Answer: Japanese maples are relatively slow growing and are perfect for large containers. I have one planted in a half-whiskey barrel and it's been happy for nearly 20 years. So, something of that size will be fine whether it is wood or concrete. I'd stay away from plastic because the tree will live longer than the plastic will hold up. Whichever container you choose, make sure that it has plenty of drainage holes on the bottom and fill it with half topsoil and half potting soil for weight (you don't want your tree to be topheavy and topple over), and for good drainage.
Best wishes with your lovely Japanese maple!
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