Japanese Blood Grass or Cogon Grass

Imperata cylindrica is a species of perennial rhizomatous grass native to tropical and subtropical Asia, Micronesia, Melanesia, Australia, Africa, and southern Europe. It has also been introduced to Latin America, the Caribbean, and the southeastern United States. Cogon grass is highly flammable, contributing to many wild fires. The chemicals in the grass cause the fires to burn hotter than normal, killing the surrounding trees and vegetation. The blades of the grass burn but the rhizome from which they grow is able to survive the heat of the fire and grow foliage afterwards. This allows it to spread and colonize burned or disturbed areas, replacing the original plants.

They are finely toothed and embedded with sharp silica crystals. The rhizomes are extensive and can penetrate 2-4 feet deep. It rarely flowers in its northern range. In more tropical areas it freely flowers with 16-inch panicle inflorescences. Flowers are fluffy, silvery-white spikelets. Its foliage starts off green with faintly tinted crimson tips. As it ages, it turns into the plant’s signature blood red. The plant has become naturalized in the Americas, Northern Asia, Europe and Africa in addition to many islands and is listed as an invasive weed in some areas. There is no serious insect or disease problems.

Table of Contents


1 - 10 feet

Width-Circumference (Avg)

0.8 - 1 feet

Approximate pH

6.5 - 7.5

Varieties of Japanese Blood Grass

Because of its invasive tendencies, gardeners should take care to purchase only the named, sterile cultivars, which include 'Red Baron' and 'Rubra.' These grasses don't look different from the species, but have the important attribute of forming few or no flowers, and spreading slowly by rhizomes rather than quickly taking over the flowerbed.

Planting Japanese Blood Grass

Preparing Garden Beds

Use a soil testing kit to determine the acidity or alkalinity of the soil before beginning any garden bed preparation. This will help you determine which plants are best suited for your site. Check soil drainage and correct drainage where standing water remains. Clear weeds and debris from planting areas and continue to remove weeds as soon as they come up.

A week to 10 days before planting, add 2 to 4 inches of aged manure or compost and work into the planting site to improve fertility and increase water retention and drainage. If soil composition is weak, a layer of topsoil should be considered as well. No matter if your soil is sand or clay, it can be improved by adding the same thing: organic matter. The more, the better; work deep into the soil. Prepare beds to an 18 inch deep for perennials. This will seem like a tremendous amount of work now, but will greatly pay off later. Besides, this is not something that is easily done later, once plants have been established.

Growing Japanese Blood Grass From Seeds

The desirable named cultivars of Japanese blood grass do not produce viable seeds. It isn't recommended to grow seeds of the invasive species type.

Japanese Blood Grass Care

Japanese blood grass is an easy-to-grow ornamental grass that provides reliable color as the season progresses. The serrated foliage is unattractive to deer and rabbits, and the rapid growth habit fills in hillsides quickly to help with erosion control. This vigorous plant needs little care to thrive. However, keep an eye on blood grass, as it can quickly get out of hand.


Japanese blood grass shows its best coloration in full sun, at least six hours of direct sun per day. In Southern gardens, some afternoon shade is tolerated.


Provide your Japanese blood grass with moist, well-drained soil. The plants grow well in sandy soils, and can even thrive in coastal gardens.


Japanese blood grass grows vigorously in the presence of moist soils, but it tolerates drought conditions as well. Only irrigate the plant as necessary to prevent the browning of foliage.

Temperature and Humidity

Japanese blood grass grows well in a wide range of temperatures. In the warmer reaches of its zone boundaries, the plants can spread and displace other garden plants with their rhizomes. Both humid and dry conditions are tolerated by the grasses.


No fertilizer is needed to grow Japanese blood grass successfully, as the plants will grow in poor soil. Extra nutrients may cause the grass to grow aggressively.

Pruning and Propagating Japanese Blood Grass


Japanese blood grass plants look attractive throughout the winter months and may be somewhat evergreen in most climates. Leave the plants standing until spring, and then cut them back, or just trim away dead foliage.

Propagating Japanese Blood Grass

Japanese blood grass is easy to propagate by division, even for beginners. Cut into the plant with a spade in the spring or fall, when growth is most active. Don't be afraid to make many small divisions as needed, as the plants will grow and mature rapidly.

Potting and Repotting

Japanese blood grass isn't picky about potting soil or container types. Grasp the plant by the root ball and loosely pack the potting medium around the plant. Repot in the spring or fall as needed when plants become crowded with spreading rhizomes.


No special care is needed for overwintering this plant. The colors stay vibrant through cooler temperatures, so many leave it alone and cut it back in early spring.

Common Problems with Japanese Blood Grass

Japanese blood grass isn't bothered by any pest or disease problems. Plants that revert to green should be removed to avoid significant invasive habits.


  • It is used for thatching the roofs of traditional homes throughout south-east Asia.

  • It is used in traditional Chinese medicine.

  • It is planted extensively for ground cover and soil stabilization near beach areas and other areas subject to erosion.

  • Other uses include paper-making, thatching and weaving into mats and bags.

  • Young inflorescences and shoots may be eaten cooked, and the roots contain starch and sugars and are therefore easy to chew.

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