AusBonsai

Hi everyone,

over the last couple of weeks I've noticed a dark brown mark on the trunk of one of my Japanese maples. It seems to be spreading up from the soil. I pulled the root ball up to take a look but there weren't any obvious signs of rot. In fact, the roots looked very healthy. The foliage looks ok. generally a bit burnt but it's a variegated variety that's been getting a lot of sun this year so that's nothing out of the ordinary. Any help is appreciated hopefully it's curable

Looks a bit like sunburn to me, in which case that part of the trunk will die off in my experience.
I had a similar thing happen on an olive, which isn't the end of the world because you can carve etc to hide/disguise iton those. Probably a bit more problematic on a maple however.
Has it changed environments, you say it has had a lot of sun exposure?

There is an infection that turns bark black and spreads from soil up the trunk but I've only ever seen it at the very start of spring and usually when the soil is cold and too wet.
I agree that this is far more likely to be sunburn. That's also something that happens to maples this time of year. I've had parts of trunks killed after defoliating or pruning when the trunk is exposed to hot sun suddenly.
Is the mark on the sunny side of the trunk or has it been moved to a hotter location, etc?

Plus 1 more for sunburn; I planted a shishi garden tree out and it’s suffered trunk sunburn this summer with a large black section now in the trunk.

Not the end of the world, either air layer to remove it or let it die back and become deadwood. At that size I say air layer above it to remove it sometime in the future

Thanks for your replies! This side doesn’t generally face the sun but this tree is just in a plastic growing pot and is prone to blowing over so it’s quite possible it was on its side for a while one day and received too much sun. At any rate, I’m glad that it’s not necessarily a death sentence for this tree. I’ll keep an eye on it and maybe consider air layering next year