Tsuga heter. 'Iron Springs' HemlockTsuga heterophylla Iron Springs has short, dark green needles that contrast well with the light bark on the very irregular branches of this choice selection of Western Hemlock. It eventually develops a rigid, upright broad habit, but it grows more slowly than the species. Found at Iron Springs, Washington, and introduced by the University of Washington. Garden Size: 12H x 8W Intermediate: 6 10 year Broad Upright Zone 6