I have a very weak walnut tree (Mother Nature or a squirrel planted it). The limbs have been falling off easily soon after they're grown. Last year a storm took off the top 6 inches or so (the tree is around 8 ft tall now) and another limb is semi taking it's place. In a storm today, another limb (about 3/4 inch across where it meets tree) wripped off partially. I had to cut it loose before it stripped the bark off. It's very flimsy in a good wind. What kind of tree is stronger when it's young?