Normal for Vertical Limbs to Become Horizontal

Q.  My Seville orange tree has been growing in my yard for 20+ years. About a month ago, I noticed one of the branches that grew straight up is now parallel to the ground. Any idea what caused this?

 

Pomegranate growth is a little different from citrus growth. But there are similarities. According to the owner of this tree, it has not yet flowered and fruited. Its branches are vertical. After it begins fruiting the weight of the fruit will pull the branches to a horizontal position.

A. The reason upright limbs of fruit trees with large fruit become horizontal is from the weight of the fruit. The fruit tree which demonstrates this the best is pomegranate.

This orange tree has not yet produced fruit. Its major branches are vertical.

            The upright shoots of pomegranate bend nearly horizontal after they flower and bear fruit. The weight of the fruit bends the branches downward. To a lesser degree we see this in ornamental trees and nut trees as well as they get older.

This fifteen-year-old pomegranate tree has produced an abundance of heavy fruit. The fruit has waited the branches and open the canopy. Opening the canopy allows more sunlight to enter it and the tree produces more fruit. Relate this back to natural selection and evolution.

            In these cases, the weight of the branch as it gets longer and heavier begins to bend the branch into a more horizontal position. Often times young trees are described as being "upright or semi upright" while the mature forms of the tree may be called vase shaped or even round.