Imperata cylindrica Seeds | Rhizome of Wooly Grass Bai Mao Gen
LATIN NAME: Imperata cylindrica
COMMON NAME: Bai Mao Gen, Cogon Grass Rhizome, White Grass Root
Plant Profile
Bai mao gen is the rhizome of cogon grass, Imperata cylindrica, one of the most widespread grasses in the warm world and one of the hardest to remove from a garden. It grows in tufts of stiff, upright leaves half a metre tall, with a feathery white seed head that gives the plant its Chinese name, white grass.
The useful part runs underground: a pale, jointed rhizome that spreads horizontally, pushing up new shoots every few centimetres. It is sweet and cooling in taste, and it is used in Chinese medicine as a hemostatic. The leaf blades are rough to the touch, with a prominent midrib, and they stay green into winter in mild climates. The seed head persists into winter, which is how the plant is usually spotted from a distance.
Science & Biotechnology
The rhizome contains triterpenoids, including cylindrin and arundoin, together with flavonoids and a high concentration of potassium salts. The potassium content is probably why a decoction tastes faintly salty and why it has a mild diuretic effect.
The hemostatic use has been investigated in animal models of bleeding time, with modest results. The plant’s more consequential chemistry is ecological: cogon grass exudes allelopathic compounds that suppress neighbouring seedlings, which is one reason it forms monocultures so quickly after disturbance. The rhizome also accumulates silica, which is one reason a decoction feels slightly slick. In warmer regions the plant flowers almost continuously and sets very little seed, which is another reason the rhizome does the spreading.
Uses & Benefits
Dried rhizome is decocted at nine to thirty grams for nosebleeds, blood in the urine and thirst with fever, often combined with reed rhizome. Fresh rhizome is juiced in some traditions, which is a stronger preparation.
Because the plant is a serious invasive weed in tropical and subtropical countries, it should never be planted in the open ground outside its native range. The ornamental form sold as Japanese blood grass, with red tips, is the same species and is banned in several American states for that reason. Fresh rhizome is sold in bundles in southern Chinese markets through the summer.
Growing from Seed
Seed is rarely viable and is not the way to propagate it. Rhizome sections of five centimetres, each with two buds, will establish in almost any soil and any light level, which is exactly the problem.
If it is grown at all, it should be in a buried container with a rim above soil level. Even then, rhizomes travel under paving and through mulch. Digging out the plant requires removing every fragment; a single node regenerates a new clump within a season. Frost kills the leaves but not the rhizome, which regrows in spring from the same network. The rhizome is best lifted in late summer, when the sugar content is highest and the joints are easy to separate.
Our Take
A useful medicine and a notorious weed, best grown in a pot with the rim above ground and never turned loose in a garden.
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