drafts mature much slower. I wouldn’t until it was at least 3 yrs old. I would ground drive the baby Huey until then. I would add a saddle at 2 yrs old and work with desensitizing and verbal commands.
The draft breeds do tend to take longer to fully mature. Usually at around 6-7 yrs as opposed to 4-5 yrs for most lighter breeds.
At 5 yrs they are fully grown