Oleander is an unincorporated community in Fresno County, California. It is located 9 miles south-southeast of downtown Fresno, at an elevation of 285 feet. A post office operated at Oleander from 1881 to 1935, moving in 1899. The name honors its first …Oleander is an unincorporated community in Fresno County, California. It is located 9 miles south-southeast of downtown Fresno, at an elevation of 285 feet. A post office operated at Oleander from 1881 to 1935, moving in 1899. The name honors its first postmaster, William Oleander Johnson.