There’s a lot of plant physiology in my message today. It involves ways we can make our trees sick by our own careless management. I’m going to confine my comments this time to what we do to trunks and branches. We’ll save leaves and roots for another time. Check through these issues to be sure you’re not guilty.
Woodpeckers and sapsuckers. We’ll start off with the least threatening among them. We have a couple of bird species whose occupations or hobbies are pecking holes in the trunks of trees. Usually the holes will be in regular rows, looking like machine-gun spray across the trunks.
Their activity seldom suggests presence of damaging insects, so there’s probably nothing you need to spray. Their “damage” is usually minimal unless they persist in riddling one particular branch or tree trunk. In most cases they’re coming back later to feed on the sap that exudes from their wounds.
If you’re concerned, I’d suggest starting with an application of pruning sealant spray. If they continue, move to paper tree wrap from the ground up to the lowest limbs. Otherwise, no harm, no foul.
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Borers. These are larval forms of beetles and moths. Each insect species will have a particular host species of tree that it attacks. That’s why it’s so critical to know with certainty what type of tree you are growing.
Unfortunately, our borer prevention and control remedies are now pretty minimal.
Unfortunately, our borer prevention and control remedies are now pretty minimal. We used to have insecticides that could be applied to the bottoms of trunks in late August to stop development of peach tree borers, but they’re no longer sold. We’re back to old remedies our great-grandparents used.
However, keeping your trees healthy and vigorous and perhaps wrapping their trunks while they’re young will still be your best means of coping.
Sun scald. Some of our young trees have very little bark when they’re bought at the nursery. Shumard red oaks, chinquapin oaks and Chinese pistachios all have very thin bark. They’re grown closely together in their original nurseries, but then are suddenly exposed to Texas’ hot, baking sun.
Damage shows up on the south and west sides of the trunk. Bark starts peeling off a year or two later, and borers move into trees that are normally not prone to them.
Solution: Wrap the trunks of new trees with paper tree wrap, available from local nurseries and hardware stores.
Line-trimmer damage. For fear of vandals, for many years I was reluctant to say what follows: You can kill a tree by making a single knife slit completely through the bark and cambium layer at one elevation on the trunk. That severs the phloem tissue that conducts manufactured sugars from the leaves to the roots. The roots die and the tree dies.
Many a fine tree has been killed in just a few minutes by this careless and senseless act.
That phenomenon became very widely known when aggressive lawn maintenance workers started cutting through bark with their line trimmers. Many a fine tree has been killed in just a few minutes by this careless and senseless act.
Use a trunk guard, or better yet, aim the trimmer down to the soil and maintain a 2-inch ring of bare ground around the trunk.
Girdling trunks. This is akin to the big guy with the 44-inch waistline trying to squeeze into his 34-inch jeans. It’s not going to end well. When we wrap a wire, fencing, chain, nylon twine or any other rot- and decay-proof line around the trunk or branch of a tree, and then forget that it’s there, the internal wood of the tree can grow out and around it.
That’s not a huge problem initially, but eventually it will sever the critical phloem tissue just like the line-trimmer damage above. The entire top of the tree will weaken, dry and perhaps even break.
Root flare. I said I’d talk about root damage another time, but this actually plays in with the trunk. When we plant a tree too deeply, either by initial choice or because the tree’s soil ball sank, the trunk ends up too low for its planting site. The tree is stunted and perhaps even eventually killed.
You should be able to see where the trunk flares out like the delta of a large river as it enters the ocean.
The solution? Expose the root flare. You should be able to see where the trunk flares out like the delta of a large river as it enters the ocean. You want to see that root flare.
Mulch volcanoes. That’s the “highly technical” term used to describe the strange formations of mulch 10 or 12 inches up our trees’ trunks. In reality, these usually seem to appear around trees in quickly installed commercial landscapes, and a landscape contractor friend of mine pointed out that those were trees that were planted probably slightly above grade (on the ruse that they needed perfect drainage).
He added that the crews were probably too lazy to carry the soil they had just taken out of the holes, so they just concealed it with mulch.
That’s just wrong at all levels. A tree needs to be planted at the same depth at which it was growing in the nursery row or pot. An inch or two of mulch to conserve water would be fine, but not multiple inches of mulch that must be replenished annually lest the secret be known.