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My trident maple bonsai went into dormancy entering winter. I repotted It, carefully removing some large roots and pruning for radial roots.

Bonsai soil mix of peat, leca, stone, bark. Extremely well draining. The pot is currently taking 4 days to dry out. Temperatures are 18-21 Celsius and not much wind. Its outside under a shade cloth area. I would say it's a little darker than it should be.

I pruned a few branches back.

After a few weeks, as I saw some life emerge, I fertilized with 5 3 1 and treated it with systemic as there were signs of aphids on my willows a few feet away.

Spring arrived and it pushed out leaves very quickly. However I have 30% of the leaves are curled and not flat and open. They have dark spots in the recesses of the leaves. Have I overwatered, fertilized or is there a known condition I could try treat? Also should I remove these leaves or leave them on the tree?

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There can be different reasons for leaves to curl, to name a few: light, temperature, too much water, too much fertilizer, pests. If I understand correct it happened after you trimmed and re-potted the bonsai tree. Is there a good drainage of the water from your soil? This kind of leaf damage reminds my of too wet soil. You should water the pot every day, but the water should be able to get thru the soil and leave via the drainage holes. (Edit: drainage and soil sounds to be okay!).

Temperature seems also fine to me, it is not too hot.

One other reason I can think of, is that the roots were trimmed too much, and are not sufficient for the above ground plant (too small to provide water and nutrients for the whole plant). The root mass will have to regrow before this problem is solved.

  • the tree seems otherwise very healthy. If I did too much root pruning, I would have noticed it struggling a bit? there are many leaves healthy as well as quite large – JonathanC Oct 26 '17 at 11:30
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I think it may be fungal and possibly because of water hanging on the leaves. I have several bonsai (but not a trident) that exhibit this problem from time to time. I try to avoid watering the foliage but am not always successful. Spraying with a solution of 2 tablespoons of 3% hydrogen peroxide (from the grocery/pharmacy) in a quart of water after I water the trees arrests the problem I have with certain of mine. You may want to give it a try if your problem persists.

  • I have sprayed it a number of times, when temperatures increased. thank for tip – JonathanC Oct 26 '17 at 11:31
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If you unroll the rolled up portion of the leaf and find no insect evidence, I agree it is likely fungal. As I am just a forester and not an arborist, I can't advise on treatment very well, except for applying copper spray. If you take care to research the effects of copper, and can strictly follow instructions, it's worth a try. But I mean strictly.

  • There are no insects at all. I had a similar effect on a ficus, but that was definitely insect related, and I see nothing on the maple. I will look into copper spray, not used it before. – JonathanC Oct 26 '17 at 11:32

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