I have a Seville Sour orange that I planted from seed. It is now 8.5 feet in height and after a long wait is producing fruit. The node count on the seed grown tree reached maturity at about 5-feet. Fruit production starts at 5-feet and goes to the very top of the tree. There is no fruit, and will never be any fruit, below the 5-foot mark. The lower portion of the tree, that portion below the required node count for maturity, will forever be immature. The node count where maturity begins for a Seville Sour orange must be approximately at 5-feet, at least it was for this particular tree, and is probably pretty much the same for this variety. .