Several varieties of ornamental grasses are available in the seven foot and higher range. Goliath (Miscanthus sinensis) reaches seven feet tall with mahogany-colored flowers and blooms in August. Giant feather grass (Stipa gigantea) stretches to a showy seven feet in clumps with narrow gray-green leaves and airy white flowers. Ravenna grass (Saccharum ravennae) provides nine-foot stems and gray-green mounding foliage with feathery plumes. It turns reddish bronze in autumn.
Big bluestem (Andropogon gerardii) grows in a narrow column form to six feet. Its blue-green in summer and turns russet in the fall. Feather reed grass (Calamagrostis acutiflora), commonly known as "Karl Foerster," also grows narrow and upright but only to four or five feet. It tolerates light shade and moist soil well, and displays soft white flowering at the head. Maiden grass (Miscanthus sinensis), "Kleine Fontaine," matures at five feet with silver flowers turning to pink.
Variegated purple moor grass (Molinia caerulea) grows in stiff green and yellow leaves to 18 inches tall. It tolerates shade well and displays purple flowers. It is often referred to as Variegata. Tufted hair grass (Deschampsia cespitosa), commonly called "Northern Lights," has pretty pink tips on top of green and white leaves. It grows in 12-inch clumps. Japanese blood grass (Imperata cylindrica), commonly tagged as "Red Baron," has bright red, erect 18-inch leaves. It spreads slowly and grows in part shade.
There are approximately 100 varieties of grasses known as ornamental. Each micro-climate in Washington will have types that grow the best. Before choosing, consult with the county agricultural extension agent or an established local nursery. Their advice will lead to consistent success as it is tuned to the local environment.