Japanese Maple leaf burn
I have a Full Moonrise Japanese Maple that is about 4 ft in height and was planted in a container at the beginning of June. It was growing well and structurally is still very sound. However, for some reason all the leaves have started showing burning around the ends & edges of all the leaves. They are turning brown and crispy, but the odd thing is that the browning & leaf burn is not spreading to the rest of the leaf, nor are the leaves dying or falling off. It seems to be limited to just the edges of all the leaves, and even brand new leaf growth is showing brown edges almost immediately within a day or two of sprouting. I'm confused about what the issue is, and because of how uniform the issue is effecting every leaf so similarly, I am wondering if it's not some type of disease / fungus or pest related issue that is causing the problem? I've moved the plant to avoid excess sun, and cut down on wind, but it has not helped and new leaves are showing the same issues with burnt edges. I've tried treatment with a fungicide, and then neem oil as directed, and no improvement in the plant... I'm at a loss, and it doesn't seem to be killing off the tree, but it has definitely slowed down the growth of the tree. Any suggestions or help would be extremely appreciated! Thank you!
Certified GKH Gardening Expert
Without seeing the issue, I am limited to educated guesses, but I will do my best to help.
This sounds like nutrient burn. It could be multiple nutrients, but usually nitrogen. This can happen when planting into very rich soils, or adding amendments that are too strong for the tree.
However, I cannot rule out fungal infection, since I can't see the damage. Uniformity is strange for an infection, but sometimes they start uniformly and move towards random patterning, or even the other way around!
For now, I would recommend flushing the soil with quite a bit of water, as long as it has plenty of drainage to let all of that extra water out immediately.
If this does not have drain holes, then I would recommend. carefully, pulling out the tree and replacing all soil with a less nutrient rich blend.
Here is an article that will help you to grow these trees in container: https://www.gardeningknowhow.com/ornamental/trees/japanese-maple/japanese-maples-in-containers.htm