Alasdair

If you prune maples with a rather blunt tool it stimulates the release of distress hormones and they don't 'bleed' as much. Using a sharp impliment does less damage, but the tree doesn't notice so does nothing to speed up the healing process.

I have tried this experimentally on a maple of kine, removing two shoots. One with a surgical scalple and the other with my thumb-nail. The scalpled shoot ended up dripping white sap,where the pinched shoot just formed a blob of sap.

Anthony,
When you remove the branch, try and crush the tissue around the wound to reduce the sap loss by using a blunter tool than normal if you are worried.. But i would agree that bleeding is hardly harmful All that happens is the tree looses some of its sugars.

Look at sugar maples, they are drained of sap o make maple syrup, but keep on growing...

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I can feel another "I wish that was my tree" moment coming on...
Currently studying BSc Plant Biology at the Universty of Wales, Aberystwyth