By: Bonnie L. Grant, Certified Urban Agriculturist
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.
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.
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.
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.
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A peach tree trunk is painted white with a 50-50 solution of white latex paint in water at the NMSU Agricultural Science Center at Los Lunas. (Photo: Courtesy Marisa Y. Thompson)
Question: Why have some people painted their tree trunks white?
Answer: Have you ever noticed bark buckling off the tree trunk? I first noticed it in a mature mulberry tree in my yard in Las Cruces a few years ago. The bark on the west side of the trunk had buckled so much that huge pieces looked like they were about to fall off.
This phenomenon was likely caused by “southwest injury,” also known as “winter sun scald,” when the tree was young. Southwest injury is especially a problem in climates with intense sun exposure and extreme fluctuations between daytime and nighttime temperatures. In New Mexico, we are familiar with both. If my mulberry tree trunk had been painted in those early years when the bark was thinner and more tender, the buckling southwest injury might not have happened.
Marisa Y. Thompson (Photo: Courtesy)
Retired NMSU Extension Horticulture Specialist Curtis Smith explained southwest injury well in an archived version of this column (access the archives at http://aces.nmsu.edu/ces/yard/archives/). Painting the trunks of trees with a white latex (do not use oil-based paint) is a way to protect the trees from southwest injury.
Phloem and xylem are a tree’s vascular tissues the xylem carries water and nutrients up from the roots to support leaf development and growth, while the phloem carries sugars and other material down to the roots for root growth and functioning. The cambium is a layer of dividing cells (meristem cells) just inside the bark that produces new xylem and phloem. Injury or death of these tissues can seriously disrupt the growth and health of the tree. When you paint the tree trunk with white latex paint (diluted to half strength with water), you reduce the warming of the trunk during the day. White is used because it is not harmful to the tree and is effective at reflecting sunlight to moderate changes in the temperature of the trunk. Larger branches exposed to direct sunlight may also be painted on the sunward side to protect them. Smaller branches may more effectively radiate heat and often accumulate less heat from sunlight, reducing their susceptibility to this disorder.
The trees most susceptible to southwest injury are those with thin bark, including young trees and some species, such as honey locust and apple trees. In most species, as the bark becomes thicker and more cork-like, the trees develop their own protection. Low branches on the south and southwest side of the tree help by shading the trunk, so leave them intact as long as possible. Shrubs or other things shading the trunk can help, too. It is not necessary to remove the paint during the next growing season. As the tree grows and as the paint is exposed to the environment, it will naturally fall away. It is not needed during the summer, but you may need to reapply it next winter.
Another option if you do not want bright white tree trunks in your landscape is a white trunk wrap that is loose enough that it allows air flow and does not dig into the bark. A clear or dark-colored wrap is not recommended. Do not forget to remove the wrap each spring.
The buckled bark of a mature mulberry tree in Las Cruces shows southwest injury. (Photo: Courtesy Angie Swanson)
Southwest injury did not kill my mulberry tree. It continues to provide shade in my old yard in Las Cruces, even with the badly buckling bark, but I know that the tree is not operating optimally and is more vulnerable to water stress, as well as insect and disease pressures, in comparison with healthy trees. For new tree plantings, consider all of the ways you can maximize performance from the start, including the selection of a more drought-tolerant species than mulberry.
Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson
at [email protected], or at the Desert Blooms Facebook page (@NMDesertBlooms). Please copy your County Extension Agent and indicate your county of residence when you submit your question!
For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page at http://aces.nmsu.edu/pubs/_h/.
Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, office: 505- 865-7340, ext. 113.
I started researching the topic and found some interesting benefits if the right paint is used…
In México farmers use Calcium Hidroxide (“cal”) to paint the bottom of trees, especially fruit trees, to protect them against pests and specifically a certain kind of ant, Atta or leafcutter ants.
Leafcutter ants cut and process fresh vegetation (leaves, flowers, and grasses) to serve as the nutritional base for their fungal cultivars. This process can cause serious harm on farms for instance one colony of Atta is capable of defoliating an entire citrus tree in less than 24 hours. Cal is extremely alkaline and ants avoid crawling over it as it “burns” them, therefore protecting trees against the potential damage these ants could cause.
White paint reflects the sun and can protect trees against sun damage especially trees with thin bark, but do consult your local nursery as to the right paint to use.
Paint can also be used to protect exposed tree trunks in cases where the bark has been damaged, this method protects the fragile trunk against pests and further damage until the bark has recovered.
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In "The Garden Primer" (Damrosch), p 422:
Apple borers can also kill the tree outright just by tenneling in through the trunk [. ] Painting the trunk with white latex paint diluted to 50 percent will make it easier to spot the sawdust residue produced by the larvae's tunneling.
Similar advice is in the Fedco Trees catalog they suggest mixing white latex paint with joint compound.
Another danger to the trunk in winter is sun scald [. ]. You can protect younger trunks from winter sun and wind by wrapping them in burlap or painting the trunks with white paint.
