My girlfriend and I recently drove through Arizona, and while most of it was desert, we did see a few orchards of citrus trees. However, it was odd to see that many of the tree trunks were painted white. I was curious to learn more about this, so I did a bit of research. Here’s what I found.
Citrus tree trunks are painted white to reflect sunlight off the tree’s bark in the winter season. This prevents the tree’s sap from entering a thaw and freeze cycle that might damage the tree’s tissues. The reflective paint also keeps citrus trees from becoming sunburnt in the summer.
So, using white paint on your citrus trees helps prevent damage to their tissue and trunks in the summer and winter, but should you paint your trees? If so, what’s the best way to paint them? Let’s take a closer look.
Should You Paint Your Citrus Trees White?
Consider painting, or “whitewashing”, your citrus trees if you live in an area that gets cold, dry, and sunny winters. The white paint will help protect the tree during extreme heat in the summer, and the freeze and thaw cycles in the winter.
To determine if you should paint your citrus tree trunks white, it’s helpful to know a bit about what happens to citrus trees during freeze and thaw cycles.
Citrus tree painting is most common in desert areas like Arizona or in parts of California that have a higher elevation, where the temperature difference between day and night is enough to throw off the tree’s sense of dormancy.
To better see how warm days and cold nights can damage a citrus tree, think of how you use hoses during the winter. During freezing weather, hoses generally need to be drained of all water. If there’s water left inside, the hose will expand and rupture the hose from the inside-out. The same can happen with citrus trees.
When it’s warm, citrus tree sap normally moves up and down its tissues. However, during freezing weather, the flowing sap will become stuck from the cold. It also expands as it freezes, which bursts plant cells and tissues.
Because of this, the citrus tree could then crack or split, which exposes the tree and increases the risk of pests or disease from bacteria or fungus.
Trees can also become dehydrated and stressed by the lack of flowing sap, as the cold and dormant roots won’t provide water or nutrients to the active tissues.
This stress from infection or dehydration can stunt the citrus tree’s growth or fruit production for all of the next growing season and beyond.
So, where does white paint come in?
White paint reflects the strong winter sunlight off of the citrus tree’s trunk and prevents the tree from warming and waking up from its dormancy. By keeping the tree’s temperature lower during the warm days, the freezing nights aren’t as drastic. This prevents the tree from going through extreme internal temperature swings and protects the tissues from bursting.
Because of this, the tree remains stable and in a sort of stasis throughout the dormant, winter season.
What Else Does White Paint Protect a Citrus Tree From?
Whitewashing a citrus tree when it is young also protects the thin bark from sunscald damage, which is caused by the strong sun beating directly onto the tree bark without the protection of foliage or other shade. It’s essentially a sunburn for trees.
Also, painting the trunk white adds another layer to the thin bark that can help with light physical damage, like something hitting or scraping the trunk.
Some orchardists also rely on the painted bark to help them spot borers, as their sawdust trails show up more easily on the white paint than they do on the plain bark of an unpainted tree.
Is Paint Bad for Citrus Trees?
The paints used by gardeners or orchardists are usually a lime-based whitewash or a latex-based paint, which don’t harm the tree, although there are drawbacks to the latex paint (more on this below).
The white paint is applied to the outside of the bark, which is itself a shield or barrier for the tree’s inner tissues, so there’s little to no absorption in the tree.
However, not all paint is safe for use on trees. Oil-based, enamel, semi-gloss paints, and paint primer should never be used, as these penetrate and stain the bark of the tree.
What Kind of Paint Is Used on Citrus Trees?
The best paints to use on citrus trees are:
- Whitewash (also called limewash)
- Casein paint
- Latex paint
Let’s take a look at some of the pros and cons of these paints and see which one is best for citrus trees.
If you’re painting your own tree, you may want to consider avoiding latex-based paint.
The latex in paint, even in indoor grades, is derived from petrochemicals. This means they produce fumes known as volatile organic compounds (VOCs) that cause respiratory harm to life that’s close enough to inhale them, and its run-off contaminates groundwater.
Fortunately, there are safer, organic alternatives.
Limewash is a type of whitewashing, and one that specifically uses, you guessed it—lime. It’s an old term for white paint made with hydrated lime, or calcium hydroxide.
The process of manufacturing limewash involves taking limestone and treating it with heat and water to change its chemical makeup. It’s also considered an environmental, or green product.
To make limewash for your citrus trees, you’ll first need ten pounds of crushed lime. Start by adding three pounds of salt to twelve quarts of water, and then slowly add the ten pounds of crushed lime, stirring as you go.
However, if DIY isn’t your thing, check out the selection at limeworks.us.
White paint made from casein, or milk proteins, is easily made at home and is another good alternative to white latex paint.
To make casein paint, add the juice of one lemon to a quart of skim milk. Leave this out overnight. The next day, strain out the curds with a sieve or cheesecloth. The curds can be pulverized and used as paint or, to make their color even whiter, combined with four tablespoons of dry artist’s pigment.
How to Apply White Paint on Citrus Trees
It’s best to paint citrus tree trunks in the early fall before things start to get really cold, but if you’re already in the winter season, apply the paint on a warm day. All you need is your whitewash of choice, a paintbrush, and a plan.
Here are some more tips on how best to apply whitewash citrus trees:
- Whitewash young citrus trees as well because their bark is still thin and can be easily burned by the sun.
- Plan to paint in the morning when the outdoor temperature is 50ºF and rising. Do it as early as you can to give the paint time to dry before nighttime and the cool temperatures arrive. But if you do it too early while the air is still cold, the paint itself may freeze on the trunk, which defeats the purpose. So plan accordingly!
- A normal paintbrush is really your best bet for whitewashing. Some people like to spray the white paint onto the trunk, but this makes good coverage difficult, especially if there’s a breeze.
- If you’re using casein paint, use it as soon as you can after you’ve strained it. If you wait too long, the paint will spoil and be very unpleasant to work with.
- Apply the paint from the base of the tree up to where the trunk splits into branches. If you’re painting a young sapling in spring or summer to protect it from scald, paint it up to the point where the foliage begins shading the trunk.
- Paint all sides of the tree, not just the southern exposure.
- If you’re using limewash, keep stirring the paint pretty frequently as you go along to keep the lime fragments suspended in the water, or to keep the milk proteins from separating.
- The trunk will need two or three coats of paint to get good coverage and color.
- Refresh the paint on your citrus trees once a year in the fall, and you’ll have thriving citrus trees for many years to come.
If you’d like to learn more about whitewashing, here’s a video by Enjoy Transformation that shows how to make a traditional limewash.