Hollow Oak - rotted wood inside

[Metcams]

Hello,
I am looking for a little advice on a great oak tree I have in my yard. The tree is hollowed in the trunk and the hollowed out area has rotted wood inside. The tree is very tall and appears to be healthy with full leaves.

Several years ago the tree seemed to be in very poor condition. The leaves were thinning and there were a lot of dead limbs in the top of the tree. It was diagnosed as having construction damage due to compaction and soil being pushed around the base of the tree. After removing the excess soil and several aereations per year, the tree seems to have recovered. The hollowed part of the trunk and the rotten wood has always been there and to the untrained eye, does not seem to be getting worse.

So here is where the situation gets questionable. I had a guy (a cutter but not an arborist) come to look at a tree in the back yard that needed to come down. He called me back and recommended that the tree in the front yard be removed because of the rotted wood in the hollowed part. He then gave me a pretty high price to do the work and I felt he was trying to scare me into hiring him to cut it. Then I had a friend come out who is a horticulturist (not aborists) and he said I should not be concerned about the rotting because the tree appeared healthy otherwise. I am looking for other opinions on the matter. Thanks.

 

[NeTree]

Hollow spots at the base don't necessarily doom the tree. As long as it's healthy, and there is still a good margin (at least 3") of good sound wood, I wouldn't worry much about it. Tell the hack to BS someone else.

 

[MasterBlaster]

If you really want to help the tree out, lay a 6 - 8 in layer of HARDWOOD MULCH down ALL THE WAY TO THE DRIPLINE. Do not use pine bark mulch. Removal of all grass sod is best to do before applying the mulch - it will expedite feeder root growth.
It wouldn't hurt to remove as much of the decaying wood as possible, and apply some type of bug spray to the cavity, and the base of the tree as far up as you can spray it.

 

[mrtree]

If you really care about this tree call in an arborist (preferabbly a consulting arborist with credentials) to do an hazard tree assessment. This will entail not only a visual inspection but in all likelyhood core samples and mathematical calculations. This is far better than simply saying three inches of solid wood will hold a tree. The size and location of the opening and cavity are very important. Get an expert opinion from somebody and don't accept a paragraph on this web board as all you need.


Forget Masterblasters instructions. Mulching with organic matter (including composted wood chips) to a depth of 2 inches is quite appropiate, 6-8 inches will reduce gas exchange (carbon dioxide and oxygen) too much and will large stop any water from entering the soil except in the heaviest rains. Do not remove the grass sod as you will be removing the important feeder roots of the tree also. Kill the grass with glyposhate then apply the mulch.


It would greatly harm removing as much decayed wood as possible. There is clear evidence and countless articles discussing this point. Dr. Shigo's CODIT work is one place to begin learning this most basic knowledge.

 

[Dan F]

I'll agree with mrtree on this one...

Find a certified or consulting arborist (go to http://www.isa-arbor.com and click on the "find an arborist" link) and have them look at the tree.

6-8 inches of mulch is *way* too excessive. 2 inches is marginal though. If you can get between 2-3 inches, that is ideal.

Use a bark mulch (not the red-dyed crap, all that is is ground pallets and wood chips), it will break down easier and quicker, which will help to add organic matter to the tree.

You are familiar with glyphosate whether you know it or not. It's Round-up. And yes, there is no need to strip the sod.


Dan

 

[MasterBlaster]

Whoa, thanks for bringing me up to date on the mulch data - this was how I was instructed by an arborist about 8 yrs ago.
I remember then thinking that was a lot of mulch, but thats what he told me to do.

Was he wrong? Or have changes been made since then?

He said sod removal was necessary to stop it from growing up thru the grass.

The decayed wood removal was all my idea. I've allways done that and I guess I've been wrong. Thanks for the Shigo info, I will check it out for sure.

I love this site!! It ROCKS!!!

 

[Dan F]

Was he wrong? Or have changes been made since then?

He was probably wrong. 6-8 inches will not allow enough water to seep to the roots as well as other things, as mrtree stated.

He said sod removal was necessary to stop it from growing up thru the grass.

I assume you meant mulch instead of grass? If you kill the grass first with Round-up, removal is not needed. Mow it short either before you spray or after it dies, then mulch. If you are worried about weeds, etc, a pre-emergent before you mulch might help, however, if the tree is in a state of decline, I would probably hesitate to use much if any at all for fear of speeding the decline process. If you will want to water the tree (deep and infrequent), a soaker hose under the mulch will aid that.


Dan

 

[MasterBlaster]

What about removing the decaying wood? Is that still wrong? Is bark tracing still okay?

 

[mrtree]

MasterBlaster

You need to go out and get some basic texts. The ISA study guide is very simple, but the references will help. Harris's Arboriculture is also recommended.

Decay removal is NOT an accepted practice.

Your listening to one arborist years ago illustrates a great point. Arborists are not necessarily knowledgable. We are essentially nonregulated and education can be nonexistent or out dated. THis web board (and others) are populated by the same types. Some are horrible, others great.

