two of Tanqueray, officers driving home were losing battles with palm trees. And the British military was losing officers.
Some brilliant thinker (undoubtedly an enlisted man) came up with the idea that if the trunks were painted white, the officers might have a fighting chance. Apparently, no one thought of the option of hiding the gin.
I like it because it is such a tidy tale — and has the stamp of authenticy based on my experience with military officers. If there is any truth in it, though, the original story most likely involved a highway safety bureaucrat in Mallorca who had a excess supply of paint for highway lines and could not sell it back to his scoundrel brother-in-law. So, he used it to paint trees.
Even though there is reason to support the highway safety option (you may have already noticed the electricity poles in the second photograph are also painted white), it cannot be the sole answer. Otherwise, why would the trunks of these palm trees on the beach be painted white?
Whoever came up with the Bermuda officer club story would point out that drunks know no boundaries. The trunks are painted white for inebriates who miss their turn and end up driving on the beach.
There is an answer to the question: “Why are the trunks of palm trees painted white?” It is: “How long is a string?”
There are mysteries in life that will forever be mysteries. And this is just another.

Granddad got it right whitewashing tree trunks

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Question: My grandfather always painted the bottom couple of feet of his fruit trees (cherry, walnut, prune, etc.) with a white mixture. I think it was a lime/water mix. (I later heard that a white latex paint is also now used).

That was 70 years ago, as I am now 79.

He said it was for several reasons: 1) It acted as reflector in that it helped protect the bark from cracking from the sun; 2) it filled the cracks and thus prevented a lot of harmful bugs from having homes; and 3) he said it just looked nicer.

Is there any research or studies that you are aware of that might support this? Or is this just an “old grandfathers/wives” tale? His rationale seemed to make sense to me at the time, and I currently do it.

Answer: Your grandfather was a savvy orchardist … and so are you. Whitewashing tree trunks is still an effective method to help prevent sunburned tree bark and protect from damaging boring insects.

Horticulturists from the University of California and Sunset magazine still recommend this tried-and-true technique. This method still is used by professional orchardists. Last spring, I saw whitewashed fruit tree trunks as I drove by many miles of central California orchards.

Even in our more moderate maritime climate, sunburned tree bark is possible in the winter, spring or summer.

During especially cold, clear weather like we had last winter, tree bark is exposed to warm daytime temperatures and direct sunlight. The warmth coaxes the light-exposed tissues out of dormancy, causing them to need moisture. At the same time, the cold temperatures around the shady sections of the tree, including the roots, remain too cold for those parts of the tree to break dormancy. These cooler, dormant tissues are unable to take up the moisture needed by the active tissues.

As a result, tissue may be dead on sun-exposed areas by the time spring arrives. These areas are more susceptible to entry by boring insects and fungal diseases.

Professional orchardists use whitewash to prevent sunburn in young, newly planted fruit trees to prevent sunburn on young trunks. They paint the trunks from about an inch below the soil line to about 2 feet up the trunk.

Whitewash can help prevent boring insects such as beetles, moth larvae and horntails from boring into fruit and nut tree trunks.

And some folks whitewash tree trunks purely for aesthetic reasons. Rows of whitewashed trees make an orchard look clean, neat and attractive.

To whitewash a tree trunk or two in your home landscape or orchard, mix 50 percent exterior white latex paint with 50 percent water. An old-fashioned recipe recommended salt and hydrated lime for whitewash.

For painting rough bark, make the first coat a little thinner than the recipe above, by using more water in the mixture. The second coat can be thicker. Let the first coat dry before applying the second. Stir the mixture frequently as you paint.

Alternatives to whitewashing include wrapping the trunks with paper, plastic or cloth tape. My friends who planted a peach orchard a few years ago protected their young tree trunks with lengths of white corrugated drain pipe, split lengthwise and slipped around the trunk. These materials will help to protect the bark from rodents and deer as well.

White paint protects tree trunks from winter sun-scald

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Have you ever wondered why some trees have their trunks painted white?

The paint is a prevention method for winter sun-scald, also referred to as southwest injury. The trunk is injured when a tree is exposed to intense sun during a season of major daytime and nighttime temperature variation.

The exposure can cause injury or death to the xylem and phloem tissues in the tree. Those tissues are very important as they carry water and nutrients throughout the tree. The damage to the tissue can disrupt the growth and overall health of the tree.

The outcome of southwest injury is evident by large amounts of bark falling off the trunk. Unfortunately, if a mature tree is showing signs, it may be too late. The time to protect against southwest injury is best when the tree is young and the bark is thin and tender.

