time already to rootprune and repot?

underside of leaves, white specks

I can't really tell, but those white specks look like some kind of egg. Aphids?

I don't know where you live, but here in MD we're already in the 90s. I have about 9, 6-10 year old trees that need to be repotted badly, but with this heat, I'm afraid it will just plain kill 'em. I'm going to take my chances in the fall, even though in the past my larger trees have had such horrible, knotted & grown together roots, they were impossible to cut out. Horrible.

That said, before the heat, I repotted well over 30 (might be over 40) maples, plus hosta and heuchera I'd planted in their pots with them (do NOT do that) and this year, they've all survived. Last year in the spring? I didn't have such good luck.

All that said, I'd wait.

Too late in season to repot now. Unless you are very experienced with these trees, I would recommend you only consider repotting when the tree is fully dormant. And if you are potting up to a larger sized container, there is no need to root prune either. Root pruning is only done periodically to confine the root system to a specific container size. Like bonsai, it will also limit the overall size of the tree as well.

I agree the specks do look a lot like insect eggs, probably aphids which seem to be attracted to new growth on JM's. Suggest you just hose them off with a stream of water - Japanese maples are extremely sensitive to insecticides applied to their foliage.

Thanks ladies! I will take that advice and keep it how it is til it's dormant. And I tried to gently rub/scrape the specks off the underside of the leaves but they don't want to budge. I will spray them w water today anyway and hope for the best. The tree seems healthy otherwise, as far as I can tell. None of the leaves is curling or drying or anything.

Don't worry about those spots on the underneath side of the leave. All my green leave maples have them, and they are perfectly healthy

Thanks mapleman! I gave them that one rinse initially but have since forgotten all about the spots. The tree is fine and it's been months : )