Saturday, December 16, 2006

They Don’t Bite. They Don’t Even Light.

No, I’m not talking about mosquitoes, it’s powder post beetles. And I guess that’s not entirely accurate, because they do bite a little. When I removed the finish floor in the bathroom I found evidence of some beetle damage. It was very limited because they only eat the sap wood and not the heart redwood.

The sap wood is the outer inch or two of wood on a log. As I understand it, this is the part of the tree that is still living and growing. The sap wood supplies nutrients to the upper reaches of the tree. The sap wood is white or yellow in color. The heart wood is the red wood in a redwood tree. It is the tannic acid in the wood that gives it it’s red color. This also makes the wood unpalatable to the beetles.





Notice in the shots above how the beetles devoured the sap wood but left the redwood alone. I have a 15-foot 6X6 beam in the garage that I salvaged from the addition. It has a thin vein of sap wood running along one of the corners. Just as in the board above, that thin vein of sap wood is gone and the rest of the beam is untouched.

This is why I go ape poo-poo over redwood, and why I get so steamed when people knock down the old buildings around here and grind the wood in to saw dust. Even pressure treated wood has it’s failings because the chemicals don’t penetrate the piece of wood after a few inches. If you cut a piece of pressure treated wood, and expose the center, it must be retreated or you have given the bugs an opening.

3 comments:

purejuice said...

great pix, thank you. is heart redwood the only stuff they don't eat?

Greg said...

I'm not sure really. I think cedar is another bug resistant tree, and maybe mahogany. I do know that other trees have tannic acid, or tannin in the bark, seeds, and wood. Maybe it's just not in as high concentrations as in redwood. I'm hardly an expert. There is the Tan Oak that has tannin in the bark and this was used in tanning leather. West coast Indians eat acorns, but the tannin must be leached out of the nut before it is processed.

Angus said...

I've often wondered if you can treat wood with tannin to prevent beetles?
(Could stir your morning tea with a 2x4 every day and ... hmmm).