Tree Sap

We've got a few flowering cherry in our new (to us) gardren, they are dripping sap, quite a lot of sap from their trunks. They are pretty choked up with ivy, which we've left because the birds are nesting.

Is this normal or is it the ivy damaging the tree?

Gum oozing from cherry / plum trees can be due to a variety of causes, including  infected wounds, infections (fungal, viral, bacterial),  insect infestations (borers), or cold-damaged bark. It is most likely to be bacterial canker. If so, you should prune from the end of June to August to remove infected stems to health growth below.

The ivy won't have cause the oozing directly, but it is not a good idea to leave it there as it will reduce air circulation, restrict sunlight, etc.. 

Thanks again Gold1 Locks your a star!