Growing acers (also known as Japanese maples) in a pot or container? Take a look at this speedy Quick Tips video, as Lucy Hall, BBC Gardeners' World Magazine, reveals the best time to repot them. She also gives her top tips on how to repot it, including which compost mix to use and pot size to go for.
Spring is the time to repot your acer, when it begins to sprout new shoots. This disturbs the roots while there is little foliage on the tree. The new compost will soon be filled with new feeding roots. Use a compost of three parts John Innes No.2 with one part soilless multi-purpose compost and one part extra grit, to aid drainage.
Choose a pot slightly larger than the old one, so you can fit the flat of your hand between the rootball and the side of the pot. Situate the pot out of full sun, and water regularly.