Great Stuff to Fill Cavities  

TOPIC: tip: Great Stuff to fill cavities

== 1 of 1 ==
Date: Mon, Aug 4 2008 8:41 am
From: Kirk Johnson

I have an old red maple in my yard, that when I moved in seven years ago had
a lot of old dead and rotten branches and cavities from previously rotted
out branches, etc. Not too unusual, for those familiar with red maples.
Obviously no one had ever really taken care of this tree or kept it pruned
properly. I decided to try to save it.

There were at least a half dozen cavities. I trimmed off excess material
around the cavities neatly with a pruning saw, scooped out rotted wood and
debris from the holes, then took a can of Great Stuff expandable foam
insulation and filled the holes. After it dried I trimmed off the excess
foam flush with a utility knife, then painted over the whole thing with
shellac to try to seal out water.

Three years later the tree is still alive and is slowly healing over all the
cuts. So far so good. It's not a very happy tree because it's right next to
my neighbors driveway which they've dug up a couple times over the last ten
years to replace water & gas lines. But it might live. I fertilize it every

So if you're looking for a way to fill cavities in trees, Great Stuff seems
to work pretty good. Thought I'd share.

Kirk Johnson

== 1 of 2 ==
Date: Thurs, Aug 7 2008 5:45 pm
From: "Edward Frank"


The use of expanding foam sounds like a good option. I am just wondering about the downside of the application if any. The foam would expand to block the hole with a very lightweight material. There is no problem of getting it to stick to the surface because it forms itself to the shape of the hole in which it is placed.


----- Original Message -----
Sent: Thursday, August 07, 2008 8:08 PM
Subject: [ENTS] Re: Anaerobic

My general impression from the arborists I dealt with while at Grand Canyon, was that the tree itself provides the best means of sealing itself off, ie, the passage of sap hitting air, congealing and eventually getting grown over.
It was thought for some time that applying some kind of tar, or other high viscosity/sticky substance would serve to prevent bacterial/fungal infection, but the tree's natural response to exude sap/pitch often made such an application ineffective.
I have seen trees where large openings were filled with cement, and lived, but I suspect many more died with such treatment.

== 2 of 2 ==
Date: Thurs, Aug 7 2008 11:42 pm

I don't know much about the expanding foam, although I'd want to know a little bit more about its chemical nature before use...another consideration might be the not insignificant forces that a tree's structure can exert, and would the expanding foam be up to the task. Otherwise it has good features (I have seen how it expands).

== 2 of 2 ==
Date: Fri, Aug 8 2008 5:22 am
From: Kirk Johnson

I agree that the best scenario is to simply let the tree heal itself,
especially if limbs have been pruned off properly and there is little to no
rot involved. However, this particular red maple looked to be well past a
'tipping point' that it wasn't going to recover from without outside help.
Thus the artificial means of filling the cavities, and sealing over with
shellac. I used shellac because that's what we used to use in special
situations when I worked for an arborist two summers when I was in college.