Question: I lost about 1/3 of my crabapple tree and probably more than 1/2 of a mimosa tree in the wind storm on Tuesday. Is there anything I should do to try to help them?
Laura P., Albuquerque
Answer: Great question! The short answer is, "No, at least not urgently, and there’s no need for any type of wound sealant." For now, in case it helps you rest easier, imagine what your trees would do if they were all alone in the forest and were damaged by wind gusts. They'd just sit there and be fine. That is, unless there are any immediate risks, like a car parked underneath or an area of high pedestrian activity nearby where a partially broken limb could fall and hurt someone.
Aside from considering bodily harm and property damage, the next step mostly depends on how bad the damage was. How thick were the branches that were broken? How many branches, approximately, per tree? And are they within easy reach from the ground?
Evidence from tree research performed all over the world has confirmed that clean-cut wounds (as opposed to scraggly, jagged tears) seal better and faster. Trees’ natural responses to injury are partly influenced by the time of year and the growth stage; for example, responses may be faster in the active growing season than in the dormant season. In the coming weeks, you or a trained arborist can clean up the jagged branch breaking points to help the trees seal those wounded areas more easily. It is very important that the wider base of each branch (called the branch collar) be left intact so that the cambial layer just inside the bark can grow over the wound to seal it.
As I wrote in a pruning column in what seems like forever ago (January), “Tree wounds never heal. They can seal, but only if cut properly. At the base of each branch, where it meets the trunk, there is a special area called the branch collar. Think of the trunk as wearing a short-sleeved shirt with the sleeve bunched up (branch collar) and the branch as the arm extending out of the sleeve. The tissue in the branch collar (bunched sleeve) is capable of sealing a clean-cut pruning wound, but only if the entire branch collar is in place. This means that there will be a bump on the trunk after pruning, but at least it will seal. If a flush cut is made, there will not be enough collar to seal the wound. Often, the branch collar is observable, but even if you can’t see it, you should try to visualize it so that you are sure to leave the branch collar tissues intact. Don’t nick the collar.” For more details on recommended pruning techniques and additional resources, go to https://nmsudesertblooms.blogspot.com/2020/01/pruning.html.
For management strategies specific to those two trees (crabapple and mimosa) that were damaged in your yard, I reached out to other experienced arborists for advice. They agreed with my recommendations and added several things to consider.
Retired NMSU Extension Horticulture Specialist Dr. Curtis Smith boiled it down to these two choices for each tree: “Replace or retain. When the damaged branches are properly cut (clean cuts at the best location or just beyond the branch collar), will the tree look good enough to keep or would a new tree be a good idea? From the size of the branches in the photo, I think hiring an ISA-certified arborist is a wise choice.” (ISA stands for International Society of Arboriculture, and certified arborists are listed on their website: https://www.treesaregood.org/findanarborist.)
Joran Viers, City Forester for the City of Albuquerque, responded, “I agree. If the canopy is worth keeping without those branches, they could be more cleanly removed and a nice living edge of cambium exposed, which should have some potential to form wound wood and perhaps in time strengthen the damaged area. Of course, decay is likely to occur in the interior of the limbs at the breakage or pruning site, but that is just nature, and what are you gonna do?” We know that pruning sealers do not prevent decay on tree wounds, and they can even encourage bacterial and fungal growth. Viers added, “As small as both trees are, I would try for cleanup and restoration of both of your trees—worst case scenario is they fail in a few years, but neither has much target to worry about.” In the world of arboriculture, a “target” is any person or property that could be in danger if a tree or branch falls.
Wind gusts in the storm system that blew across New Mexico earlier this week broke a lot of branches and even toppled entire trees. The Albuquerque National Weather Service tweeted, “Strongest east canyon winds since at least 1987. We had 71 mph gusts here at the #Albuquerque Sunport!” (@NWSAlbuquerque). To see photos of other damaged trees and a video clip by Albert Torres in which he shouts “Timber!” as a honey locust tree hits the ground, visit the blog version of my column at https://nmsudesertblooms.blogspot.com/. I’ll include a map showing rainfall data collected today from CoCoRaHS volunteers all over the state. CoCoRaHS is an acronym for Community Collaborative Rain, Hail & Snow Network. This amazing citizen science network started 20 years ago at Colorado State University’s Colorado Climate Center and now has over 20,000 active observers in the U.S. and Canada. Spoiler alert: Doña Ana County won the prize for the highest amount of rain at 1.68 inches.
Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at firstname.lastname@example.org, or at the NM Desert Blooms Facebook page (@NMDesertBlooms)
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For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms (http://desertblooms.nmsu.edu/) 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.