It's too late to repot w/o considerable (added) risk of losing the plant. You could pot-up w/o a problem, but just going by the odds, I'd say you have a (collapsed) soil issue, which is a problem that potting-up won't fix. ......................... The string of dots was me, thinking. ;o)

I have an idea, but first, pull the plant out of the pot & inspect the roots. Is the soil soggy at the bottom? How tight are the roots? Do they smell earthy - or sour/rotten near the bottom? Are they white/tan and succulent - or dark brown/black and soft/mushy, especially near the bottom?

Actually, I have 2 ideas. ;o)

Al

It's been raining here for the last 5 days and I think it'll be mushy anyhow. ;o) Stringy hairlike roots are coming out of the bottom of the pot and I'm worried to even lift it. What are your 2 ideas?

I agree it's not the ideal time to do so, but I've repotted containerized maples at various times, including in the middle of the growing season as the need arose, and it CAN be done successfully. I think the alternative - an obviously suffering rootbound tree surrounded by depleted soil - warrants attempting to correct the problem now before it becomes worse.

I'd be very interested to hear more from Al about his 2 ideas, but my suggestion would be to unpot the plant, gently wash all the soil from the root mass (or as much as you can get) and as carefully as possible untangle the roots as best you can. Prune away any dead roots and trim back (check out the thread this page on root pruning for specifics). Repot with an appropriate soil mix - 5 parts bark fines to 1 part peat and 1-2 parts perlite, pumice or turface (or see other discussion on maple potting soils). You might want to consider a slightly large container size as well. And I'd definitely include a controlled release fert (CRF) at the time of repotting.

Your tree is a weeping, redleafed dissectum, possibly 'Red Dragon' (Acer plamatum 'Red Dragon') but I'd prefer to see a close up of an entire healthy leaf before being certain. There are several other cultivars that appear very similar.

Here is a link that might be useful: root pruning containerized maples

I've repotted containerized maples throughout the year with few problems. Just try not to disturb the roots more than necessary. Use high quality potting soil.

Since the tree is already leafing out, it would probably be best to wait until the new growth has hardened off some, which would probably late May or early June.

Your tree could be any number of red dissectum varieties. A lot of them look very similar and are hard to distinguish until fully leafed out, and even then most people could not identify the variety.