I'd assume that if you have your recommendation, you could grow but every county has their own set of guidlines.

California State Guidline H&SC 11362.77 (a) says "A qualified patient or primary caregiver may possess no more than eight ounces of dried marijuana per qualified patient. In addition, a qualified patient or primary caregiver may also maintain no more than 6 mature or 12 immature plants per qualified patient"

That's just the state guidline though. The county might have their own set of rules, and federal...well, we all know none of this flies with the feds.