 

[MasterBlaster]

I most definitely need to update my collection - Shigo's New Tree Biology is the first on the list. Alls I have are basically hands-on types of books(Beranek, Blair, Dent), and no real science/biology material.
I've been meaning(allways loved that phrase) to do this, and since being shown my igonorance on the subject I shall procrastinate no longer!
Thank you, mrtree.

 

[Metcams]

Thanks for all the help folks. I have contacted a local arborist to come out and assess the situation. It seems our county keeps two on staff for just this type of situation.

You all answered my biggest question... is looking at a tree and seeing rotted wood inside the hollow part enough to justify taking the tree down without further investigation. What I heard was no not in itself but with other tests and some knowledge it can be determined whether the tree is doomed.

Again, thanks for the input.

 

[Guy Meilleur]

Originally posted by Metcams
Thanks for all the help folks. I have contacted a local arborist to come out and assess the situation. It seems our county keeps two on staff for just this type of situation.

YOur county has 2 arborists on staff? What blessed land are you in? If they're not certified ask them why not.

You all answered my biggest question... is looking at a tree and seeing rotted wood inside the hollow part enough to justify taking the tree down without further investigation. What I heard was no not in itself but with other tests and some knowledge it can be determined whether the tree is doomed.

The main test is measuring the rotted area, and how can this be done without at least some excavation or drilling, which clearly breaks barriers? All the talk about excavating being NOT DONE is curious--I do it routinely, so I'd like to see the research that finds it harmful, not just opinions by authors.

Thanks for your referrals to research, arborists. And tree owner--be willing to pay a private arborist if the county's guy/gal isn't 100% qualified and convincing.

 

[Kneejerk Bombas]

The main test of how hazardous the tree is, is the target. If it's not likely to hit anything, it's less hazardous.
The next main test is the crown. A tree, statisticaly speaking, is not likely to fail due to decay until 2/3's or more of the diameter of the tree is rotted. The crown of most Oaks will not be full and healthy once this 2/3's threshold is reached.
As for determining what percentage of the tree is hollow, there are noninvasive tools, a simple rubber mallet in the hand of an experienced arborist or fancy sonars, for examples, that can be used, as well as invasive methods like drilling and digging.
If it were a tree located next to a busy daycare, or playground, one where the potential for injury was high, a tool like the resistograph would normally be used. This tools drills a hole and creates a printed reading of wood density.
If it were my tree, I would opt for the noninvasive methods. Unlike Guy, when I go outside and my head gets wet, I think it's raining. I don't need a study to confirm it. Shigo's work on tree decay is exaustive and well documented. Breaking CODIT walls will open an easier route for decay to follow.

 

[Guy Meilleur]

Originally posted by Mike Maas
The main test of how hazardous the tree is, is the target. If it's not likely to hit anything, it's less hazardous.

I agree. No target, no hazard.

The next main test is the crown. A tree, statisticaly speaking, is not likely to fail due to decay until 2/3's or more of the diameter of the tree is rotted.

I agree.

The crown of most Oaks will not be full and healthy once this 2/3's threshold is reached.

I don't agree. I've seen too many trees with >90% hollow that had full, "healthy" crowns. A sugar maple that crushed a car and its driver had virtually NO wood; just standing on bark, yet foliage looked fine. An 8' dia. oak I've worked with for 13 years now is over 90% hollow yet had just minor dieback.

As for determining what percentage of the tree is hollow, there are noninvasive tools, a simple rubber mallet in the hand of an experienced arborist or fancy sonars, for examples, that can be used, as well as invasive methods like drilling and digging.

Is digging out loose rot invasive if barriers are not breached? I don't think so; since the rot is no longer part of the tree's structure, removing it is not invading the tree.

If it were my tree, I would opt for the noninvasive methods. Unlike Guy, when I go outside and my head gets wet, I think it's raining. I don't need a study to confirm it.
Hardy Har Har, cheesehead. Removing rot allows more air and light in which are the enemies of decay organisms. As long as no excessive scraping wounds living tissue or breaks non-living but supportive wwod, what can be wrong with excavation?

Shigo's work on tree decay is exaustive and well documented.
I've read it but don't see the evidence that excavating decay hurts the tree.

Breaking CODIT walls will open an easier route for decay to follow.

I agree absolutely.

 

[Kneejerk Bombas]

The crown of most Oaks will not be full and healthy once this 2/3's threshold is reached.

Originally posted by Guy Meilleur


I don't agree. I've seen too many trees with >90% hollow that had full, "healthy" crowns. A sugar maple that crushed a car and its driver had virtually NO wood; just standing on bark, yet foliage looked fine. An 8' dia. oak I've worked with for 13 years now is over 90% hollow yet had just minor dieback.

