Black Fountaingrass

What’s this fuzzy-looking flowerhead? Black fountaingrass (Cenchrus purpurascens) is an invasive plant that is also a popular ornamental grass due to its red-to-purple-colored flowerhead. It can be found in plazas and housing complexes throughout the greater Washington, DC area that we call the National Capital Region (NCR).

Black fountaingrass spreads quickly. Bristles that stick outward and whorl around the seed, making it easy to attach to fur, clothes, and shoes, and adhere to passersby. They can also spread by birds, wind, water, and mowing.

While black fountaingrass was initially thought to be an Early Detection and Rapid Response species, the NCR Invasive Plant Management Team (IPMT) quickly realized how well-established the grass is throughout NCR. In autumn of 2023, large infestations of black fountaingrass were reported, especially along C&O Canal and Rock Creek. IPMT focused their efforts on monitoring black fountaingrass throughout NCR parks and reducing seed production using herbicide treatment. Volunteers also helped by surveying along Rock Creek and cutting off flowerheads. During the 2024 field season, IPMT has seen great improvements in where black fountaingrass was previously treated.

How to Identify Black Fountaingrass

Black fountaingrass is a perennial grass. The bristles on the flowerhead can range from green to purple from summer through early fall (Brookman, 2015; Flora of China n.d.). Like most grasses, black fountaingrass is most easily identified when in flower or seed.

Characteristics to look out for:

• Clumpy and grows up to 3 feet tall
• Leaves are flattened along the stem and branch out, forming a shap similar to an elongated fan
• Smooth, white line and hairs are present where leaf blade meets the stem
• Resistence when gliding fingers from leaf tip toward the stem
• Hairy flowerhead stem
• Generally found along waterways, wet to moist soils, and floodplains, but can also be found in dry lawns around the region

Look-alikes

**Native bottlebrush grass (Elymus Hystrix) **

Native Bottlebrush grass. Two views of flowerhead featuring two spikelets in opposite arrangement. Left: mefisher (CC0). Right: Jim Bowhay (CC0); iNaturalist.

The native bottlebrush grass (Elymus hystrix) is another grass with a similar flowerhead to black fountaingrass. Here are some ways to tell the differences between the two:

Several native grasses in our region have this bottlebrush flowerhead, but none of them have the purple color that black fountaingrass has. This makes the non-native grass distinct during the flowering period.

Tips for making a good observation record of black fountaingrass

Take photographs that show:

• Area where they were found
• Infestation/population
• Numerous photos of the whole plant that include the flowerhead
• If flowerheads not present, then provide a closeup of the flattened leaves

Make comments that:

• Explain whether the plants are intentional or wild
• Give a rough estimate of the number of plants and the area covered

References

Brookman, Susan. 2015. Pennisetum alopecuroides/NJ. Retrieved 8/16/23 from https://wiki.bugwood.org/Pennisetum_alopecuroides/NJ \

Flora of China. n.d. Pennisetum alopecuroides. Retrieved 9/10/24 from [efloras.org/ florataxon.aspx?flora_id=2&taxon_id=200025851 ](efloras.org/ florataxon.aspx?flora_id=2&taxon_id=200025851)

Lee, M.T. 2023. Cenchrus purpurascens. Flora of Southeastern United States by North Carolina Botanical Garden. Retrieved 8/16/23 from https://fsus.ncbg.unc.edu/show-taxon-detail.php?taxonid=2232

NCU Extension. n.d. Cenchrus alopecuroides. Retrieved 8/16/23 from https://plants.ces.ncsu.edu/plants/cenchrus-alopecuroides/

NCU Extension. n.d. Elymus hystrix. Retrieved 8/16/23 from https://plants.ces.ncsu.edu/plants/elymus-hystrix/

Where this belongs

• Chesapeake & Ohio Canal National Historical Park
• Great Falls Park
• George Washington Memorial Parkway
• National Capital Parks-East
• Piscataway Park
• Prince William Forest Park

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