We also have one that must be.....o....50ft or so. I don't believe it has ever been fed in it's life.
However if I was wanting to feed anything organically there are a couple of things I would consider doing.
1)Make a soup from the contents of your compost heap in a 3ltr juice container or bucket, find some Comfrey and rip the large leaves up and add them. Wait for a week or so, agitating the mix whenever you walk past and when it all looks nice and decayed....feed.
2) Blood and Bone mix. Should be readily available at garden centres or landscaping yards. Buy it by the bag or the bottle(in liquid form).
3) Mulch your trees.
Hope that sort of helps.
