at about 7:30 a.m. today, tuesday, 11/18/08, with nary a breeze in sight, one of 
the three main trunks of our ~100 year old coast live oak fell on the corner of 
our garage.

pix, some with labels as well as unlabeled pix:

http://tchester.org/temp/081118/


unfortunately, this message could be subtitled: "How NOT to take care of your 
oak tree".  (:-(  i'll probably put some of this info online after i get 
comments back from some of you.


the basic problem with this oak tree is that the builder of our house paved over 
three-fourths of the root system of this tree.  we bought the house several 
years after it had been built, so had no say in this terrible decision.  what an 
unkind thing to do to so old a tree!

so this tree has been on the unhealthy side ever since we bought the house, and 
perhaps i should have simply removed it before it fell.

however, i've seen a number of coast live oaks growing in challenging conditions 
in the wild, with lots of their roots exposed, and still surviving, so i had 
hoped ours would, too.

i now wish i had paid roger boddaert, our local fallbrook tree expert, to come 
over and review this tree to give us an expert opinion on what should be done 
with it.  but hindsight is always wisdom...


i had in fact been a bit worried about this tree in the last month or so, since 
it produced a HUGE crop of acorns this year, at least a factor of 3 (and maybe 
10) more than ever before.  i knew that plants often reproduce like mad when 
they are stressed to near death.

but i failed to act on my knowledge and have a knowledgeable tree person come 
and inspect the tree before it failed...  (:-(  i just supposed it was a banner 
acorn year for all oaks in fallbrook.

it looks like a crane will be needed to lift the trunk off my roof to safely 
remove it, and to prevent further roof damage.


what happened was that one of the three trunks split off at a crotch. (actually, 
the trunk that fell was probably originally a branch that grew very large.)

i'd always heard that crotches were a bad thing for trees, but i thought it was 
something to do with the physics of the way the trunks come together at the 
crotch, and the stress loads on the trunks as a result of the crotch. i learned 
from the tree guy, dave jones of tierra del verde arbor care, what the actual 
source of the problem was.

in at least this case, there were THREE other problems associated with the 
crotch.

first, and probably the worst problem, water collects in the crotch, penetrates 
the bark and causes fungal growth, aka "dry rot".  so the crotch led to wood 
decay.

second, the crotch "grows upward" as the trunks grow together more each year.  i 
knew that this often happens, and the bark eventually surrounds the merged 
trunks.  what i didn't know is that the individual trunks KEEP GROWING inside 
the crotch, which actively pushes apart the two trunks until one falls.  you can 
see the "bark line" in one of the crotches higher up the still-standing part of 
the tree in one of the pix linked above.

third, acorns and other plants actually germinated in the crotch, and grew root 
masses into it!  note the mass of small roots in one of the pix above, along 
with some much larger roots.


finally, i thought the tree had "termites", since there was a fine powder around 
the base of the tree, but that fine powder was due to an oak wood-boring beetle.  
that beetle apparently played no role at all in the failure, even though that 
fine powder was the main thing that worried me previously.  don't that beat all!


some of the pix above show the bark "inside" the crotch, the white fungus 
threads, the roots of other plants, borer holes, and, of course, the extensive 
dark dry rot.


wayne, jackie, roger, or anyone else, please let me know if any of this 
explanation is not correct, if you can tell from my pix or from your experience 
with such oak failures.


here is how both susan and tom experienced this.


susan:

We had a bit of excitement.  I'd just gotten home from dropping Matthew off at 
school and parked the car in the garage.  I stepped out on the driveway to pick 
up the morning papers.  I heard some little crackling noises, so I thought there 
was an animal up in the oak tree.  I stepped under the tree to look up and see 
what kind of animal. The little crackling noises became one enormous crack 
sound.  I ran faster than I would have thought I could still run.  I managed to 
outrun the falling tree branches and looked back to see the garage roof a bit 
crushed by the weight.

We've already had a tree expert out to look at it.  He says he'll need to rent a 
crane to come and lift the enormous weight off the roof.


tom:

i was asleep in bed when a "strong earthquake" raced through the bedroom. it was 
a big noise; the cat jumped off the bed and ran down the hall.

i was quite puzzled about this "earthquake", since if it was so strong, there 
should have been more shaking, and i should have felt both the P and S waves.

furthermore, it seemed consistent with another earthquake 10 miles north of 
palomar, since it appeared to me that the wave went from east to west across the 
bedroom.  (but remember, i was asleep until this event woke me up.)

all became clear about 20 minutes later when susan told me one branch of the 
tree had come down.  (;-)

during those 20 minutes, susan was out there examining the damage, with many 
neighbors, and very pleased she had escaped injury.  (:-)

the neighbors were asking susan why i wasn't out there examining the damage with 
her.  but i don't get out of bed just for a little earthquake.  (;-)

if the tree had fallen at an azimuth just 30 degrees different, it would have 
fallen on the roof of my bedroom.


i vote that we continue to build houses that can support not only the weight of 
the roof and walls, but have considerable margin built in for additional weight 
loads like this.  (:-)


-- 
tom chester