- Type
- Herbs & Aromatics
- Difficulty
- Easy
- Season
- Spring
- Sowing
- From rhizome
Cogon grass
Imperata cylindrica
Sugars and triterpenes · white plumes across a sunny bank
Cogon grass is a perennial grass that stands in colonies on sunny banks, levees and around grave mounds. In April and May silvery white plumes come up, and the young flower spike before it opens — ppilgi — is what children used to pull and chew. Underground it runs a long white, jointed rhizome, and that rhizome dug and dried is baengmogeun. The Donguibogam lists it in the Herb section as 茅根, records the Korean name as ttippuri, and states plainly that this is 白茅根. It gives a cold nature, a sweet taste and no toxicity, and adds that the root is dug in the sixth lunar month and dried in the sun. The rhizome is still simmered as a tea today, and the dried leaves once thatched roofs and were woven into rain capes. The rhizome travels so far, though, that many countries list the plant as a difficult weed, so in a plot it belongs in a pot.
Year-Round Calendar
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Where It Grows
- Main producer The largest volume of dried rhizomes in trade comes from here. They are dug on sunny slopes in Central and South China.
- Wild population Common nationwide on sunny banks, embankments, and around gravesites.
- Wild population Common in sunny grasslands and on riverside flats from Honshu southward.
- Wild population Common in grasslands and abandoned fields across the subcontinent, and also used as a thatching grass.
It is an Old World grass of the pantropical and temperate zones, ranging from East Asia through Southeast Asia and India to Africa and southern Europe. It has also spread into southeastern North America and Oceania, but there it is treated as an invasive species to be controlled rather than a product, so those regions are not counted among producing areas. Because it is not a field crop but a wild grass dug from where it grows naturally, there are no national production statistics.
- Optimum
- 20~30℃
- Range
- 5~35℃
- Hardiness
- Hardy
It favors dry banks and embankments that get sun all day long. It is highly tolerant of heat and drought; the above-ground parts die back in winter, but the underground rhizomes survive unfrozen and sprout again the following year. In shade it will not send up flower spikes.
Harvested 2–3 years after planting. If rhizomes are planted in spring, the flower spikes — the ppilgi — generally begin to come up from the following spring, and rhizomes thick enough to dig come from clumps that have grown for two or three years.
In Korea Nationwide
It grows nationwide wherever there are sunny banks, embankments, or gravesites. The young flower spikes, known as ppilgi, are pulled in April–May, and the rhizomes are dug in summer.
How to grow
- Light
- Full sun all day. In shade it does not throw plumes
- Soil and depth
- Lean, free-draining ground suits it. Sandy bank soil is plenty
- Spacing
- Always fix the boundary with a pot or a barrier. Planted straight into the ground, the rhizome runs in every direction
- Watering
- Keep it from drying out through the first year only. Once rooted it stands drought
- Feeding
- No feeding. Rich ground gives long leaf and a soft rhizome
- Harvest
- Pull ppilgi in April and May before the spike opens. Dig the rhizome in summer, wash off the soil, trim the fine roots and dry it in the sun
What makes the difference. Dry the dug rhizome whole and cut it afterwards. Only fully dried pieces go into a sealed container, or mould follows
Why this one is harder. The work here is containment, not cultivation. The rhizome runs far underground and one season is enough to cover the surroundings. Keep it potted and standing on a saucer, and cut off any rhizome that escapes the pot as soon as you see it
Common problems
- Aphids You will see They settle between the new leaves and everything turns sticky What to do Wash them off with a jet of water. Use nothing on a plant whose root you will simmer
- Rust You will see Reddish-brown powdery spots settle on the leaves What to do Cut and remove affected leaves and open the spacing for airflow
- Chafer grubs You will see Leaves yellow and wilt, and the clump lifts easily when pulled What to do Turn the soil, pick them out and replace the potting soil
This page describes how a crop is grown and used. It does not claim health effects for any food, nor is it intended to prevent or treat disease. Component and study notes are references only and do not mean the same result occurs in people. Consult a medical professional about health concerns.
Health Benefits
The old record — mogeun (茅根). The Donguibogam lists the plant in its Herb section as 茅根 and gives the Korean name as ttippuri. It records a cold nature, with a note that some call it cool, a sweet taste and no toxicity. This, it states, is 白茅根, and it is found everywhere. The root is dug in the sixth lunar month and dried in the sun. What an old medical text wrote differs from how it is judged today.
Compounds reported in the genus Imperata. Analyses report triterpene compounds isolated from the rhizome of Imperata. The same line of work discusses the stored sugars behind the sweetness. These are compositional analyses.
Cogon grass as a weed. Spreading fast by rhizome, cogon grass is treated as a difficult weed across many regions and appears on the United States federal noxious weed list. This concerns ecology and management.
Nutrition
- Sugars (stored in the rhizome) — the source of the faint sweetness when chewed
- Triterpenes (reported in the rhizome) — a group of compounds isolated from the genus Imperata
- Potassium (present in rhizome and leaf) — a mineral common in plants
- Dietary fibre (leaf and rhizome) — the fibre behind the tough texture
Where the sweetness comes from Chew the rhizome and a faint sweetness comes through, from the sugars stored in it. That is the taste the Donguibogam recorded as sweet. The same faint sweetness carries into a decoction.
Compounds reported in the genus Analyses report triterpene compounds isolated from the rhizome of Imperata. This entry stays with the compositional record.
The window for ppilgi The young flower spike, before it opens, is soft and faintly sweet. Once it opens and the white hairs begin to blow, it turns too tough to chew. The season for it is a short stretch of spring.
How strong to brew it Baengmogeun tea is the dried rhizome brought to the boil in water and steeped. Do not brew it strong and drink it all day in place of water; keep it weak and to a cup or two a day.
Pairings
○ Simmered with jujube — A few jujubes in the pot soften the earthy note and add sweetness. Use plenty of water and a low simmer.
○ Toasted barley or brown rice — Simmered with toasted grain it gains a nutty note and drinks more easily as a weak brew. Grain makes it spoil faster, so finish it the day it is made. Barley
○ Chilled — Simmered and cooled, it drinks well cold in summer. The faint sweetness means nothing needs to be added. Finish it the same day and refrigerate what is left.
△ Digging on levees and roadsides — Cogon grass colonises exactly the places herbicide and exhaust reach: levees, road cuttings, the ground around grave mounds. If you mean to dig the rhizome, avoid maintained road embankments and field margins, and never enter private land or a burial site without permission.
△ Confusion with silver grass and reed — Cogon grass flowers in spring and stands only knee to waist high, with a white, jointed rhizome. Silver grass flowers in autumn and stands taller than a person; common reed grows at the waterside and is larger still. Out of season, with only dry leaves left, the three are hard to separate — so dig only where you confirmed the white spring plume.
△ Drinking it instead of water — Do not drink the decoction all day in place of water. Keep it weak and to a cup or two a day, and stop if anything feels wrong. If you are on medication, speak to a clinician before adding it.
Varieties
- Cogon grass (rhizome) — The commonest species in Korean fields. Its rhizome is used as baengmogeun
- Japanese blood grass (division) — The ornamental selection whose leaf tips turn red. Grown in beds and pots
Source: Donguibogam, Herb Section 茅根 · Korea National Arboretum, Korean Plant Names Index