When I talk about a healthy crown, I mean from an arborist's point of view. This includes looking at growth increments, leaf color and size, structure, Iodine staining, ect.
Also notice the use of the word "most" in my statement. It is<i> typical </i>of an Oak to start to slow it's growth and dieback above the hollow, and have an inverse growth patter below.
I'm sure you have observed enough trees to tell at a glance, if and where a hollow spot in a tree's trunk is, even if you can't see the original injury.
As a climber, I need to know about the strength of the trees I'm entering. Over the years I have gained a keen sense of how hollow a tree is, and then I often get a chance to test my intuition as I remove the tree and see inside.

Originally posted by Guy Meilleur

As long as no excessive scraping wounds living tissue or breaks non-living but supportive wwod, what can be wrong with excavation?.

Pulling out the fluffy stuff is fine, perhaps even poking softly with a dull tool. What tools will you use that you can insure not breaking that very thin CODIT wall?

 

[Guy Meilleur]

Originally posted by Mike Maas

Pulling out the fluffy stuff is fine, perhaps even poking softly with a dull tool. What tools will you use that you can insure not breaking that very thin CODIT wall?

[/B] Airspade is my first choice if I have the compressor rented. Trowel and perhaps garden hose second unless water would do more harm than good(checking drainage first.
The CODIT wall is typically behind the loose rotted stuff so when I hit semisolid stuff I slow down. The support given by wood in the early stages of decay is something I don't want to remove. Illuminating descriptions of this in Fungal Strategies book; Schwarze goes much deeper than Mattheck et al.

Glad we agree on foliage appearance as indicator of tree health and stability; that'll really fool ya if you don't look REAL close.

 

[Tree Machine]

Excavation of fluff

I almost always opt to excavate, usually starting carefully with the chainsaw, finishing with the scraper (attached). It was a long-standing tool in my woodworking collection. It's actually a cabinet scraper, used to scrape concave surfaces. My Silky Gomboy 300 mm is also in the excavation tool bag.

The fluff inside adds no structural integrity and often is a hiding place for bugs. It also holds moisture and doesn't allow for the cavity to dry out - a sure way to promote further fungal decay.

I don't enjoy excavating, but its classsic tree surgury, and we're tree doctors. I look at the excavations I did 5, 7, 10 years ago and know it was the best thing I could have done for that site. As Mr Maas points out, though, ya gotta be real careful with that adjacent living zone (cambium). -TM-

 

[TREETX]

Re: Excavation of fluff

Originally posted by Tree Machine
I almost always opt to excavate, usually starting carefully with the chainsaw, finishing with the scraper (attached). It was a long-standing tool in my woodworking collection. It's actually a cabinet scraper, used to scrape concave surfaces. My Silky Gomboy 300 mm is also in the excavation tool bag.

The fluff inside adds no structural integrity and often is a hiding place for bugs. It also holds moisture and doesn't allow for the cavity to dry out - a sure way to promote further fungal decay.

I don't enjoy excavating, but its classsic tree surgury, and we're tree doctors. I look at the excavations I did 5, 7, 10 years ago and know it was the best thing I could have done for that site. As Mr Maas points out, though, ya gotta be real careful with that adjacent living zone (cambium). -TM-

I do all of that too but I also fill the cavity with cement to add integrity or just fill the cavity with foam. After that is done, I usually install 10-15 cables to ensure that ever limb is secured. When cabling, I make sure I use those bent, non forged lags from Home Depot.

I say just leave it alone. Let decomposers do their thing. Focus on the living part.

 

[Guy Meilleur]

Re: Re: Excavation of fluff

Originally posted by TREETX
I say just leave it alone. Let decomposers do their thing. Focus on the living part.

I agree that most of our attention should be on growing the tree, but that includes discouraging things that kill the tree, doesn't it?Decomposers kill the living parts, so some of the focus should be on weakening them, as we strengthen the tree.

I don't understand the cabling/overkill reference as analogous to excavation of decay. One damages the living parts, the other acts to preserve them.

 

[NeTree]

I think everyone is missing something!

When dealing with hollow spots at ground level, the tree is more likely to uproot from lack of anchoring roots than fracture at the point of decay. A thorough root inspection is wise! If the tree is salvageable, then on to the next step.

Although foam is relatively impervious to insects, it tends to trap moisture that can accelerate decay even further. It also adds little to strenth to the structural integrity of the affected area, and looks god-awful in a few years when it turn that icky-brown and gets mouldy.

Cement can add great strenth, but when the time eventually comes to remove the tree, it can be a major hazard to chainsaws and the person doing the removal. Cement also traps moisture that than further the decay.

So.....

What I have been doing for years that works exceptionally well is:
1) Gently scrape away any loose debris in the hollow to the CODIT wall.
2) Mix up some fibreglass epoxy resin. DO NOT ADD GLASS!
3) Thoroughly coat the affected area with 2-3 coats.

Why the resin?
a. It bonds to and with the rotten fibres and creates a tremendously strong layer of support that adds structural integrity.
b. It's waterproof
c. It will cut with a chainsaw without operator harm.
d. Impervious to insects and won't support mould.
e. The tree can compartmentalize over it
f. It looks better than foam, and is about the same price.