Culture
Easily grown in dry to moist, well-drained soils in full sun to part shade. In warm winter areas, it naturalizes aggressively by both rhizomes and self-seeding to form dense monocultures which displace native species. It is tolerant of shade, poor soils, and drought. It tends to be less aggressive in the cooler conditions of USDA Zones 5-6.
‘Rubra’ is reportedly much less aggressive (shorter plant that spreads slower and does not readily produce seed). It may only be propagated by division.
Noteworthy Characteristics
Imperata cylindrica, commonly known as cogongrass, is now considered to be one of the ten worst weeds in the world. It is native to Korea, Japan, China, India, and tropical eastern Africa. It was introduced into the southeastern U.S. in the early 1900s, unintentionally in the form of packing materials contained in shipping cartons imported into the U.S. and intentionally as a forage grass and/or erosion control plant. This grass is now listed as a Federal Noxious Weed under the Plant Protection Act which means it may not be imported or transported between States without first obtaining a federal permit. It has also been declared a noxious weed by a number of States including Florida, Alabama, Mississippi, North Carolina, South Carolina, Georgia and Hawaii.
This is an opportunistic, rapid-growing perennial grass that spreads invasively in warm winter locations, particularly evident in the southeastern U.S. from South Carolina and Florida to Texas. It is typically found in a number of different sites including roadsides, pastures, mined areas, fields, sand dunes, utility right-of-ways and dry scrubs. It grows in spreading clumps to 2-4’ tall. Yellowish green leaves (to 30” long and to 3/4” wide) feature finely serrated edges, off-center light green to white midribs, and sharp tips. Flowers in cylindrical spikes to 16” long bloom in early spring (March-May), albeit infrequently, in the northern parts of its growing range, but can flower year round in semi-tropical to tropical areas.
Some authorities currently list this grass as being present in five or more varieties, including var. major (the highly invasive variety described herein which is found in the wild in east/southeast Asia and the southeastern U.S.) and var. rubra (non-invasive ornamental red leaved cultivars still sold by nurseries in some states under the common name of Japanese bloodgrass).
Genus name honors Ferrante Imperato (1550-1625) an apothecary (pharmacist) of Naples.
Specific epithet means long and round, cylindrical.
‘Rubra’ (aka var. rubra) is a shorter, less invasive horticultural selection that reportedly rarely flowers, does not set seed and lacks the invasive spreading tendencies attributed to the species. It typically grows much shorter (to 12-18” tall) than species plants. The upper part of each blade turns garnet red in summer, with the red color often deepening toward burgundy as the growing season progresses. Some experts claim, however, that regardless of the tamer tendencies of this red-leaved cultivar/variety, plants can revert to green and quickly reacquire invasive characteristics, hence varietal differences should not be recognized. As an example, ‘Rubra’ may not be legally grown, sold or given away in the State of Alabama.
Problems
No known serious insect or disease problems. Green-leaved species plants are highly invasive.
Uses
Under Federal law, it is illegal to transport cogongrass into or within the United States without first obtaining a permit. Several states have laws forbidding its sale or growth.
Ornamental cultivars (e.g., ‘Rubra’ or ‘Red Baron’) continue to be sold by nurseries in some states. Check State law before purchasing and/or planting ornamental cultivars. Red foliage color can be particularly attractive in the landscape when backlit by early morning or late afternoon sun. May be grown in patio containers or tubs.