 The gardens are named after Thelma and Charles Mercer, who purchased in the late 1940s for their home and garden.They preserved native trees such as dogwoods, palmettos, rusty blackhaw viburnum, and hawthorns, and introduced camellias and exotic tree species such as ginkgo, bauhinia, philadelphus, camphor, and tung oil.The property was purchased by Harris County in 1974, and has grown to .