Restricting growth........

Is it common to yearly prune a tree to stop it getting too big?

For example, a want a tree which which potentially could grow to 10 meters (too big for the garden),  but i dont want to grow more than 4 meters.

Could there be long term damaging effectsto the tree or is this normal?

Confused-have you bought a tree or want to buy a tree or do you have a tree in the garden already

And why would you want a tree that could grow to 10 metres but you only want it to grow to 4 metres?

It may just depend on the variety-why not just buy a tree that only grows to 4 metres

Sorry for being vague, im looking at getting a particular acer for the garden (osakazuki), but it could potentially get too big for my garden. There are other types of acer which dont get so big, but i really want this one.

No, it's not normal or ideal - for a start, pruning will encourage more growth. However, the tree you mention doesn't grow that fast, and it is possible to prune it gently every year to keep it in bounds. It's best to start doing this before the tree becomes too big, however, as pruning then will leave ugly stumps.

Acers grow slowly. You can certainly prune it to prevent it getting too tall.10 metres is its maximal possible height, I would say 6-8 foot is the height you want to keep it at and taking out the leader will give it more shape.

Acer osakazuki only grows to 6 metres, it's not a very big tree and it doesn't grow very fast. It has fantastic autumn colour, but it needs a sheltered spot.

Bagz wrote (see)

'taking out the leader' ? Would this be the main vertical branch growing up through the centre?

Yes, if you see a few buds then cut above those to be the main horizontal branches. That should give you a nice shape. Also put the cut off leader and place in some compost, it may root.

Busy-Lizzie wrote (see)

Acer osakazuki only grows to 6 metres, it's not a very big tree and it doesn't grow very fast. It has fantastic autumn colour, but it needs a sheltered spot.

I have seen them 10 metres by about the same in DC, in a sheltered street but in almost full sun - no idea on how old it was.

If this is potted, or could be, then a root restricting bag might be an answer?  I don't know if you can use them in the ground, I imagine the roots would just escape and you'd have a big tree anyway.  Why not get a tree suitable for the site?  If you must have it and don't already, then a good clay pot and the aforementioned root restriction bag might do the trick.

I've actually gone and bought 2 now, an osakszuki and a orange dream (3 meter max).  Going to keep both in pots for now and learn about keeping them in good shape etc and see how things go.  Taking on board everyone advice, we'll see how it goes, they may never make the ground and stay in pots.