This same advice is repeated in "The Backyard Orchardist" (Otto), p43. She actually says to paint not only the trunk, but scaffolds out to nine inches from the trunk.
I'm pretty sure I've seen a mixture of something involving white latex paint to apply to the trunk that is supposed to deter four-legged pests. (I want to say that the recipe had sand in it so that any deer/rodent tasting the bark would get an unpleasant mouth feeling and would avoid the tree, but I can't put my hands on a reference right now. I don't think bone sauce would show up as white.)
Jardins du Mont des Arts. Brussels, Belgium.
After a few swipes on Aunt Polly’s plank fence, Tom Sawyer tired of painting whitewash. So it doesn’t surprise me that there’s no hint, in Mark Twain’s novel, that Tom took a paintbrush to tree trunks.
I have been intrigued with this peculiar cultural phenomenon since I was Tom Sawyer’s age. Yet I don’t see painted or whitewashed tree trunks very often anymore. In the 1950s and 1960s, along rural Kentucky and North Carolina roadsides, you could overlook a few cows and cemeteries, but you’d never miss a white tree trunk.
Rose and I spent 10 days in Sanibel, Florida, with our family, a couple of weeks ago. We packed the car and drove away from Kentucky with a foot of snow on the ground and the temperature headed to minus 15 F
My people and Rufus. Sanibel, Florida.
Along Interstate 75, in North Florida, two days later, with chilly temperatures only in the 40s, we passed mile after mile of beautiful cabbage palms, long needle pines and live oaks that inevitably gave way to endless boring exits, pockmarked with the same national hotel chains and fast food joints. (Confession: I’m a sucker for Cracker Barrel. The chicken and dumplings are scrumptious.)
You rarely find whitewashed trees along any busy interstate highway, though. These landscape artifacts can still be found, off the beaten path, in Florida and around the world. I am surprised and delighted whenever I spot one.
I saw whitewashed trees in Turkey and Greece a few years ago. (We now know that the oracles at the Temple of Delphi were stoned, huffing ethylene poring out of intersecting tectonic faults underneath the temple. However, I can’t confirm that the oracles sanctioned whitewashed Greek trees.)
Stone pines. Ephesus, Turkey.
Sanibel is not exactly filled with stoners. Nor is it swinging South Beach. There’s an old Florida vibe about it. Sanibel is the winter preserve for a lot of vacationing old people. (I am, until the end of my time on earth, stuck in this demographic.)
But there’s more going on here than just old people bicycling, fishing and shelling. The Sanibel-Captiva Conservation Foundation (SCCF) has preserved, with tremendous foresight, 1300 acres of land on Sanibel, Captiva and neighboring Pine Island. They operate a fun native plant nursery, too. I’m still not sure what pushed my temptation button to buy pairs of tender seagrapes and coonties to haul back to a life indoors.
Rose and I love to visit the J.N “Ding” Darling Bird National Wildlife Refuge. We take binoculars and study the birds each time we visit. We forget the birds as soon as we return home. Then we learn them all over again the next time.
We rented a cabin at the Castaways on Sanibel, within walking distance of the beautiful Gulf Coast beach. It turned blessedly warmer.
The Castaways has a special palm grove. I mentioned to a friendly maintenance man just how much I liked his painted palms. He shook his head, raised his hands and claimed no responsibility. His colleague felt more fondly toward the colored trees. He said that you could also find them in Jamaica. A Brazilian landscape worker, it was explained, had previously taken liberty with the white paint at the Castaways.
Stephanie Rose Bird has found a spiritual meaning to whitewashed trees. The author of the Big Book of Soul: The Ultimate Guide to the African American Spirit suggests the color white, as in, whitewashed tree “…represents the ‘other world,’ that is the spirit world from which we conjure energy.”
Besides good energy, there were practical applications for whitewashing, or painting, tree trunks. According to British tree consultant, Peter Thurman, insects might be fended off, and sunscald on tree trunks could be avoided, as well. Plus, the painted trees were more visible along roadsides at night.
But practical seems secondary to tradition.
While we were in Florida I couldn’t stop thinking about Skink, a recurring character in Carl Hiaasen’s popular novels.
Skink, “a ragged one-eyed ex-governor of Florida” and a “renegade,” is not at all cordial to the greed mongers who are laying waste to swaths of Florida.
Observing certain practices when selecting and caring for trees will help to minimize the potential for sunscald and may eliminate the need for painting or whitewashing. Choose plants well suited to the specific site conditions and plant new trees so they are oriented in the same way they were previously grown will help to prevent sunscald.
Drought-stressed trees are more vulnerable to sunscald injury than healthy trees, so water the trees deeply whenever rainfall is inadequate. Cover the tree's root system with a layer of organic mulch about 3 inches thick to maintain moisture around the root system. Finally, gradually thin out a dense canopy or prune to reduce the tree's size over several years to avoid a drastic, sudden increase in the amount of light reaching the trunk.