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Wanna-B/onsai
Join Date: Aug-2007
Location: Calgary
Country: Canada
Posts: 44
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Curling Palmatum leaves...Why?
Hello people that know more than me,
I'm pretty new to bonsai and newer still to Japanese Maple bonsai. I live in Zone 3b (Calgary, AB, Canada) -- it's cold and windy and we experience temperature inversions regularly.
Calgary: where Japanese Maples go to die.
What I have is what I estimate to be a five-year-old palmatum pre-bonsai. When I purchased the tree it was already looking a little less than great. I asked the owner what his thoughts were on the curled and crispy appearance of some of the leaves. He advised me that the tree had been under heavy shade cover for a number of weeks and probably needed some light. I found this answer somewhat suspect considering what I've read of palmatum’s preference for dappled shade and the fact that it was rather (to my eyes anyway) bright in the greenhouse. Nevertheless, I took its somewhat weakened appearance as an opportunity to negotiate a fairer price and I left tree in hand altogether pleased, optimistic that I could rehab it well enough until dormancy.
Well...that hasn't worked out quite as well as I hoped.
The tree hasn't declined particularly: some of the young shoots are gaining strength and the tree has a sufficient supply of healthy, well shaped (albeit large) leaves -- but it's not thriving. In addition to the growth there has been a slow, steady development of misshapen leaves that brown along the edge, curl upwards, and curl laterally to the left and right. I've checked out the roots and included some pictures below; they (the roots) don't look great, but not all that poor either. Though it may be hard to tell from these lousy cell-phone pictures -- my camera's busted -- I'd appreciate a second opinion.
Because I obtained this tree late in the season I haven't attempted repotting it into my usual mix of river sand, turkey grit, horticultural charcoal, decomposed fir bark and fluorite. The previous caretaker told me he had successfully overwintered the tree in it's present mix but that it took a very long time to push buds (mid-June. Which is late, even for Calgary). The soil is very dark. I think it's mostly decomposed bark and perhaps, leaf mold (?) that has broken down a lot; I saw a few bits of peat on the surface that I removed -- smells wet and loamy. The soil texture is quite firm but spongy enough that it appears to drain ok -- really doesn't look far off from what Peter Adams recommends (more grit would be nice). I figured it wasn't worth risking a repot especially if it had already made it through one winter.
Care that I've provided:
Since I was advised that the tree was light deprived, and the weather was already starting to get pretty cold (we had already had several considerable frosts) I decided to keep the tree indoors four feet from a screened window under a 60 watt blue halogen. Calgary gets WINDY like you wouldn't believe and the idea was to gently acclimate the tree to the cooler weather by letting the cool air drift in waft over the leaves. I kept a very close eye on it to make sure that the leaves weren't desiccating. On average it drops between 0-3 C (33-37.5F) at night but soil temperature tends to stay about 8-9 C warmer (48-54F). My guess is it needs to get colder before I'll see anything in terms of colour change and leaf drop (and it will, to be sure).
I water the tree when the surface is just beyond being damp to the touch (if you dig in with your finger it's still slightly damp). I tried the chop-stick method which I've got down to a science with my Chinese elm and Euonymus, but I was worried that I couldn't estimate the dampness of the stick quite right with the maple. I water with tap water that I sit out for 24 hours and then amend with aquarium conditioner to down the pH (the majority of Calgary's water is from a limestone reservoir - average pH is 8.2). I water by the method Gustafson suggests: once misted to break surface tension, then again to saturate 10-15 minutes later with a light upward facing rose, and finally a cleansing rinse 15-20 minutes after that.
I have not fed this tree since I obtained it in early September.
The former owner fed it bi-monthly with "Chrysal Liquid Bonsai Food (4-6-6, with trace elements)"
At any rate, the tree began to show signs of improved vigor, but also persistent issues with the leaf shape that seem to be getting worse.
Potential culprits:
I found a caterpillar and a spider beneath one of the leaves. I named them Herman and Judith because I believe it’s immoral to dissociate myself from corporal punishment. Some of the damage is definitely caterpillar-related, but the curling I don't understand. I applied a light spray of Neem oil mixed with water and dish soap to take care of any other potential pests a few days ago.
RIP Herman, Judith and your kin.
The nursery I got the palmatum from had a bad infestation of spider mites in early August. I didn't see any spider mites on my tree or evidence thereof (and I checked in on this tree over several months before I bought it), but I wonder if a haphazard pesticide applicator may have damaged the leaves? I know 2-4D can do a number on leaves but I can't imagine what purpose they would have for spraying herbicide in their tropical section. Any idea if there is a pesticide used for mites that might be responsible for this sort of damage?
I'm tapped...Please help me.
How do I make this better?
Love and respect for anyone with the patience to meander through my parentheses.
Sincerely,
J.D. Wolfe
P.S. also attached are some blurry pictures of the leaves to give you an idea of the damage.
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