When painting the trunk, use a white latex non-oil based paint, diluted to half strength with water. Large branches on the side of the sun exposure also can be painted. The paint does not have to be removed during the spring or summer, but probably should be reapplied the next winter.

Once trees mature and develop cork-like bark, they will have self-protection

An alternative to paint is a white trunk wrap that fits loosely around the trunk to allow air circulation. The wrap will need to be removed each spring.

Environmental Studies

White ash (Fraxinus americana), also called Biltmore ash or Biltmore white ash, is the most common and useful native ash but is never a dominant species in the forest. It grows best on rich, moist, well-drained soils to medium size. Because white ash wood is tough, strong, and highly resistant to shock, it is particularly sought for handles, oars, and baseball bats.

The White ash is resistant to heat, although it is native to moist locations, including river bottoms and well-drained upland sites. It grows 50 to 80 feet tall and wide. The trees produce a good seed-set every two to three years and they germinate in the landscape creating a nuisance and perhaps look a bit messy. The seeds are used by many birds and can be produced in countless numbers. The tree grows rapidly and is almost pyramidal when young, but gradually slows down and develops a more spreading round or oval shape. White Ash prefers a sunny exposure where it develops a showy yellow fall color. Fall color can be striking or dull, depending on the tree and environmental conditions.

Physical characteristics

Leaf: Leaflets are often ovate (egg-shaped). The leaves are whitish (glucose) beneath. This tree contains opposite pinnately compounded leaves.

Flower | Seeds: Flowers appear in early spring. These are male flowers. White Ash is dioecious which means the male and female flowers are on different trees. The samaras (fruits) have long, narrow wings. Buds are rich brown with an interesting scaly texture.

Twig: Stout, gray-olive-green, hairless, leaf scars round at the bottom, notched at the top, with lateral buds in the notch; terminal bud is large, brown, with leathery scales and flanked by two lateral buds.

Trunk | Bark: The bark of larger trees usually has diamond-shaped intersecting ridges.

Form: A large tree up to 80 feet tall that typically develops a straight, clear bole (particularly on good sites), usually with a narrow oblong crown.

Life span: Perennial – a plant that lasts for more than two growing seasons.

Ecological characteristics

The White Ash is best grown in moist, organically rich, well-drained loams in full sun. Moderate drought tolerance. Best sited in locations protected from strong winds. Generally tolerant of urban conditions, particularly if well-sited in the landscape. Tolerant of neutral to slightly alkaline soil conditions.

Native Range: White ash grows naturally from Cape Breton Island, Nova Scotia, to northern Florida in the east, and to eastern Minnesota south to eastern Texas at the western edge of its range.

Climate: The climate varies greatly within the natural range of this species. The length of the frost-free period is from 90 to 270 days. Mean January temperatures range from -14° C (7°F) to 12° C (54° F) and the mean annual minimum temperatures range from -34° C (-30° F) to -5° C (23° F). Mean July temperatures range from 18° C (64°F) to 27° C (81° F). The average annual precipitation is between 760 and 1520 mm (30 and 60 in), and the snowfall is from 0 to 250 cm (100 in).

Elevation: White ash grows from near sea level on the Coastal Plain to
3,450 feet (1,050 m) in the Cumberland Mountains.

Soil: White ash has a strong affinity for soils high in nitrogen and
calcium.

Importance to the ecosystem

Seeds of White Ash are eaten by several species of birds. The bark is occasionally food for rabbits, beavers, and porcupines. Cavity excavating and nesting birds often use White Ash. This tree attracts wood ducks, bobwhites, purples finches, pine grosbeaks, fox squirrels, rabbits, beavers, mice, and porcupines.

The damage to the ash population will be economically and ecologically devastating. It has the potential to wipe out the whole species, which could seriously affect ecosystems. In addition, the ash tree is an important economic factor not only by the popularity in the purchase of the tree for ornamental planting but for the products made and sold from its wood. In addition, the cost of removing dead or dying trees is overwhelming municipal budgets. Homeowners must also pay to either prevent the disease or to eliminate diseased trees from their properties.

Relationship with other species

Non-human: White ash is an important source of browse and cover for livestock and wildlife. The samaras are good forage for the wood duck, northern bobwhite, purple finch, pine grosbeak, fox squirrel, and mice, and many other birds and small mammals. White ash is browsed mostly in the summer by white-tailed deer and cattle.

