On Sat, 06 Sep 2003 01:58:26 GMT, animaux
wrote:

On Fri, 05 Sep 2003 21:55:26 GMT, (Terry Horton) opined:


I was curious about this a couple of weeks ago: summer or winter?
Surely, I thought, one should be preferable. Came across an article by
the McLennan county agent where he reasons that the ideal time to
prune live oaks is late winter.

Yes, the ideal time is in late winter when no possibility of virus vector is
alive and spreading oak wilt on the open wounds. August is another time you can
be sure there are no signs of this insect, either.

First, since August is becoming more and more a time of high drought
stress for trees, and since pruning is itself a stressful event, doing
so in August adds additional stress at just the wrong time. Also,
since live oak may drop some leaves after in response to pruning
stress, late winter allows it to coincide most closely with the
natural spring leaf fall for live oak.

Anyway, reading this thread led me to recall that interesting article.
Passing it on fwiw... :-)

What evidence have you read which says pruning causes stress to a tree which is
in dormancy in summer? Most of the plants go into a dormant period in high
summer, certainly trees are in that group.

Sun scald from lost foliage is always the biggest potential issue with
mid-summer pruning. Lateral buds forced by hormone levels thrown
askew would be another. And I suspect wound closure is far less
efficient under heat and water stress. Maybe one of the arborists
here can tell us more...

It has always been axiomatic that Texas summers are more stressful to
trees than our winters. With global warming and the blazing last
couple of decades, the difference is probably even greater (the nearby
Chihuahuan Desert and Trans-Pecos suggests our trees were already on
the climatic brink). One anecdotal tidbit... an arborist I know who's
been in the business for many years, says that his tree calls used to
be mainly disease related; now the overwhelming majority turn out to
be heat stress.

I am interested to learn, though, so
if you'd pass it along where you read that about pruning stress and trees I'd
appreciate it.

Very sorry, V, I've been unable to backtrack to the original story.
One of those items that seemed to make biological sense, that I
distilled and filed mentally for future use. So, like I said,
fwiw..:-)

One of the largest oak wilt centers in Travis county is right across
the creek from us (the creek probably saved our oaks from root graft
infections). Cutting down and grinding up live oaks is a dark, busy
industry over there. And our own wild oaks, like all unirrigated
central Texas trees, have really suffered from drought stress the last
few years. Each year they're showing more branches in need of pruning
than ever before. I just feel I have to get every advantage and take
every precaution I can for them, large or small.