By Martylew
United Kingdom 
I have a purple acer that has been happily growing in a terracotta pot for approx the past 3 yrs. Now the tree/shrub is, I feel, outgrowing the pot. I feel I may have 2 options; firstly to buy a larger pot and secondly to plant out. If I do the latter, can anybody kindly advise approx how large, by width and height, its likely to grow to. I'm guessing re-potting acts as a growth restriction, whereas, planting out, does not. Thanks to anybody who can advise.
11 May, 2019
Answers
I wonder if yours is Acer Bloodgood, in which case it can grow to at least 4feet high and wide.
11 May, 2019
Sheilabub did you mean 4m high.
12 May, 2019
No Scotsgran! But I guess my old one might have been 5ft x 5ft ... I’m not very good at guessing :)
12 May, 2019
Sheilabub I googled A.'Bloodgood' because I fancied one but the RHS advice is very confusing. They say the ultimate height and spread can be 2.5m to 4m. The time to reach the ultimate size can be in 10 to 20 years. That would be too big for my garden. That was my reason for asking you if you did mean 4m. https://www.rhs.org.uk/plants/details?plantid=27
12 May, 2019
If only I could be precise regarding the variety of acer. Sorry, but it was supermarket bought on a bit of a whim as it looked so lovely. That'll teach me to pay more visits to a reputable garden centre. Think, maybe I'll re-pot it as planting out could lead to the tree/shrub growing rather higher and wider than my garden can cope with. Thanks to you for your comments.
13 May, 2019
Martylew I planted out an attractive supermarket bought acer when it needed repotting. One of the members opens her garden with the Yellow book scheme. She grows lots of different acers and keeps them trimmed to the size of the space she wants them to occupy. Her garden was on TV. Sorry I do not recall her name but another member might. I now keep my one trimmed and it is not suffering from me doing that. Good luck with your one.
13 May, 2019
Its not possible to say the ultimate size without knowing which variety of Acer you have - do you know the varietal name? It sounds like an Acer palmatum variety of some sort, but even those differ in eventual size...
11 May, 2019