Early spring, when its starting to push buds might be best. Late winter could still give you freezes that might damage roots that have been recently trimmed. I'm not sure about that particular species, but Acers in general (excepting Japanese Maples) can take pretty severe root pruning so don't worry too much. I wouldn't put it in TOO shallow a pot though as some of them like more water. I haven't done my research on A. pens... though so thats up to you. WF

I would think the best time would be after they fruited. At least that's when I repotted mine and pruned. Although, I've repotted(not pruned)in November once, because the soil that the plant came in was staying SO wet...I was afraid I would lose it to root rot. IF the mix its in now has a lot of peat...you might want to change the soil to something more porous. Are you letting your tree fruit this year...If you are letting it fruit, then the best time is after harvest. If not you might be able to do it now since you live in Miami and your winter is pretty mild...but if we have another winter like we had last year, you will have to bring it inside the house when the nights get below 32 degrees. But to be on the safe side and get the best results I would wait till the weather is consistently warm to do any drastic pruning...for you April might be the best time. Just my opinion.

Hello and welcome from a state close to me.. I would hold off on repotting until at least near Father's Day...This way you tree will be actively growing for a bit and much more able to handle the stress that comes with a full repot into a better mix, best if you rid the old soil using a Porous one that consists of mostly pine bark.... A soilless mix...Especially if you want to repot into a much bigger pot and have it last for a while. Remember how weak and tired our trees are after a period of long short days held captive indoors.. Any further stress would likely kill them. Upotting to a different size pot without root disturbance is an entirely different story. Those that grow plants under artificial light for hours to compensate for our lack of sunny long days can probably get away with repotting when they would like at any time of the year if their trees are kept very active all winter... Good luck and let us know if you need anymore help:-) Mike This post was edited by meyermike_1micha on Wed, Jan 15, 14 at 17:46

While you will hear dire warnings about transplanting in Winter, it really depends on your particular growing conditions. While most all of my tropicals and subtropicals go outside for the growing season, my cacti sit in an unobstructed, southern exposure where they get direct sun in the Winter but hardy any in the Summer due to the high sun angle. I have not had problems with Winter transplanting. I do not use a "gritty mix" per se but do use soils with coarse sand and incorporated perlite. I might water once a month in Midwinter (about the same for the Summer due to fact that they are more shaded in Summer). Personally, I might loosen up the root ball some, but not remove all the old soil as this seems likely to shock the plant. The only reason for removing most of the old soil would be if it were being planted into dramatically different soil type (such as a gritty mix).