Low-lying wet areas of a garden require special kinds of plants. Many trees, shrubs and other perennials need well-drained soil, but some plants prefer moist to wet or boggy soil. Water-loving ornamental grasses provide a serene landscape with their waving plumes floating above their mounds of grassy foliage.
Each ornamental grass has specific cultural requirements, with sunlight being just as important as soil's moisture level. Prairie cordgrass (Spartina pectinata), which is a native species, and the sugarcane plumegrass cultivar 'Red Mountain' (Erianthus giganteus 'Red Mountain') thrive in full-sun locations with moist to wet soil. A warm-season plant, prairie cordgrass grows up to 5 feet tall plus an additional 2 feet when it flowers in fall. It grows as a perennial, or is hardy, in U.S. Department of Agriculture plant hardiness zones 4 through 9. 'Red Mountain' sugarcane plumegrass is also a warm-season grass. Hardy in USDA zones 6 through 8, it grows 2 to 3 feet tall in mounds and has late-fall flowers, the stalks of which reach 6 to 7 feet tall.
Other sun-loving varieties that do well in moist to wet soil include:
- Blue love grass (Eragrostis chloromelas, USDA zones 7 through 9), with foliage growing 3 feet tall and flower stalks up to 4 feet tall.
- Bushy bluestem (Andropogon glomeratus, USDA zones 5 through 9), growing foliage up to 4 feet tall and flower stalks 6 feet tall.
- Grassy-leaved sweet flag cultivar 'Ogon' (Acorus gramineus 'Ogon,' USDA zones 5 through 9), which grows 6 to 12 inches tall and has inconspicuous flowers.
- Indian grass (Sorghastrum nutans, USDA zones 2 through 9), with foliage 3 to 4 feet in height and flower stalks 5 to 8 feet tall.
- ‘Northern Lights’ tufted hair grass (Deschampsia caespitosa 'Northern Lights,' USDA zones 4 though 9), which grows up to 1 foot tall and does not flower.
Some ornamental grasses that thrive in wet or moist soil thrive in partial or dappled shade, making them suitable for gardens under tree canopies or other areas shaded from afternoon sun. An example is the cool-season grass Canada bluejoint (Calamagrostis canadensis, USDA zones 3 through 8). Its foliage grows 2 feet tall, and flowering plumes add another 2 feet of height to this North American native. Variegated river oats (Chasmanthium latifolium 'River Mist,' USDA zones 5 through 9), another example, adds color to a partial-shade or shade garden with its 2 1/2-foot-tall, green-and-white-striped blades. It is a warm-season grass.
Other ornamental grasses and grasslike perennials that thrive in moist to wet, partial-shade sites include:
- 'Evergold' variegated Japanese sedge (Carex oshimensis 'Evergold,' USDA zones 5 through 9), growing 6 to 8 inches tall with small flowers.
- Fox sedge (Carex vulpinoidea, USDA zones 3 through 7), which grows 1 to 3 feet tall.
- Gray's sedge (Carex grayi, USDA zones 3 through 9), with foliage growing 2 feet tall and flowers reaching up to 3 feet tall.
Many of the shade-loving ornamental grasses thrive in woodlands along creeks and rivers, where the soil is consistently moist and rich with organic matter. Virginia wild rye (Elymus virginicus, hardy in USDA zones 3 through 9) is one of them. Its foliage grows up to 3 feet tall; when it blooms in spring, the plumes rise to 4 feet tall. It tolerates soil conditions ranging from moist to wet with occasional dry spells. Hakone grass (Hakonechloa macra, USDA zones 4 through 7) also thrives in shade. It is a warm-season grass that grows 1 1/2 to 2 feet tall. Additional ornamental grasses for shady moist to wet locations include:
- Bronze veil tufted hair grass (Deschampsia cespitosa 'Bronzeschleier,' USDA zones 4 through 9), with 1-foot-tall foliage and flower plumes up to 3 feet tall.
- Golden variegated hakone grass (Hakonechloa macra 'Aureola,' USDA zones 4 through 7), which grows 1 1/2 to 2 feet tall.