Ask-a-Dave's-Gardener: Prune low mulberry branches?, 1 by Adamantya

Adamantya wrote:
Hi there,

This tree was a whip a mere 3 years ago and has been fruiting (delicious and prolific!) for 2 summers. The speed of growth is unbelievable; we haven\'t fertilized or anything.

There is one branch growing horizontally quite low to the ground, about a foot and a half off the ground (lower right corner of photo). Will it rise up the trunk as the tree grows, or will it stay low? Should I prune it off? Many thanks!