San Mateo County, CA Cannabis Regulations: Home Cultivation (2026)

California Proposition 64 (2016) and the Medicinal and Adult-Use Cannabis Regulation and Safety Act (MAUCRSA, 2017) allow adults 21+ to cultivate up to 6 plants per residence. Unincorporated San Mateo County adopted Chapter 5.148 restricting personal cannabis cultivation as follows: permitted only indoors inside a private residence or a fully enclosed, secure accessory structure on the residential grounds; outdoor cultivation (visible or not) is expressly PROHIBITED countywide. The indoor area must be locked and secured from unauthorized access including by minors. Odor must be controlled so it does not drift off-site (carbon filters or sealed systems). Electrical modifications for lighting, ventilation, or climate control require building/electrical permits. Qualified medical patients with a physician's recommendation may cultivate for personal medical use under the same indoor-only restrictions; there is no enhanced plant count. Landlords may prohibit cannabis cultivation in rental units per lease terms. HOAs may also prohibit. Cultivation for sale or distribution without a commercial license is a crime under H&S Code §11358.