Standard:
Grow up to 30 feet tall
Space 25 to 30 feet apart

Semi-Dwarf:
Grows 12 to 20 feet tall
Space 15 feet apart

Dwarf:
Grows 6-10 feet tall
Space 8-10 feet apart

Harvest:
The best way to know if apples are ready for harvest is to taste them.  Apples are usually ready for harvest when they reach full color; full color may vary according to the variety. A mature apple will easily come away from the tree, lift the apple, and twist in a rotating motion.

For more information on growing Apples check-out this great guide from Harvest To Table:
https://harvesttotable.com/how_to_grow_apples/