Big Leaf Maple Decline

Asked June 22, 2018, 3:45 AM EDT

I'm looking for an expert in big leaf maples to advise me, I am getting conflicting advice, including from certified arborists. I have a big leaf maple, about 60+ years old, about 10' diameter, and 80+ feet tall. It has experienced some decline as compared to other local trees, the crown has a section which died back. The tree is on an undeveloped area, there appears to be a bot of root trauma many years ago in that one large woody surface root has some bark scars, but nothing has happened on that land in at least 10-12 years other than nearby mowing. It is not irrigated, no flooding, no development, no root zone man made compaction (there are deep clay layers in the soil); yes, summer droughts, I did begin supportive deep watering last summer, no herbicide use.
Cutting that dead wood out has been offered, but the bald eagles love to perch there so I'd like to keep it if that will not harm the tree. The crown is much thinner and lacier in look than other big leaf maples nearby. One arborist suggested cutting back the crown by 1/3- good or bad idea?
The other options I've been offered are to do deep watering during droughts (on it!) and to use injectable fertilizer (24.). In researching online, I see reports mentioning the risks of drilling all those holes and that is a logical concern. Other arborists seem to be against the injectables. I could do fertilizer stakes? Or broadcast surface fertilizer (2-2-2?) having dug holes on a 1x1 grid of the crown.
All the ideas sound 'good' when the person explaining them is the person who believes in them, but I can find flaws in each point. I want to save this tree if possible and would love to find some sort of expertise to help me do that.

Whatcom County Washington

4 Responses

Bigleaf maple decline has been an issue over the past few years in western WA and unfortunately it is still a mystery and pathologists have not been able to identify a cause. It could be related to drought...or not. I don't think you need to do anything at this point. I don't think cutting out the dead wood will improve anything for the tree. Yes, decay can spread--but if you cut it it will still spread from the cut so you haven't gained anything but you've lost wildlife habitat. I'm not a believer in fertilizer for trees like this. Native trees in a natural environment like this should be just fine in the native soil and shouldn't have any nutrition issues.Fertilizer stakes, and especially the inject-able stuff, I consider basically snake oil. That's my take--obviously there are other professionals who feel differently, but they're also trying to sell you something.

Supplemental watering if we get into another extreme drought situation this summer may help maintain tree vigor and certainly wouldn't hurt anything. I'm not sure that it will make any difference, though, and you would need to apply quite a lot of water and it may not be the best use of water in a drought situation. I take a tough-love approach to trees--if they can't hold their own without this sort of intervention, then they weren't meant to be on that site. There are exceptions to this, of course, such as new seedlings that happen to get hit with record drought in a really vulnerable stage. That's just bad luck more than the tree being wrong for the site, so I think supplemental watering is fine if it's practical. Also fruit trees and ornamental trees. It's native trees in their natural habitat that I think should be able to either make it or become a snag for wildlife. That reflects my own philosophy of trees, and yours may be different, especially if you only have a small area with a few trees. So again, just consider this one forester's take on things, and there are other philosophies out there.

Overall, I think this might be the mysterious bigleaf maple decline that we're seeing as opposed to an issue of water, nutrition, or decay. Until we figure out what the cause is, there's not really anything to recommend doing. Even when we do figure out the cause, there may still be nothing we can practically do about it, which is often the case with pathology issues--nature is going to take its course. So my overall suggestion is to take a wait-and-see approach. Monitor it over this year and next, and watch the other maples in the vicinity to see how they do. It's tough to just wait and watch a tree decline. I know if it were me I would very much want to "do something." I just don't think there is anything useful to do at this point, and doing something for the sake of doing something is a waste of money and could make the situation worse.

I hope that helps. Again, this is one forester's opinion.

P.S. As a best management practice, you should keep grass away from the tree--at least outside the dripline and maybe a little further. A good mulch should be applied instead. Also make sure that no herbicides of any kind are applied anywhere near the tree.

Thank you for your well-considered response! I agree with most of what you've said, not that I want to scour the internet to find the people who agree with me, but it makes sense to me that the injections ($300-$400!) are risky and might not help. I can see your point about trees in nature holding their own, but I am willing to help this tree as he is the only tree within 40-80' and is gorgeous, so I would make an exception; however, I don't want to try a bunch of things which result in worsening of the overall condition. Regarding cutting back the crown, I can see the person's point, as the trees along our street which were pollarded in the 60s & 70s do have lush thick healthy canopies, but they are also very unnatural in shape! Thus I am torn as to whether to allow it to be done!

We recently purchased the vacant lot where the tree is, with no plans to develop it. It's been covered with Himalyan Blackberries, buttercup, thistle, and assorted grasses. If I clear those, then a light cover of mulch Like 1-2-3 inches, not 6+?

Maples with dead sections are not uncommon in nature. I think it's part of the tree's beauty, but I'm probably a little odd relative to the rest of the population in terms of calibration for aesthetics--I love the "mess" because it means habitat :)

If it's just sort of that random brushy vegetation, it's probably fine. I was thinking in terms of a lawn. A lot of people have lawn up to the edge of the tree which robs the tree roots of most of the water, and they apply broadleaf herbicides to keep the clover and dandelions away but then wonder why their broadleaf tree is sick, Clearing the blackberries, buttercup, and thistle would be good since they are invasive/noxious weeds. Replacing them with site-appropriate native shrub species is then the long-term solution. I think it's fine if some of those native shrubby species encroach on the tree--that would be how it is in a forest and I don't think it will be much of a competition issue. But it's also fine to mulch for some perimeter of the tree. I would go maybe 4", but keep it back from the tree stem itself--you don't want to pile it against the tree.