Rev. & Tax. Code, § 53

(a) Except as provided in subdivision (b), the initial base year value for fruit and nut trees and grapevines subject to exemption pursuant to subdivision (i) of Section 3 of Article XIII of the California Constitution shall be the full cash value of those properties as of the lien date of their first taxable year.

(b) A county board of supervisors may, after consulting with affected local agencies within the county’s boundaries, provide by ordinance that the initial base year value for replacement grapevines that are planted to replace grapevines less than 15 years of age that were removed solely as a result of phylloxera infestation or Pierce’s Disease, and are planted on the same parcel as the replaced grapevines, as certified in writing by the county agricultural commissioner, shall be the base year value of the removed grapevines factored to the lien date of the first taxable year of the replacement grapevines. The assignment of base year replacement value shall be limited to that portion of the replacement grapevines that are substantially equivalent to the grapevines that were replaced, if the replacement grapevines are planted at a greater density.