As of November 8, 2016, adults in California over the age of 21 can grow up to 6 plants per household.
Prop 64 permits adults 21 years of age and over to possess and grow specified amounts of marijuana for recreational use:
(1) A person shall plant, cultivate, harvest, dry, or process plants in accordance with local ordinances, if any, adopted in accordance with subdivision (b).
(2) The living plants and any marijuana produced by the plants in excess of 28.5 grams are kept within the person’s private residence, or upon the grounds of that private residence (e.g., in an outdoor garden area), are in a locked space, and are not visible by normal unaided vision from a public place.
(3) Not more than six living plants may be planted, cultivated, harvested, dried, or processed within a single private residence, or upon the grounds of that private residence, at one time.
For fines and violations for abusing the rules, CLICK THIS LINK.