Hello all, About a month ago we cut a dead branch off our Japanese Maple. Looking at the exposed branch there are now some black spots (won't rub off) on the cut surface. Is this anything to worry about? What is it? Recommendations are appreciated!!!!
@John F. First of all welcome to the maple forum. I agree with Osoyoung, not to worry. IMO It maybe pollution.
I know some studies have shown that it's not recommended to apply wound sealant on cut branches, and that is based on scientific studies on mature trees in the domain of forestry. But for bonsai, or potted trees, I'm a heretic : I always use Japanese wound sealant, a sort of plasticine-like product for bonsai. The price of it prohibits the use of it for big cuts anyway. So what I do on larger cuts is apply Bordeaux mix to prevent the rot entering deeper into the trunk. I'm pretty sure that if you use some copper-based spray, or mix, these black spots will not evolve, and maybe will disappear because they're probably some kind of moss, lichen, or mold that grows on decaying wood. The cut is already full of cracks into which rain can stay and make matters worse. At least that's what I concluded from about 20 years growing potted maples and deciduous bonsai, and trying both approches. Some can disagree : I know I'm at odds with scientists, which is something rather unusual for me, so take my comment for what it's worth...
