I suspect you may be watering too regularly, and the roots are waterlogged...can you check them?

As AmbleA says possibly overwatering...

Just looked it up and this Acer (shaina) seems a little difficult to grow - it hates to be over watered (check drainage in the pot), does better in a pot, is hardy, but prefers a fair bit of sun compared to most Acers. Hope that helps

Can't check the roots unfortunately but I would have thought it would turn yellow rather than white if overwatered?? When I made up the pot, I put in half a ton of stones at the bottom so I doubt that the drainage is bad. I will keep an eye on it and see. Thanks for all the suggestions though - I will persevere...

I hope there's a hole in the bottom of the pot - if not, that could be the cause. Turn it out of the pot and check

Don't worry bamboo - I actually did check and there is definitely a large hole in the bottom! Although I'm no expert I have learned that pots should have drainage having killed off a beautiful rose last year by not putting holes in the pot. I wonder if the spray I used for the black flies would cause the white tip problem?

Oh, white tips, from the first description I thought they were brown and withered. White discoloration is usually associated with wide temperature fluctuation - maybe the thing put out its leaves and then got cold. I'd be inclined to move it to a sunnier spot, see if that helps, since it seems to prefer a warmer situation.

OK, will do, but when it was in a warmer spot then the other leaves seem to get fried - seriously - I don't think you can win with this one! Thanks for all the advice.

Realistically the fussier Japanese acer's survive better planted in the ground - nice cool roots, easier to shelter. I often wonder why we are so bloody minded as to try to grow plants in out gardens that nature would not put there? Is it a bit like a woman who has curly hair and wants it to be straight? Whilst her sister with straight hair want curly hair....

I am that woman - long curly hair which I have straightened regularly! Perhaps that's why I subconciously chose this plant?! I think its more to do with the fact that I thought it was beautiful and I wanted it in my garden so I could see it all the time cos I'm greedy like that! Food for thought though MG.

Don't worry Muddywellies - I am just as bad! My hair is naturally wavy do I let it? Do I flip!