Question: My pear tree has thorns, and the fruit aren’t any bigger than marbles. I thought I was getting a good variety. What is the problem?
Answer: The problem is that your good pear variety has died back to the rootstock. What you’re seeing is probably Callery pear. It’s a more rounded, open tree. The branches have thorns, and the fruit will be the size you describe. Look closely at the trunk. If you can’t see the bud union where it was grafted onto the rootstock, it has died back below that point. You’ll either need to learn to enjoy the Callery pear as a flowering shade tree, or replace it with a variety of your choosing.