Ornamental grass
Ornamental grasses are grasses grown as ornamental plants. Ornamental grasses are popular in many colder hardiness zones for their resilience to cold temperatures and aesthetic value throughout fall and winter seasons. Classifications. Along with true grasses (Poaceae), several other families of grass-like plants are typically marketed as ornamental grasses. These include the sedges (Cyperaceae), rushes (Juncaceae), restios (Restionaceae), and cat-tails (Typhaceae). All are monocotyledons, typically with narrow leaves and parallel veins. Most are herbaceous perennials, though many are evergreen and some develop woody tissues. They bring striking linear form, texture, color, motion, and sound to the  garden, throughout the year. Habits. Almost all ornamental grasses are perennials, coming up in spring, from their roots, which have stored large quantities of energy, and in fall or winter go dormant. Some, notably bamboos, are evergreen, and a few are annuals. Many are bunch grasses and tussock grasses, though others form extensive systems of many-branched rhizomes. The bunching types are often called "clump-forming" or "clumping", distinct from the rhizomatous types, called "running". Sizes vary from a few centimeters up to several meters; the larger bamboos may reach 20 m or more tall. Some ornamental grasses are species  that can be grown from seed. Many others are cultivars, and must be propagated by vegetative propagation of an existing plant. Pampas grass ("Cortaderia selloana") is easily recognizable, with semi-dwarf to very large selections for the landscape. Deer grass ("Muhlenbergia rigens") and canyon prince wild blue rye ("Leymus condensatus") are popular in larger settings, natural landscaping, and native plant gardens. There are "Miscanthus" grasses whose variegations are horizontal, and appear even on a cloudy day to be stippled with sunshine. Many "Miscanthus" and "Pennisetum" species flower in mid or late summer, and the seed heads are long lasting, often  remaining well into the winter. Some "Stipa" species flower in the spring, the inflorescence standing almost two metres above the clumps of leaves, and again the seed heads last late into the winter. When gardening near natural wildland-urban interfaces, one should take care to avoid planting invasive species, such as "Cortaderia jubata", "Pennisetum setaceum", and "Nassella tenuissima" (syn. "Stipa tenuissima"), as such is responsible horticulture. Examples. Environmental impact. Some ornamental grasses have become serious invasive weeds, usually as garden escapes into natural vegetation areas.