leaf tip curl (and leaf death) in Japanese maple
We have a bloodgood in a container, planted about a year ago. The pot is approximately 18" in diameter, 30" deep. Last summer the tips of the leaves started curling and browning, until eventually the entire leaf would curl up like a dried hand - then fall off. Eventually the entire tree lost its leaves about a good month before established trees in the ground did.
The only thing that was suggested to me was maybe a fungus, so over the winter I treated the tree and the soil both with a sulphur-based fungicide, about once a month. This spring the tree leafed out beautifully (very thankful for that) - however in the last couple weeks I'm again seeing some browning and curling on some leaf tips. (And in the meantime I had been continuing the monthly fungicide treatment; though if it's a fungus in the roots or stems, the foliar and soil treatments might not work.)
Thoughts? It's well watered; in fact last summer one concern was that maybe I wasn't watering it enough (I know maples like water), but this summer I've been more generous, but am still having the problem. Could it be a deficiency of some kind?
Also, the tree gets full morning sun, up through about 1:00 or 1:30 p.m., then it's in full shade. Maybe that's too much sun?
Thanks for any input.