Painting the trunks of young fruit trees with white water-based latex is one of the most important things you can do for them in cold country, and one of the cheapest. It takes a few minutes a tree. Skip it and you can lose a tree you did everything else right on.
50/50 white latex and water
Ground up to the lowest branches
Going into winter
Why it matters
What Sunscald Is
On a sunny winter afternoon, the sun hits the south and southwest side of the trunk and warms the bark way above the air temperature. The living tissue under the bark starts to wake up and loses some of its hardiness. Then the sun drops behind the hills, the bark temperature crashes in minutes, and that tissue freezes and dies. Some folks call it southwest injury.
You usually don't see it until spring or summer. It shows up as a sunken, discolored, cracked or peeling patch of bark on the southwest side. On a young tree it can kill a big share of the trunk, and the dead patch is an open door for borers and canker. Snow on the ground makes it worse, since it bounces even more sun onto the trunk. Warm chinook winds on top of that sun push the bark temperature around even more.
That's why this is super important. A tree can be plenty hardy to your coldest night and still get hurt by a sunny afternoon followed by a cold evening. White paint turns enough of that afternoon sun away to keep the bark from waking up.
Growing under a high tunnel? It's likely worse in there. The tunnel hands you the hot afternoon and gives you nothing back at night. Paint those trunks too.
Low winter sun comes in from the south and southwest, and snow reflects more of it onto the trunk.
Which trees
Which Trees Need It
All young fruit trees. Thin, smooth bark is the most at risk, so pay extra attention to cherries, peaches, nectarines, apricots and plums, but young apples and pears get it too. Keep painting until the bark thickens up and the canopy shades the trunk, which takes several years.
The recipe
The Mix
50% white latex paint to 50% water. Interior latex, thinned about half with water. Stir it well.
Water-based latex only. Never use oil-based paint, enamel, or anything with solvents in it. Those can damage the bark.
White only. The whole point is turning the sun away. Any other color absorbs more heat.
A gallon of paint makes two gallons of mix, which goes a long way on young trunks.
Timing
When to Paint
Get it on the trunks going into winter. We tell folks to do it in early fall, right around when they stop watering to let the trees harden off. You can also paint right at planting in spring. Pick a dry day that's warm enough for latex to cure (most cans want about 50°F or warmer, so check yours) with no rain coming for a day.
How to
How to Paint a Trunk
Pull the mulch back from the base of the tree so you can get right down to the ground.
Brush off loose dirt and anything flaking off the bark.
Stir the mix. The paint settles, so stir again every so often while you work.
Paint from the ground up to the lowest branches, or at least 2 feet up on a whip. Use a 2 to 3 inch brush, or a garden sprayer if you've got a lot of trees. Go all the way around the trunk and give the southwest side a good coat. Painting over the graft is fine.
Let it dry before you push the mulch back or put a guard on.
Touch it up going into each winter while the tree is young, wherever bark starts showing through. The trunk grows and the paint wears, so new bark comes in bare.
Pair it up
Paint Plus a Guard
Paint does nothing for rodents. Voles, ground squirrels, pocket gophers and rabbits can still girdle a painted trunk. Paint first, let it dry, then put on a 1/4" hardware cloth guard. The wire lets plenty of light through to the white paint, so the two work together.
Not water-based latex. It lets the bark breathe and wears off over time. Oil-based paint is a different story, so don't use it.
Why does it have to be white?
White turns the sun away, so the bark stays close to the air temperature instead of heating up in the afternoon. That's what prevents sunscald.
How high should I paint?
From the ground up to the lowest branches. On a whip with no limbs yet, go at least 2 feet.
Should I wrap the trunk instead?
We've moved away from recommending tree wrap. The benefit is real but very marginal, and paper or crepe wraps aren't worth it. Paint is the better bet. The only wrap-style protection worth doing is a rigid cylinder with an air gap that lets ground heat rise around the trunk, which is what a hardware cloth guard gives you anyway.
Do older trees need it?
Once the bark is thick and the canopy shades the trunk, sunscald is much less of a risk. Young trees are the ones to paint for the first several years.
What about trees under a high tunnel?
Paint them. The tunnel makes the afternoons hotter without keeping the nights any warmer, so the swing is likely worse in there.
Not sure what to plant? We'll pick your trees.
Tell us about your place, your goals and your budget. We'll pick what fits, build the order for you and email it over within 1 to 2 days.
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