Japanese Blood Grass: A Vibrant Ornamental with Invasive Potential
Introduction
Japanese blood grass (Imperata cylindrica) is a striking ornamental grass known for its vibrant red foliage. While it can add a touch of color to gardens, it’s essential to be aware of its invasive potential and take steps to control its spread.
Characteristics
- Botanical Name: Imperata cylindrica
- Common Name: Japanese blood grass, cogongrass
- Plant Type: Perennial
- Mature Size: 1 – 2 ft.
- Sun Exposure: Full
- Soil Type: Moist but well-drained
- Soil pH: Acidic, alkaline (6.5-7.5)
- Hardiness Zones: 5, 6, 7, 8, 9
Cultivation
Light
Japanese blood grass thrives in full sun, receiving at least six hours of direct sunlight daily. In warmer climates, some afternoon shade is acceptable.
Soil
Provide your blood grass with moist, well-drained soil. It grows well in sandy soils and even tolerates coastal garden conditions.
Water
Japanese blood grass is a vigorous grower that prefers moist soils. However, it can also tolerate drought conditions. Water the plant only as necessary to prevent the browning of foliage.
Temperature and Humidity
This grass grows well in a wide range of temperatures. In warmer climates, it can spread and displace other plants with its rhizomes. Both humid and dry conditions are tolerated.
Fertilizer
Japanese blood grass does not require fertilizer to thrive. Excessive nutrients may cause the grass to grow aggressively.
Invasive Potential
While the red form of Japanese blood grass is technically not invasive, it can easily revert to the green form, which is considered one of the most invasive weeds in the world. Some states have declared the green form a noxious weed due to its ability to spread rapidly and outcompete native plants.
Control Methods
- Choose sterile cultivars: Plant named, sterile cultivars such as ‘Red Baron’ or ‘Rubra.’ These grasses have few or no flowers and spread slowly by rhizomes.
- Container culture: Growing Japanese blood grass in containers can help prevent it from spreading into the surrounding area.
- Physical removal: Remove any plants that revert to green to prevent them from spreading.
Propagation
Japanese blood grass is easy to propagate by division. Cut into the plant with a spade in the spring or fall when growth is most active. Divide the plant into as many small divisions as needed, as they will grow and mature rapidly.
Overwintering
Japanese blood grass requires no special care for overwintering. The colors stay vibrant through cooler temperatures, and it can be left alone and cut back in early spring.
Common Problems
Japanese blood grass is not typically bothered by pests or diseases. However, it’s important to remove any plants that revert to green to prevent them from becoming invasive.
Frequently Asked Questions
- Can Japanese blood grass grow indoors?
Container culture is best for regions at risk of the weedy potential of Japanese blood grass. Combine it with trailing plants or flowers.
- What is an alternative to Japanese blood grass?
Purple fountain grass offers a similar look with its dark purple stems and bronzy plumes. It is a tender perennial often treated as an annual.
- How do I grow Japanese blood grass from seeds?
The desirable named cultivars do not produce viable seeds. It is not recommended to grow seeds of the invasive species type.
- How do I repot Japanese blood grass?
Repot the grass in the spring or fall as needed when plants become crowded with spreading rhizomes. Use any type of potting soil or container.
- How do I overwinter Japanese blood grass?
No special care is needed for overwintering. The colors remain vibrant, and the grass can be left alone and cut back in early spring.
