Frequently asked questions Can qualifying medical marijuana patients in Washington grow cannabis? If a qualifying patient has not been entered into the medical marijuana authorization database, he/she may grow, in his or her domicile, up to 4 plants for the personal medical use of the qualifying patient and 6 possess up to six ounces of useable marijuana in his or her domicile. Those entered in the state’s voluntary patient database may cultivate, in his or her domicile, up to 6 plants for the personal medical use and possess up to 8 ounces of useable marijuana produced from his or her plants. If the patient’s healthcare practitioner determines the patient requires more than the presumptive amount, they may authorize: Up to 15 plants for personal medical use, and May possess 16 ounces of usable marijuana produced from their plants. Note: No more than 15 plants may be grown or located in any one housing unit even if multiple qualifying patients or designated providers reside in the housing unit. The only exception will be for cooperative gardens established under SB 5052.