Red cogongrass | The Morton Arboretum

Red cogongrass is a beautiful grass, but one to be used with care when landscaping. The species, Imperata cylindrica, also known as Japanese blood grass, is a very invasive weed and has been banned or quarantined in a number of southern states. A red-leaved variety of this species is considered non-invasive and is sold under a number of names: Red Baron Japanese blood grass, Imperata cylindrica ‘Red Baron’, Imperata cylindrica ‘Rubra’, Imperata cylindrica var. rubra, and Imperata cylindrica var. koenigii.

This variety was thought to seldom flower and to be sterile when it does flower, but there is little scientific evidence to back this up. The species is a plant that spreads quickly by underground rhizomes. The variety spreads by rhizomes as well, but in a slow fashion. A point of concern is that the variety can revert back to the species and then can become invasive. The variety will show some shade of red on its leaves at all seasons. Any plant that changes to green should be considered a reversion to species and should be removed and destroyed.

Family (English) Grass
Family (botanic) Poaceae
Tree or plant type Grass, Perennial
Native locale Non-native
Size range Medium plant (12-24 inches)
Light exposure Full sun (6 hrs direct light daily)
Hardiness zones Zone 5 (Northern Illinois), Zone 6 (City of Chicago), Zone 7, Zone 8, Zone 9
Soil preference Moist, well-drained soil
Season of interest early winter, midwinter, late winter, early spring, mid spring, late spring, early summer, midsummer, late summer, early fall, mid fall, late fall
Flower color and fragrance Other
Shape or form Upright
Planting considerations Aggressive

Native geographic location and habitat:

Red cogongrass is native to Japan.

Leaf description:

The narrow leaves will grow 1 to 1 1/2 feet tall. When they emerge in spring, the green leaves will be tipped with red. As the season progresses, the color spreads through the leaf and it deepens. By fall the leaves are blood red. In winter, as the plant goes dormant, the leaves will turn a coppery color.

Flower description:

‘Red Baron’ seldom flowers. When the plant does flower, the tiny flowers are held in a spike.

Fruit description:

The small fruit (caryopsis or grains) forms along the spike that held the flowers. Each fruit has a tuft of white hairs attached.

Plant Care:

Best growth is obtained in full sun and a moist, well-drained soil. The plant will grow in light shade but the red color will be diminished. This is a cool season grass, so its most active growth occurs in spring and fall. It will be semi-evergreen in winter and can act as winter interest. Since this grass remains semi-evergreen through winter, it should not be cut back until early spring, before new growth begins. At that time, it can be cut down to the ground if needed or simply trimmed to remove winter damage.

Disease, pests, and problems:

No serious pest problems. Any plant that changes to green should be considered a reversion to the invasive species and should be removed and destroyed.