Question

Tree Hole   QUESTION: Jim,
I have a large Oak tree that is primarily horizontal in its growth direction and it has a huge hole in the "top" of it, filled with quite a bit of water.
We bought this house in April of 2009 and it has been that way obviously for a long time. I have read about filling with concrete or foam and both seem to have issues but this is a huge hole and has probably 3 or 4 gallons of water trapped inside. If I'm not going to fill it, can I drill a hole through the bottom to drain the water out? I know, another "wound" but that much water is not healthy either. As you can see from the first photo, this is a big tree- probably 24" in diameter at the location of this cavity. I'd appreciate your suggestions or confirmation that a hole drilled from underneath would be the best way to eliminate the problem, even if I don't fill the cavity with anything. If I did fill the cavity, I would make a sizable bead of silicone caulk on the edge of the hole to allow for movement before using newspaper and foam to fill the hole and of course sealing that with wound spray.
Thanks for your help with this, and have a blessed day!

ANSWER: Traditionally, homeowners have attempted to clean decay from the cavity and to add a material, such as concrete, to fill the empty space. Cavity treatment is an exacting process that if done incorrectly can shorten the life of the tree. The hard rim of tissue surrounding the decayed wood must not be broken or decay could spread to the wood produced after the initial injury. If you chose to remove decayed wood, only remove wood that comes out easily.

Benefits from filling the cavity are questionable at best. Since the fill material will expand and contract at a different rate than tree wood it can create problems of its own. The strength of a hollow tree comes from the new wood produced after the injury, not from material used to fill a cavity. Remove hollow trees that appear weak and are likely to fall.

Sometimes the cavity will contain water. The old recommendation was to drill holes below the cavity so the water could drain. However, drilling holes will break the barrier that keeps the decay from invading healthy wood. If water has been present for one or more growing seasons, the tree has already adjusted. You can cover hollow openings with a piece of tin or window screen filled with plaster to keep out animals, water, and to form a surface that allows new tissue to grow over the opening.

When a tree is wounded, it uses its natural defense of compartmentalization to create a barrier between the wound and the rest of the tree. Recent research shows that it is better to leave the cavity open and take the necessary measures required to improve the overall health of the tree. A healthy tree has the strength to compartmentalize and wall-off decay.


Here is some information on a hollow tree.
The heartwood consists of the growth rings in the center of the trunk. They are aged sapwood and thus form part of the Xylem. They tend to have a darker color than the sapwood, because they no longer transport any water and are therefore much drier, and they tend to be clogged up with gums, resins and other substances, depending on tree species. Because they are no longer taking part in the trees vital processes, they can be said to be 'dead wood'.
A hollow tree is a tree where the heartwood, which has less resistance to rot than the living parts, has gradually decayed away. Surprisingly, this makes no difference to the vigor of the tree and may even enhance it ability to stand up to severe gales, due to the immense strength of a tubular structure. So it is important to realize that a tree with decaying heartwood is NOT a decaying tree! It is a natural process in many older trees and makes them all the more valuable as a habitat for many different forms of wildlife.  





---------- FOLLOW-UP ----------

QUESTION: Jim,
I didn't get an answer I can use to make a decision from you, but you can't see my tree!

This is a huge hole and does have a lot of standing water in it so it does not create any habitat for other critters and the water is NASTY. The hole has obviously been there for many growing seasons, and although it's hard to see, there is another hole visible on the otehr side of the tree, but it is above the water line. I still think drilling a hole from the underside to allow drainage would be better than doing nothing, or maybe trying to get some small pump and remove the water. My Jack Russell used to run up the tree (it is pretty horizontal) and would stick his head in the hole but would quickly snort because the smell of the water was so bad and continue to run up the tree, one time after a raccoon.
I don't want to lose the tree and would think that my idea of a LARGE bead of silicone caulk to line the edge of the hole before carefully sealing it would be ideal. Have you ever seen that process done and was it successful? This tree doesn't move much with the wind as it is 24 inches in diameter at this point, and it is next to an upright oak that is even larger and "protects" it from the higher winds. If I drain it, would the tissue underneath be more suseptible to rot?

Thanks again for your help with this.
Of course I'll give you a great rating whether I agree with you or not, especially for your quick response.

I am a State Certified Master Gardener and owned a Landscape Company for 5 years but that was 20 years ago.

Answer
Your case is unusual and I think I would try draining the water with  a hole drilled low in the cavity. Cement will stay hard and will rub the cells on the inside causing more decay. You might trey spray installation foam. This is used in walls to fill spaces. It is sprayed in as a liquid but hardens but still has some give to it not like cement. If you did this I would stop about near the edge of the hole where the bark is smoother--this is were the tree is trying to grow cells over the wound. But in your case the hole is too large. Filling it to this point can allow the tree to try to heal over the wound. This installation should harden enough to keep out moisture. I do not know if it needs to be dry inside or not before you treat.

I would try draining the water then let it dry somewhat and apply the foam. May try contacting a building contractor in your area to see if they know anyone who uses the foam as installation and what they would charge to fill the hole. Maybe able to get them to use some left over foam from a contract and this maybe less than a special job. They do make this in aerosol cans BUT it would take a great deal of cans and would get expensive.  Here is a web link to a discussion on foam in house walls but the principle should about be the same. http://www.rlcengineering.com/sprayfoam_091908.htm

I have read that is has been done with the foam but have never seen it. Let me know how it works out. Good Luck!