The red form of Imperata cylindrica (usually called Japanese Blood Grass here in the USA) is my favorite ornamental.
But what some people might not know is that this species has a dark side too. It also exists as a wild, non-ornamental form that is considered one of the top 10 invasive plants in the world, Cogongrass.
|Wild cogongrass (c) Keisotyo from Wikipedia|
The ornamental form is smaller, mostly sterile, and is much slower growing than the wild form. It also has attractive red leaves that make it a prized specimen among ornamental grass aficionados.
Unfortunately, under certain conditions, this ornamental form can revert back to the wild form or produce seeds, and so Japanese Blood Grass cannot be sold, traded, or grown in quite a few states.
|Comparison of greenhouse grown Imperata cylindrica var. koenigii (Japanese blood grass), Reverted I. cylindrica var. koenigii (JBG Revert) and I. cylindrica (Wild-type cogongrass). (c) Cseke, L. J., Talley, S. M. A|
If you are in a growing zone where there is no chance of the ornamental form reverting to the wild state, then this species can be a striking addition to your collection or garden.