Question: I think my fruit trees have mutated. My pear tree has thorns and little round fruit, and my plum fruit isn’t the right color.

Answer: That can be one of two things, but it’s not usually mutation. In the case of your pear, the top of the original tree has died out. What you have now is the growth of Callery pear, the rootstock onto which pears are grafted. It’s a lovely shade tree, although its fruit is not edible and the plant does have thorns. You need to plant a new tree of the variety you wanted. As for the plum, you probably got a tree that was mis-labeled at the nursery.