Our walnut tree seemed to glow in the sun a few days ago, showing off its mossy limbs and growing buds. But, it also showed off its wounds.
This is a pruning cut made by the arborist that I hire to maintain my trees. Every time a tree is cut it leaves a wound. Does the tree heal?
Not really. Instead it grows a ring like a callus around the cut to seal it and prevent the damage or invaders (like fungus) from harming the rest of the tree.
Here is an example of one of my own pruning cuts- and a bad one at that. I cut the branch on my red maple too vertically instead of cutting it at an angle. As a result, it didn’t callus all around the cut and it left the top vulnerable. I keep my fingers crossed that my mistake doesn’t harm the tree!
Here’s another professional cut on another branch on the same maple. What a beautiful callus! And the moss adds a nice touch, doesn’t it?
Thanks for sharing – I didn’t know about that callus ring.
Nice calluses! I find pruning to be therapeutic for the plant as well as the pruner. I try to keep the cuts as clean as possible to avoid fungus, etc. Nothing sadder than a tree brought down by vulnerabilities caused by your own hand.
Does your walnut tree bear actual nuts?
Yes! It actually drops a lot of walnuts- probably hundreds, though I’ve never really counted. The nuts themselves are hidden inside a green mushy mass. My boys and I usually throw them against trees and watch them splat.
Throw them??? Ugh! Just bought a huge bag to use and store for the rest of the winter, much like a squirrel would its acorns. Prized possessions for those inclined toward an omega-rich diet. You and your boys should gather and sell those babies!
Well, first of all don’t underestimate the enjoyment of watching them explode against a tree trunk! But, this is also a black walnut tree, and I don’t think the walnuts are as palatable.
That’s really interesting about the callus, I shall inspect my tree
There is more going on besides the tree growing callus over the outside of the wound. The tree also (and much quicker) walls off the decay with 3 other barriers. One is above and below the wound. One is on either side of the wound. And another one is behind (toward the center of the tree) the wound. Those 3 with the 4th wall formed (eventually) by the callus compartmentalizes the decay where it can’t escape. Improper pruning leaves paths for decay to enter the entire tree. Dr. Alex Shigo discovered and wrote about this ability of trees to wall off decay and said that it actually defines what a tree is. This process is called CoDiT (Compartmentalization of Decay in Trees). You are right that trees don’t actually heal, they just compartmentalize their wounds!
Black walnuts are very good to eat, but stronger flavored than English walnuts. The husk (green mushy part) needs to be removed (careful it doesn’t stain your fingers or clothes) and the main shell cracked. The shell on Black walnuts is VERY hard and you’ll need a hammer or a special cracker to get them open. Then a nut pick is required to get the meat out. It is tedious but worth it!
Thanks for the additional info, Paul! I already know a lot about the green mushy part. My sone and I love to throw them against the trunk and watch them explode! Maybe this year we’ll try to eat some…
I’ve always thought it interesting that there is actually a place on the branch of a tree where it “should” be cut. If you cut along the collar the branch calluses over fine. If you don’t cut along the collar, the callus is hindered in it’s growth.
This tells me that trees were,in some way, designed to be pruned.
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