Or it could be much faster. I grew some crabapples from seed. I started them in the winter under lights in 18s and did 2 transplants into 1 and then 3 gal RB2s in the first growing season and planted them in the field the next fall. Of about 8 trees, one of them had some crabapples on it during the second growing season. I'm guessing that was fairly unusual, but it can happen.
With most of the crabs I'm growing from seed, I'm grafting them in the field to a known variety but leaving a nurse branch. It will serve as a pollinator and eventually I'll see what kind of apples that seedling produces. If I particularly like the characteristics, that nurse branch will become a scion source for other seedlings or clonal rootstock depending on the situation.
Thanks,
Jack