Nutgrass is a common name for nutsedge, a perennial weed considered one of the world’s most aggressive and difficult to eliminate from lawns and gardens. This plant is a formidable competitor, capable of quickly taking over manicured turf and flowerbeds due to its rapid growth and tenacious underground network. The challenge lies not just in killing the visible shoots but in eradicating the subterranean structures that allow it to survive for years.
Defining and Identifying Nutgrass
Despite its common name, nutgrass is not a true grass but a member of the sedge family, Cyperaceae. This distinction is important because it means the plant is unaffected by many common grass-selective herbicides. The two most widespread and problematic species are yellow nutsedge, scientifically known as Cyperus esculentus, and purple nutsedge, Cyperus rotundus.
The most reliable way to distinguish nutgrass from desirable turf is by examining its stem just above the ground. True grasses have round, hollow stems, but all sedges, including nutgrass, possess a solid stem with a distinctive triangular cross-section. This feature gives rise to the old saying, “sedges have edges.”
Beyond the stem structure, visual cues help differentiate the two main species. Yellow nutsedge typically has lighter, yellow-green foliage with pointed leaf tips and produces tubers singly at the end of its rhizomes. Purple nutsedge, conversely, displays darker green leaves with more rounded tips and forms its tubers in distinctive underground chains. Both varieties grow noticeably faster and taller than surrounding turf, especially in the heat of summer, making them easy to spot in a lawn.
The Mechanics of Nutgrass Reproduction
The primary reason nutgrass is so challenging to eradicate lies in its extensive, energy-rich underground reproductive system, consisting of tubers and rhizomes. The tubers, often called nutlets, are small, starchy storage organs that anchor the plant and allow it to survive harsh conditions, such as drought and winter freezes. These tubers fuel the plant’s aggressive growth and are the main source of re-infestation.
A single nutgrass plant can rapidly colonize a large area by producing hundreds, or even thousands, of new tubers and rhizomes in a single growing season. For instance, one purple nutsedge tuber has the potential to generate nearly 100 new tubers within 90 days under favorable conditions. The rhizomes, which are underground stems, spread laterally, sometimes forming dense mats that can span three to six feet across in one year.
Crucially, these tubers possess a natural dormancy that protects them from control efforts. They can remain viable in the soil for seven to ten years, meaning that even if the visible plant is killed, dormant tubers deep in the soil can sprout later. This protective mechanism ensures continuous re-emergence, requiring control methods to successfully address this underground reserve for long-term success.
Control Strategies for Removal
Because of the plant’s robust underground structure, control requires a combination of mechanical, cultural, and chemical strategies. Simple hand-pulling or mowing is largely ineffective and often counterproductive. Pulling the visible shoot typically leaves the tubers intact, which can stimulate the remaining dormant tubers to sprout new shoots, effectively increasing the infestation.
For small, isolated patches, mechanical removal must involve carefully digging out the entire plant, ensuring all attached tubers and rhizomes are removed from the soil. This process is labor-intensive and requires diligence, as any remaining nutlet can regenerate a new colony. The disturbed soil must be monitored closely for new sprouts to deplete the underground tuber supply.
Cultural practices are important preventative measures, as nutgrass often thrives in disturbed, thin turf or areas with poor drainage. Improving soil drainage and reducing overwatering can make the environment less hospitable to the weed. Maintaining a healthy, dense lawn by setting the mower to a higher cutting height encourages the turf to shade the soil, reducing the light needed for nutgrass to germinate and grow.
When chemical control is necessary for larger infestations, specialized herbicides are required because standard broadleaf weed killers do not affect sedges. Look for products containing active ingredients like halosulfuron or sulfentrazone, which are specifically formulated to be absorbed by the leaves and translocated down into the tubers. Timing is important, with applications being most effective in the early summer when the plants are actively growing but have not yet developed extensive, mature tuber chains. Multiple applications spaced several weeks apart are necessary to ensure the herbicide reaches and exhausts the entire underground network.