White ash’s ability to readily form trunk cavities if the top is broken
and its large d.b.h. (24 to 48 inches ) at maturity make it
highly valuable for primary cavity nesters such as red-headed,
red-bellied, and pileated woodpeckers. Once the primary nest excavators
have opened up the bole of the tree, it is excellent habitat for
secondary nesters such as wood ducks, owls, nuthatches, and gray
squirrels.

Humans: The durable wood is used to make tool handles, oars, canoe paddles, baseball bats, furniture, antique vehicle parts, snowshoes, cabinets, railroad cars and ties, etc.

Pests: Borers are common on Ash and they can kill trees. The most common borers infesting Ash are Ash borer, lilac borer and carpenterworm. Ash borer bores into the trunk at or near the soil line causing tree dieback. Lilac borer causes swellings on the trunk and limbs where the insect enters the tree. The carpenterworm larvae bore into the heartwood but come to the outside of the tree to push out frass and sawdust. Heavily infested trees can be severely weakened. Keep trees as healthy as possible by fertilizing regularly and watering during dry weather.

Aphids are often seen but are usually not serious.

In late summer, fall webworm covers branches with webbing. The nests in branches close to the ground can be pruned out when first noticed. Bacillus thuringiensis may control fall webworm.

Diseases: A rust disease causes distorted leaves and swollen twigs. Small, yellow, cup-like structures, producing yellow spores, appear on the infected areas. Controls are usually not needed.

A number of fungi cause leaf spots on Ash. The disease is worse in wet years and is partially controlled by gathering and disposing of diseased, fallen leaves.

Anthracnose is also called leaf scorch and leaf spot. Infected parts of the leaves turn brown, especially along the margins. Infected leaves fall prematurely. Rake up and destroy infected leaves. Chemical controls are not practical or economical on most large trees.

Canker diseases cause branch dieback and death of the tree when the trunk is infected. Try to keep trees healthy with regular fertilization.

Powdery mildew makes a white coating on the leaves.

Ash ring spot virus causes chlorotic red and yellowish spots or rings on the leaves. Infected trees may be stunted and dieback, but often the problem in minor.

Verticillium wilt causes branches of infected trees to wilt and die, eventually the entire tree may die. Keep trees healthy and fertilize infected trees to suppress disease symptoms.

Other interesting facts

  • Some of the primary associates of white ash include eastern white pine (Pinus strobus), northern red oak (Quercus rubra), white oak (Q. alba), sugar maple (Acer saccharum), red maple (A. rubrum), yellow birch (Betula alleghaniensis), American beech (Fagus grandifolia), black cherry (Prunus serotina), American basswood (Tilia americana), eastern hemlock (Tsuga canadensis), American elm (Ulmus americana), and yellow-poplar (Liriodendron tulipifera).
  • Almost 99 percent of the fruits (samaras) contain one seed and about 1 percent contain two.
  • One of the earliest reported uses of white ash was as a snake bite preventive. Ash leaves in a hunter’s pocket or boots were “proved” to be offensive to rattlesnakes and thereby provided protection from them.
Sources:

http://edis.ifas.ufl.edu/st261

http://www.gardenguides.com/130390-importance-ash-trees.html

http://eol.org/pages/579138/details

http://dendro.cnre.vt.edu/LandownerFactsheets/detail.cfm?genus=Fraxinus&species=Americana

http://na.fs.fed.us/pubs/silvics_manual/volume_2/fraxinus/americana.htm

http://dendro.cnre.vt.edu/dendrology/syllabus/factsheet.cfm?ID=46

http://www.hort.uconn.edu/plants/f/fraame/fraame1.html

http://plants.usda.gov/java/charProfile?symbol=FRAM2

Page Drafted By: Julia Giza

Why Do People Paint Their Tree Trunks White?

~~ To prevent sunscald / sunburn. Too much hot sun shining onto a tree trunk every day will cause damage to the bark over time. Painting the tree trunk can prevent sun damage.

~~ To protect trunks if a larger tree is removed and no longer provides shade to a smaller tree, or if a large number of tree branches are cut off and the tree trunk is no longer shaded. Only the lower trunks are painted because the upper portion of the tree is protected by the foliage.

~~ To prevent the bark of a tree from splitting and cracking off. This can happen in colder climates when there are freezing temperatures at night followed by a daytime thawing. The painted white trunk helps reflect sunlight during the day and keeps the tree warmer at night.

~~ To protect the bark of the tree from infestation by borer insects. These insects often attack trees with the weakest outer protection. Paint the entire trunk, including dormant buds, and paint the trunk 2 inches below ground in case the soil settles. The trunk of a potted tree should also be painted.

