I live in AZ and we planted a grapefruit tree a few months ago. There were a few baby grapefruit growing. Should we have cut them off so it can use all its energy on growing roots or does that not apply to trees?
Yes, you are correct.
You should remove any fruit that may be on or forming on your young Grapefruit Tree.
You want your new tree to spend it's energy settling in and growing strong roots.
You can strip the fruit for the first year or two.