Question: Why do my pecans not fill out? When the tree was younger they were excellent, but now they only fill out about half way out the kernels.

Answer: That’s a characteristic of several older varieties, most notably Mahan and its daughter Mohawk. Once the trees get large and have heavy yields of pecans, they simply can’t pull enough moisture and nutrients into the roots to supply the needs of the elongating kernels. There isn’t much you can do for them, and, as a result, those varieties simply haven’t been recommended much in recent years.