Imperata cylindrica, a colonizer with blood-red blades… of grass!

Native and invasive range of Imperata cylindrica

While colonization among people is often subject to debate, regarding plants it can sometimes be dramatic. When Imperata cylindrica spreads outside of its native range, it turns invasive and disturbs entire ecosystems.

Check whether you should refrain from planting it in your area.

Native and invasive range of Imperata cylindrica

Native to – SouthEast Asia

Invasive in – Rest of Asia, Oceania, Africa, America (North, Central and South), Europe

Where does cogon “Bloodgrass” come from?

Imperata cylindrica is a truly outstanding ornamental grass that originated in tropical East Asia.

Several cultivars exist which aren’t very invasive, such as the ‘Red Baron’ bloodgrass. However, such cultivars are never perfectly stable. Sometimes they revert to the original, aggressive form. When this happens, it becomes difficult to control cogon grass’s spread.

Today, a vast number of states and countries around the world include this type of grass on their “Top invasives” lists.

Map of the world where Imperata cylindrica is native or invasive

Native range – Thailand, Philippines, Japan, portions of East China. Some strands are native to East Africa, as well.

Invasive range – A great many countries officially list “bloodgrass” as an invasive plant:

  • Southern and Eastern Europe – Albania, Armenia, Croatia, Cyprus, France, Greece, Portugal, Slovenia
  • Asia – Afghanistan, Azerbaijan, Bhutan, Cambodia, Sri Lanka, Turkey, Turkmenistan, Russian Federation, Kyrgyzstan, Uzbekistan, Laos, Myanmar, Nepal, India, Pakistan
  • Africa – Algeria, Benin, Burkina Faso, Burundi, Seychelles, Senegal, Sierra Leone, South Africa, Swaziland, , Cameroon, Congo (both), Ivory Coast, Egypt, Ethiopia, Togo, Tunisia, Malawi, Mayotte, Mauritius, Morocco, Mozambique, Namibia, Nigeria, Kenya, Rwanda, Mali, Lebanon, Lesotho, Liberia, Libya, Uganda, Zambia, Zimbabwe, Gabon, Gambia, Ghana, Guinea
  • Middle East – Syrian Arab Republic, Saudi Arabia, Oman, Yemen, Israel, Iran, Islamic Republic Of, Iraq, Jordan, Armenia, Georgia
  • North America – United States
  • South America – Argentina, Bolivia, Chile, Colombia, Uruguay, Peru, Venezuela
  • Oceania – Australia, American Samoa, Tanzania, Solomon Islands, Christmas Island, Tonga, Micronesia, Philippines, Samoa, Malaysia, New Caledonia, New Zealand, Indonesia, Palau, Fiji, Northern Mariana Islands, Vanuatu, Guam

Even in countries where it’s native, governments sometimes declare it a pest or a noxious weed.

Map of native range of Imperata cylindrica

Map of the world with imperata cylindrica native areas in green, around the Philippines and in Asia

Reporting Cogon bloodgrass in the United States

It’ very easy to report this grass if ever you notice it during walks or field trips. For the USA, simply head over to the EDDMapS website, create a login, and report the grass. Thanks to people like you who do it, they can create the map below, accurate down to county level. It helps local environment agencies set their priorities straight.

Regulations regarding Imperata cylindrica

In the United States, several states have legislated against sale, growing, and transporting cogongrass. Usually this pertains to the live forms (rhizomes and seeds).

The map below shows which states have taken legal action to contain the I. cylindrica cogon grass:

Learn more about invasive bloodgrass

Planting imperata cylindrica in potsInterestingly, almost all invasive cogon grass in the United States can be traced back to a meager 4 individual plants! A genetic analysis revealed that the genetic diversity was minimal. Four patches of grass now endanger the entire environment of the American South-East!

Accordingly, the first were a few rootlets that fell out of an orange crate delivered from abroad to Alabama. Then, since the plant seemed to be a promising grower, it was introduced with the idea of providing fodder for cattle. By the time they realized cows hated eating the razor-sharp blades, it was too late. Controlling invasives back then didn’t have the importance it has now.

Controlling cogongrass

Very difficult, due to the extensive root system.

  • Burning won’t eliminate the plant. Usually, it even triggers blooming!
  • Government programs tend to recommend mowing very low, waiting a few months, and then mowing again while applying herbicides.

Smart tip about cogon grass

A brilliant way to still grow these plants is to plant them in pots. That way, they won’t spread through their root system. Normally, varieties like the Imperata cylindrica ‘Red Baron’ don’t go to seed easily. They aren’t as dangerous as the original cogongrass lineages.

Sources (maps and research)GSID, as of December 18th, 2020
Institute for Plant Genomics and Biotechnology, Department of Horticultural Sciences, Texas A&M University

Credits for images shared to Nature & Garden (all edits by Gaspard Lorthiois):
Just grass, but so invasive! by Rob Bakker under Public Domain
Great way to control it by Daryl Mitchell under © CC BY-SA 2.0
World Map base by Smurfy under © CC BY-SA 3.0