At 12:29 PM 1/7/04 -0600, Tim Ahlen wrote:
I started a thread on the gallery awhile ago that reflected my frustration
as well as my tenacity at trying to keep JBP bonsais alive in the Dallas, TX
area (Zone 8b). Several tried to encourage me to keep trying. Ernie Kuo,
based on his knowledge of the area and the experience of other Dallas
enthusiasts with JBP, encouraged me to try other species. That kind of
encouragement should be (and is!) taken very seriously.
Still, I look around the landscape in Dallas and I see JBP's thriving in
Dallas' heavy, alkaline black clay soil and everything else that goes along
with the environment here. Could one of the primary factors that lead
enthusiasts in tropical or other warm climates to despair over JBP's be that
summer temperatures cook the roots in unshaded/unprotected pots?
For the last two years I have buried two black pines in the ground in their
growing pots during the spring and summer. One of them is an older tree,
about 3 inches in diameter; the other is one purchased in a 1 gallon nursery
container and is about 1 inch in diameter. The holes were no wider than the
containers, but dug deep enough that I could put gravel in the bottom to
insure drainage. It seems that these two trees are my healthiest pines. In
fact they are the ones I've had the longest.
The most common result I have with JBP's is that they get a kind of worm
infestation in the new shoots in July and August and die-- from pine tip
moths or borers or something. Because there are healthy trees around,
planted in the ground or buried like the two mentioned above, I'm guessing
that my dead trees succumbed because of stress. Am I on the right track?
Tim
Yes, I think you are on the right track. There is an article at my website
by Andy Walsh that goes into the dangers of excessive soil temperatures:
http://www.evergreengardenworks.com/rootheat.htm
I know for a fact that it is a serious problem in growing White pine, Pinus
parviflora, in containers. My losses went down to almost zero once I began
putting them under shadecloth in the summer. Although the ambient air
temperature is the same, the pots don't heat up above this point under the
shadecloth. Black nursery pots, and even stone bonsai pots, are little
solar collectors in direct sunlight.
I have observed the phenomenon of dead roots on the sun side of the pot,
while the shaded side roots were fat, white, and healthy. It isn't as hot
here as there, but it is still a problem for Pinus thunbergii that I plan
to address. Your solution of plunging the pots is a good one, but is
impractical for me. I plan to paint the pots white on the south and west
sides. There is a shade paint compound made for greenhouse plastic film
that can be sprayed on, but it doesn't contain a binder so it comes off
with repeated applications of water. Since my plants are drip irrigated, it
should last through the summer.
Brent in Northern California
Evergreen Gardenworks USDA Zone 8 Sunset Zone 14
http://www.EvergreenGardenworks.com
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