Thurston County, WA Tree Protection: Heritage & Protected Trees (2026)

Under Thurston County Code 17.27.400, a "heritage tree" is any tree over forty inches DBH, or one that is historically or culturally significant at any size and listed by recognized community groups or tribal nations. Applicants for Class IV-General forest practices development must retain at least seventy percent of heritage trees on site, and every retained heritage tree must be shown to be windfirm. Heritage trees keep credit toward the county's minimum tree-unit density (100 units/acre) even if damaged or in poor health, and a qualified forester must document them by species and DBH in the required tree conservation plan. The rule applies to development requiring a Class IV-General forest practices permit; it exempts multifamily, commercial and industrial projects covered by Title 18/20 landscaping standards, platting/subdivision applications, and public infrastructure work.