Cal. Gov. Code § 39562.2
In any case where cities are authorized to abate weeds pursuant to the provisions of this chapter and where the legislative body finds and declares that weeds on specified parcels of property are seasonal and recurrent nuisances as provided in Section 39562.1, the legislative body may provide for the preventive abatement of such seasonal and recurrent nuisance as provided in this section.
The notice required by Section 39562.1 shall, in addition to containing all other required matters, state that the efficient and economical control of such seasonal and recurrent nuisance requires preventive chemical control of such weeds, weed seeds and weed seedlings and that the city may require preventive chemical control of such nuisance.
In the event the city is once required to abate such nuisance the city may, in addition, before and during the next following germinating season of such weeds, provide for the preventive abatement of such nuisance by using chemical control of such weeds.
Ca. Gov. Code § 39562.2