Wash. Rev. Code § 17.06.030
Any one or more freeholders owning more than fifty percent of the acreage desired to be included within the proposed intercounty weed district may file a petition with the principal board of county commissioners praying that their land be included, either separately or with other lands included in the petition, in a weed district to be formed for the purpose of destroying, preventing or exterminating any one or all such weeds, or that such lands be included within a district already formed, or a new district or districts to be formed out of any district or districts then existing. Such petition shall state the boundaries of the proposed district, the approximate number of acres in the proposed district, the particular weed or weeds to be destroyed, prevented or exterminated, the general method or means to be used in such work, and shall contain a list of all known landowners within the proposed district, together with the addresses of such landowners. Upon the filing of such petition the principal board of county commissioners shall notify the other boards of commissioners, shall arrange a time for a joint hearing on the petition, and shall give at least thirty days' notice of the time and place of such hearing by posting copies of such notice in three conspicuous places within the proposed district, and at the main entrance to the courthouse of each county, and by mailing a copy of such notice to each of the landowners named in the petition at the address named therein. If any of the land described in the petition be owned by the state a copy thereof shall be mailed to the department of natural resources at Olympia.
RCW 17.06.030