~~ To protect exposed limb stumps after cutting. The exposed areas can sunburn easily and also allow entry for insects and diseases.

~~ To help repel adult beetles and weevils, especially on young trees. Sun reflection off the paint should reduce insect movement across the painted zone.


What to Use to Paint Tree Trunks:

Make a mixture of 50% latex indoor paint or lime, and 50% water. You do not need to use white paint; any light-colored paint will work. Look at the label to make sure there are no additives.

Or you can mix one-third white paint, one-third drywell joint compound, and one-third water, which makes a thicker mixture.

Use a paint brush rather than a sprayer, and one coat is usually enough unless you live in a place with extreme temperatures.

Never use an oil based paint or exterior paint because these type of paints can harm the tree.

If you don’t care for the look of white tree trunks, you can buy tree wrap or burlap.

Cherry trees with white-painted trunks blossom in the street in Jinan, Shandong Province. Photo: VCG

Why are the bottom halves of tree trunks in China painted white?
You may not expect this to be a question that puzzles a lot of foreigners when they first come to China, but it is. Someone even raised this question on the knowledge-sharing platform Quora.
“Why do trees in China have white trunks? Are they born this way?” A netizen asked on Quora.
Every year before winter comes, usually in October, Chinese people begin to paint tree trunks white. It’s common to see people carrying a bucket, a brush or spray bottle, to paint the bottom halves of tree trunks white. But why do they do this?
Global Times reporters hit the streets of Sanlitun, Beijing to see if foreigners share this same curiosity. It turned out that many of them have noticed this phenomenon, but most of them don’t know the exact reason behind it.
“To me, I think they just want to make everything look white,” said Saif Arshad from India. “I mean during winter, there is snow. So white ground, white trees, maybe.”
“I think it’s a sign to show people a message that these trees are newly planted and we should encourage this kind of behavior,” said Jason Lee, a Chinese-Canadian man.
People’s answers varied, but the curiosity is real. Why are tree trunks painted white especially in winter? Is it a kind of decoration or custom only found in China?
Not an exception
If you think only trees in China have this “special treatment,” you’re wrong. Actually some European countries, such as Germany, Greece, and even tropical countries like Panama, do this.
How about people from these countries? Do they know the answer?
“In Germany, we paint trees white to make them visible at night when they are close to the streets,” said Jonas from Germany. “But I think it’s different in China.”
“We don’t have winter in my country, but we also paint trees white,” said Ruben from Panama. “I think they put it on to confuse insects that may eat wood.”
Similarly, many Chinese people share the same idea that the white paint is used as an insect repellent.
Is it the whole truth?
“In fact, people paint the tree trunk white for three basic reasons,” said Cai Ming, a professor at Beijing Forestry University who is a professional in the field of landscape architecture. “One is to repel pests. The second reason is to reflect sunlight and reduce the damage that can be caused by diurnal temperature range. The last reason is for decoration and traffic safety.”
According to Cai, the main ingredient of the “white paint” is quick lime and lime sulfur, which are effective for preventing pests from overwintering and oviposition inside the old tree bark. What’s more, white color can reflect most of the sunlight in winter. So it can prevent the tree bark from getting too hot due to the sunshine during the day and help protect trees during cold nights. In addition, the white color makes the tree more visible at night. It’s not only a decoration, but also a sign to warn people of the street curb.
Improvement expected
“Isn’t it harmful to the tree or the soil?” some interviewees asked.
According to a 2014 report from yuanlin.com, a Chinese website for sharing landscape and forestry information, in some developed countries, people prefer natural methods of pests and disease control. Once a tree is infected by pests or a disease, it will be cut down to prevent the disease from spreading.
“It is what we do in Germany,” Jonas said. “If the situation is really bad and may threaten the whole forest, for example, they cut down trees to prevent moving on.”
“In fact, painting tree trunks white to repel pests was first introduced in Europe,” Cai said. “Previously, European countries applied this technique to fruit trees. But today, most Western European countries stopped using this method while only a few Eastern European countries keep doing this.”
According to Cai, the reason why these countries stopped painting tree trunks is because the main ingredient in the “white paint” – quick lime, is alkaline. If washed off of the tree by rain, it can harm the soil.
As society develops, people’s awareness of environment protection also increases. “Because of this controversy, you can see more and more trees, especially in gardens, parks and campuses, without “white paint” and other methods are being used to prevent these trees from being harmed by pests and disease,” Cai told us. “Today, you can only see these ‘white-trunk trees’ in city streets and country roads, and the function is mainly for decoration and warning the pedestrians and cars at night.”

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