California Code, Business and Professions Code - BPC § 5659

Each person licensed under this chapter shall sign, date, and seal or stamp using a seal or stamp described in this section, all plans, specifications, and other instruments of service therefor, prepared for others as evidence of the person's responsibility for those documents.  Failure to comply with this section constitutes a ground for disciplinary action.  Each person licensed under this chapter shall use a seal or stamp of the design authorized by the board, bearing the person's name, license number, the legend “licensed landscape architect,” the legend “State of California” and a means of providing a signature, the renewal date of the license, and date of signing and sealing or stamping.