California Code, Food and Agricultural Code (Formerly Agricultural Code) - FAC § 14538

“Hydroponics” means a system in which water soluble primary or secondary plant nutrients or micronutrients, or combination thereof, are placed in intimate contact with the plant's root system, being grown in a water or an inert supportive medium which supplies physical support for the roots but which does not add or subtract primary or secondary plant nutrients or micronutrients, or both.