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Imperata spp.
cogongrass
Old World tropics and subtropics; one species in the Americas
Overview
Imperata is a genus of about eight rhizomatous perennial grasses in the family Poaceae, distributed across warm-temperate and tropical regions worldwide. Plants spread by tough, creeping rhizomes to form open colonies, with flat, upright leaf blades 12-48 inches (30-120 cm) tall depending on species and growing conditions. I. cylindrica, the most widespread species, produces silvery, cylindrical flower plumes 2-8 inches (5-20 cm) long in summer; its red-leaved selections, sold as Japanese blood grass, turn from green at the base to deep blood-red toward the tips through the season. The narrow leaves have an off-center pale midrib and finely saw-toothed edges. In the wild the genus grows in grassland, open woodland, roadsides, and disturbed ground, often on poor or sandy soils, and the running rhizomes let it form dense stands. The green form of I. cylindrica (cogongrass) is a regulated noxious weed across the southeastern United States and many tropical countries, where it displaces native vegetation and carries fire. Ornamental red selections are restricted in several states because they can revert to the invasive green form.
Native Range
Imperata spp. occurs across the warmer regions of the Old World, native through Africa, southern Europe, Asia, and Australia, with one species in the Americas. I. cylindrica is native to Asia and Africa and has become naturalized and invasive in the southeastern United States and other warm regions.Suggested Uses
Imperata spp. red selections are grown in borders, gravel gardens, and containers for their colored foliage, often backlit where the red blades catch sun. Because of its spreading rhizomes and weed status, it is kept in contained plantings rather than open ground in warm climates.How to Identify
Appearance
Size & Dimensions
Height1' - 4'
Width/Spread1' - 3'
Bloom Information
Imperata spp. flowers in summer, producing slender, silvery-white cylindrical plumes packed with silky-haired seeds. Wild I. cylindrica flowers and seeds freely, while the cultivated red forms rarely bloom in cooler climates. The plumes catch light and persist for several weeks before shedding seed.
Detailed Descriptions
Foliage Description
green, red-tipped in colored formsGrowing Conditions
Sun Requirements
Requires 5-10 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Grow Imperata spp. in full sun to light shade on moist, well-drained soil; it tolerates poor, sandy ground and some drought once established. The red selections develop the deepest color in full sun and stay greener in shade. Water during dry spells to keep growth steady, and cut old foliage to the ground in late winter before new shoots emerge. The running rhizomes spread steadily, so the plant is often confined to a sunken container or root barrier. I. cylindrica in its green form is banned from sale and movement in many regions under noxious-weed laws.Pruning
Imperata spp. needs only an annual cut, removing the previous year's foliage to the ground in late winter or early spring. Any shoots that revert to plain green on red-leaved forms are dug out, as the green form is the invasive type. Division in spring controls spread and renews vigor.Container Growing
✓ Suitable for container growing
Minimum container size: 3 gallons