Every person who holds a valid license issued by the State of California under the provisions of Chapter 1 (commencing with Section 6721) of the Food and Agricultural Code, authorizing engagement in the business of selling nursery stock in this state, may engage in the preparation of planting plans or drawings as an adjunct to merchandising nursery stock and related products, but may not use the title of landscape architect. That activity is exempt from licensure under the provisions of this chapter.