Cal. Government Code § 25921

The board of supervisors may sell at a price not less than the county’s estimated cost, surplus plants, shrubs, flowers, trees, and vegetation, and their seeds or products, produced at a county arboretum. The board may also exchange such materials for other materials of approximately the same value with any person, entity, political entity, or nation, or may distribute such materials without charge to any person, entity or political entity in this state for the purpose of testing such materials under conditions not obtainable at the county arboretum, if in the discretion of the board of supervisors such exchange or testing will benefit the arboretum or facilitate the accomplishment of the purposes specified in Section 25920. No such plant, shrub, flower, tree, seed or their product may be sold if such plant, shrub, flower, tree, seed or their product is available commercially within the State of California. In addition to the other powers herein granted, the board may exercise any other powers it deems necessary and proper to promote the objects and purposes of the county arboreta.