By Babyhare
United Kingdom 
I have inherited a mature weeping silver birch. It needed some lower branches removed as it was laying across the greenhouse roof. I removed them and now it seems to be living up to it's name and weeping sap. Have I done something wrong and killed it? The cuts were not done at the main trunk, but further out into the weeping branch formation.
22 Mar, 2011
Answers
I would prune in winter when they are dormant, as with other deciduous trees. In spring the sap is actively rising so it will bleed copiously. Don't worry, it's highly unlikely that you've killed it - but it will appreciate a feed to help it recover.
22 Mar, 2011
I also would cut it back to side branches at least 1/3 as large as the branch you cut. I remember that the white birches in Flagstaff, AZ were really good at making "brooms" when stubbed back!
22 Mar, 2011
The best time to prune Birch is late summer/early autumn - the sap is already receding, and it gives the tree time to form a callus over the cuts before winter gets a grip, and before the sap rises again next Spring (taken from RHS and Readers Digest Encyclopaedia).
23 Mar, 2011
Pruning of these trees should be done in summer for just this reason - they bleed like crazy if you do it any other time. Nothing much you can do about it now, should eventually stop.
22 Mar, 2011