Posted: 08/11/2014 at 14:26
Hi Helen, potted trees can be planted at any time of the year but now is a particularly good time. Add some fish, blood and bone fertilizer to the planting hole and soil removed from that and mix it in a bit before planting the tree. It might be worth sprinkling some mycorrhizal fungi (ie Rootgrow) onto the root-ball before planting it into the hole.
Just one thing though: Acers like neutral to acid soil, so if your soil is alkaline (eg if you live in a chalk or limestone area) I would recommend that you just transplant it into a larger pot instead of into the soil where it might suffer.