Cal. Health and Safety Code § 14900.6

In the case of weeds which have previously been declared to constitute a seasonal and recurring nuisance, it is sufficient to mail a post card notice to the owners of the property as they and their addresses appear upon the current assessment roll. The notice shall refer to and describe the property and shall state that noxious or dangerous weeds of a seasonal and recurrent nature are growing on or in front of the property, and that the same constitute a public nuisance which must be abated by the removal of said noxious or dangerous weeds, and that otherwise they will be removed and the nuisance will be abated by the county authorities, in which case the cost of such removal shall be assessed upon the lot and lands from which or in front of which such weeds are removed and that such cost will constitute a lien upon such lots or lands until paid.