Cyperus rotundus is a perennial sedge considered one of the most problematic weeds in agricultural and landscaping settings. The plant’s stem is erect and triangular rising from a basal bulb.
It is easily recognizable by its dark green, glossy leaves with a prominent midrib and its upright three-angled stems with reddish-purple antenna-like pods.
Cyperus rotundus Classification
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Tracheophyta
- Subphylum: Angiospermae
- Class: Monocotyledonae
- Order: Poales
- Family: Cypersceae
- Genus: Cyperus
- Species: Cyperus rotundus
- Varieties: Cyperus rotundus var. rotundus, Cyperus rotundus var. nundatus, and Cyperus rotundus var. javanicus. Cyperus javanicus
- Common Names: Purple nutgrass, Coco grass, Red grass, Red nutsedge, Nut sedge, Purple nutsedge, and Water grass.
Nativity and Distribution
Nutsedge is native to Southern Asia, particularly India and Australia. Today it is more widespread in tropical and subtropical countries in:
- Africa
- Euroasia
- North America
- South America
Physical Characteristics
- Leaves: Linear, grass-like leaves with a prominent midrib.
- Fruits: Dark brown or black 3-angled achene.
- Stems: Erect, triangular in cross-section.
- Flowers: Slightly flattened reddish-purple to reddish-brown spikelets.
- Roots: Fibrous root system.
Cyperus rotundus is a perennial sedge that grows up to 60 cm tall. It is easily recognizable by its dark green glossy leaves with a prominent midrib and its upright three-angled stems with reddish-purple antenna-like pods.
The stem is erect, smooth, and 3-sided, rising from a tuber or basal bulb. Emerging from the shoot base in ranks of threes, are dark-green, linear, slightly wavy or folded leaves with a scabrid margin about 2-6mm wide and 20cm long.
Nut grass produces linear-lanceolate, slightly flattened, reddish-purple to reddish-brown clusters of flowers 2mm wide and 1-2 cm long at the tips of the stems. Unequal rays about 2-6 cm long support the flowers. Flowering occurs 3-8 weeks after emergence which falls between late spring to summer.
The seed is small, ellipsoid to oval, about 2mm long and dark brown to black in color.
Reproduction, Dispersal, and Life Cycle
- Life Cycle: Perennial.
- Seeds: Rarely produce viable seeds.
- Climate: Tropical and subtropical climates.
- Dispersal: Water and contaminated agricultural equipment.
Cyperus rotundus behaves as a perennial and mainly reproduces by seeds, tubers, and rhizomes. While the sedge produces seeds, they generally have a low germination rate of 1-5% and therefore not considered viable or important. However, they can remain dormant for many years.
Java grass is primarily reproduced by tubers and rhizomes found at the base of the plant. The repetitive cycle of growth from the tuber, shoots, roots, and rhizomes creates a large underground network.
When the stems are pulled out, the broken parts form new roots and shoots, contributing to its highly invasive nature. The systems of renewed growth and extended seed and rhizome dormancy abilities give the plant advantageous traits that help it propagate and survive in diverse environments. Cultivation can also cause vigorous growth.
Similar Plants
- Cyperus esculentus
- Cyperus longus
- Cyperus serotinus
Uses
- The tubers are used as traditional medicine in India and China to treat digestive respiratory issues and skin ailments.
- It is used by pharmaceutical companies to make treatments for respiratory problems like coughs and asthma.
- Its extensive root system is used for soil stabilization and erosion control.
- The tubers are consumed as vegetables in some cultures.
- Dried grass is used to make sleeping mats.
Impact on Farms and Environment
While Nutsedge can provide benefits like soil stabilization and erosion control, its invasive attributes far outweigh its usefulness.
The plant is considered a serious weed in over 70 countries globally. It affects over 52 crops, including maize, phaseolus bean, barley, mustard, and cotton, reducing quantity and quality of yield.
Cyperus rotundus affects crops by competing for vital nutrients and altering the soil structure through its dense network of tubers and roots. It has also been found to have irreversible allelopathic properties on crops like cotton, barley, cocoa, tomato, orange, rice, and mustard.
Crop losses can range between 6%-90% depending on how long it is left unremoved in crop farms. Apart from the direct impact on crops, it can also interfere with the harvesting of plants like groundnuts.
Overall, nut grass infestations often increase weed control costs due to its high mobility, prolific reproduction, fast growth, and difficulty in removing the roots and tubers.
Its ability to adapt to diverse conditions and colonize rapidly also negatively affects the environment, smothering native plants and negatively impacting biodiversity. Nutsedge is commonly found in pastures, riverbanks, road and rail sides, fallow land, waste areas, and irrigation channels.
Control
- Mechanical control: Cultivation, mulching, cover cropping and rotation, and soil solarization.
- Chemical control: Herbicides like imazapic, imazapyr, 2,4-D, diclosulam, and glyphosate.
- Biological control: Fungi like balansia, puccinia, and curvularia and arthropods like athesapeuta cyperi, bactra minima, and chaetococcus australis.
The best way to control cyperus rotundus is to eliminate it as soon as it’s discovered. Sustained crop cultivation will expose the tubers to desiccation, preventing re-establishment.
Other methods such as mulching, soil solarization, cover cropping and rotation, and planting at optimal density can help provide strong competition against nutsedge at critical stages, curtailing its growth. However, these methods are often time-consuming and costly.
Chemical herbicides can provide better control against the invasive weed. Pre-emergence herbicides like carbamate products are used in maize plantations to limit its growth. Other pre-emergence herbicides that have been found effective include terbacil and bromacil.
Post-emergence herbicides like 2,4-D, amitrole, glyphosate, and other herbicides can also be used to control nutsedge. Glyphosate, in particular, has been shown to provide the best results compared to other herbicides. Multiple applications at the flowering stage can reduce tuber population by over 95%.
Kindly consult a professional for more information on the best herbicide for your crop farm or landscape.
Several promising biological agents have been released to control C. rotundus including fungi like balansia, curvularia, and dactylaria higginsii. Natural enemies including arthropods like athesapeuta cyperi, bactra minima, and chaetococcus australis have shown promising potential for effective nutsedge control.
Lead Editor for Insight Weeds.