I have a similar problem.

Your Acer needs partial shade - it sounds like you have it in strong sun (early morning till afternoon). These plants grow in the wild under the tree canopy so grow best in part shade.

One of my Acers', a Palmatum 'Butterfly', has very few leaves and looks sickly. I have been watching it for a few weeks now and took action yesterday as the buds have not produced leaves yet whilst its twin has. I took it out its pot and found it was very dry and pot bound (even though I repotted in Autumn and have been keeping it watered). It is now in a larger pot with fresh soil and feed. Perhaps you can check that your Acer is not too dry and shift it to shady spot?

Make sure you have it planted in ericaceous compost and be prepared to feed/mulch as it wont get the same level of nourishment it would if planted in the ground.

Hi. Thanks for the responses.

Kildermorie. By part shade, do you mean dappled shade? If so, I have nowhere suitable. The garden's on a bungalow estate where there are no large trees and the garden itself has no trees at all. I have a choice between morning sun, afternoon sun or full shade. Which do you think would be preferable?

I think it could probably do with a bigger pot. I have a nice big one available that I'll move it to.

Moon Grow. I didn't realise they needed ericaceous compost. Thanks for the heads up on that. I'll get some tomorrow ready for repotting :)

Acer negundo isn't as fussy as A. palmatum as far as shade and compost are concerned, but it will definitely need regular feeding, especially with the extra water needed to maintain it in full sun. What did it look like while in the shade, Dioritt, and if pretty, how did it get to the state it's in now? Did branches die?

Go for afternoon sun rather than morning sun and use any small bit of shade to help to screen it... If you can lift the container you might want to move it into full shade for part of each day.

It's in Mum's garden and she wouldn't be able to lift it to keep moving it about. I'll move it to afternoon sun though and see how it goes.

It looked very unhappy in full shade but it wasn't being fed or anything there because the garden was neglected. I repotted it and moved it to Mum's garden (my own garden is still very much a work in progress so all the plants in pots were moved over to Mum's). It still looked as miserable last year, though, even though it was given regular feeds. I suppose I ought to feed it with ericaceous feed instead?

Tugbrethil's right - this tree isn't a delicate Acer like one of the palmatum varieties, and is fine in full sun - what it won't like too much is lots of wind. It's also a rather large tree if left to its own devices, and won't do too well for too long in a pot, should be in the ground. Suggest you ignore it for this year, and in winter when its dormant, cut it right back - Acers should be pruned in winter before the sap rises, although pruning back a bit in early autumn is usually okay. This particular Acer also has no specific requirement for acid soil.