Can I grow marijuana in California with an MMJ Card?

Yes, a Medical Marijuana patient or their caregiver can grow up to six mature plants, 12 immature plants or a greater amount consistent with the patient's reasonable needs.

To grow more than this, you will need to obtain what is called a 99 plant growers recommendation. A permit can be obtained through a Leafwell doctor if required, as an adendum to your doctor's recommendation.