Why does this hornbeam have these bumps? Goats have prepared this tree over decades. They eat new growth. Like when you cut a hedge constantly it reacts with lots of new growth. The hornbeam has the habit to throw new growth from the base besides on the top. So the goats could not get into the crown at one point anymore. But they could get underneath go eat the new growth at the base. And so over decades the bumps appeared.
If one thinks that they are ugly you better get another tree, I am afraid. One could cut them off one by one and have a fat trunk with a hundred or so ugly scars which will never disappear.
It would be better to do nothing and just feed and water the tree well. It will grow on the top and over many years due to the lack of goats in my garden the trunk may become more handsome.
Or does it have to? Twenty five years ago I made this photograph of a European (English) oak in the south of England. It has this most unusual sexy trunk. I wanted to see what it would look like in a bonsai pot. I can see amazing similarities to my hornbeam. If someone ever doubted that one can jut go to nature and copy a few details of a real tree and create a naturalistic bonsai - here we are.