Unincorporated San Mateo County allows adults 21+ to cultivate up to 6 cannabis plants per residence for personal, non-medical use under County Code Chapter 5.148 (Personal Cultivation). Cultivation must occur inside a private residence or a fully enclosed and secure accessory structure — OUTDOOR personal cultivation is PROHIBITED in unincorporated San Mateo County, going further than state law's baseline. Qualified medical patients may also cultivate indoors. Sale or commercial distribution requires a commercial cannabis license, which the County does NOT issue for retail activities.
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.
Outdoor personal cultivation: County Code Chapter 5.148 violation, $100-$500 first offense, escalating for repeat. Exceeding 6 plant limit: citation and plant abatement. Unsecured cultivation accessible to minors: misdemeanor H&S §11357.5. Cultivation for sale without license: felony H&S §11358. Unpermitted electrical work: building code violation plus possible fire code liability.
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