Sorry that didnt' go well, but kudos to you for trying to help your plant. "this past spring, and all the leaves started going quite wilty. As I've started learning more about plants, I thought I'd investigate. As it turns out, it was VERY rootbound -- as in the roots had broken through the plastic pot and roots have completely enveloped the plastic. " I would assume it was getting/staying too dry at this point, with very little soil in the pot to get/be moist. It could have been near death already at this point if wilting a lot. You didn't remove the old pot before putting your plant into a bigger one? That's a huge no-no, but not chiding you for taking bad advice, it happens and is beyond your control. Not writing a paragraph about it to dwell on it, just to make sure we understand what's going on, and ask you to please not do that anymore. If roots that were almost always dry, from being outside of the pot, have lately been surrounded by moist soil, that could be a problem. Does that sound applicable? The more lively roots inside the original, smaller pot, are probably those which could most easily branch out into new soil in a bigger pot, but not with the walls of the old pot in the way of that. If you start snipping brown parts off, a little at a time, and don't get to a point where there's green inside, it's dead. Hope that's not the case! As sad as it may be, are you able to add a pic of your distressed plant? If needed, you can at least get plenty of sympathy.

I entirely agree with the spirit of what bboy said. It is best left alone and appreciating its natural habit. However, it's a danged shame to be removing this year's blossoms since they developed last year and the trimming will impact the show. That being said it is likely to do it no physical damage, even if done at this time. I venture to put that forth, as I've done it and quite severely I'm embarrassed to say. I planted one quite inappropriately through my own negligence, thinking it was a totally different cultivar who would remain quite dwarf and have a much smaller spread. The only options were to remove it, or pollard it. I figured if I tried to move it that it would not thrive, and I'd likely end up just removing it, so I decided to pollard it having nothing much to lose. I sacrifice the blooms every few years in the process, and it's a rather formal and unnaturally shaped tree now, but handsome enough I'm willing to invest in the high upkeep involved and it's been there now quite a few years. Your call.

Cherries prefer neutral soil, but it should survive acidic conditions reasonably well, as long as you don't make it too acidic. Resin PS spellcheck: 'Kanzan' (the 'w' is an all-too-common nurseryman's error)

Sure they'd fit & help keep the soil moist. Margaret from A Way to Garden has great suggestions & you already have some of the plants she has used around a tree. "The late-spring-to-fall palette under my oldest magnolia, top photo and above, is glossy European ginger, yellow Hakonechola macra 'All Gold,' Japanese painted ferns and Hosta 'June,' with a couple of young 'Lime Rickey' heucheras picking up the gold grass." http://awaytogarden.com/10-thoughts-on-successful-underplanting Here is a link that might be useful: 54 Favorites for Shade