In article ,
"doug" writes:
|
| Further, - the least rot was always in the bottom end below ground level.
| That was because some of the preservative (creosote) had leached down,
| through the long years, and soaked the full length and width of the stub of
| the pole.

That's actually not the reason.

You can observe it with treated or untreated timber. The fastest
rot is AT ground level, followed by the top of the pole (if uncapped,
but not if capped) and then either the above- or highish below-
ground sections (depending on the wood and conditions). The very
deep sections are usually the last to go, especially in wet ground.

There are several causes of rot when timber is above ground, but
pretty well the only one below is fungal attack, and fungi need air
to decompose lignin. Oak or elm will last nearly forever if either
dry or sodden, and even pulpy woods like poplar and willow will
last a surprising time. Damp and aerated is the problem.

By far the longest lasting native timber AT ground level is yew,
and it is the only one where its sapwood will last more than a year
or so at ground level, untreated - and even that doesn't last long
at ground level. Oak heartwood is OK, as you say, but its sapwood
rots fairly fast at ground level.


Regards,
Nick Maclaren.