Chasmanthium latifolium

Among ornamental grasses, Chasmanthium latifolium is the rare one that thrives in shade. River oats, also called northern sea oats and inland sea oats, is a clumping, rhizomatous perennial grass of the eastern and central United States, found in the wild along wooded creek banks, river bottoms, and shaded slopes from Pennsylvania south to Florida and west toward the prairies. The broad, bamboo-like blades are wider than most grasses can claim, and the plant carries them in a loose, arching mound that takes deep shade without sulking.

The glory is the seed heads: flat, drooping spikelets shaped like flattened oats that dangle from thread-fine stems and set the whole plant nodding at the least breath of air. Green through summer, they ripen by way of bronze and coppery tan into autumn, then dry to warm straw that holds well into winter and longer still in a vase, which has long made river oats a favorite for cut and dried arrangements.

In the garden, use this grass to bring movement and light to the places few grasses will grow: a woodland edge, a shaded border, a streamside, or the ground beneath open-canopied trees. Mass for a naturalistic, prairie-meets-woodland effect, or thread among ferns, hostas, and other shade companions for a contrast of texture. River oats seed about with some enthusiasm, welcome where ground wants covering and a minor chore elsewhere, though seedlings pull easily. Native and adaptable, the grass also helps hold a shaded bank against erosion.

Photos courtesy of Joseph A. Marcus