Acer lower branches

Can anyone advise when, how and what to do to 3 acers, 3 years in the garden to stimulate LOWER BRANCHES to grow from the bare trunk? I want to increase privacy through screening.

Thanks.

 

If there are no visible buds then you're unlikely to get any lower growth. Trees always grow up and outwards to search for light and tend to dismiss their lower branches when the are no longer needed. Cutting/pruning the crown of the tree may encourage adventitious buds beneath the bark to sprout, but these would probably, again, be up in the crown rather than lower down.

 

I saw something once on a programme with Chris Beardshaw-I am by no means advocating it but what is that thing where they cut a slice into the trunk that stops the sap rising up that particular "vein" ( can't think of the word) and forces new shoots below the cut.