If you’ve been rearranging your yard, you might be considering adding ornamental grasses. These low-maintenance plants are famous for bringing interesting textures and colors to a garden. However, when selecting a variety for your property, be very careful to avoid invasive grasses.
Invasive grass species may have arrived in North America through contaminated seeds or intentional or accidental planting due to lack of awareness. Whatever their origin, these pests are fierce competitors for native plants, rapidly taking over and often tolerating climate extremes.
Cheatgrass, for example, re-establishes itself quickly after a wildfire. Invasive grasses’ seeds disperse on animals’ bodies or via the wind or waterways. Alternatively, the invaders may spread through underground rhizomes.
- Ornamental Grasses that Take Over Yards
- What Problems Do Invasive Grasses Cause?
- How to Control Invasive Grasses
- Fountain Grass (Pennisetum setaceum)
- Common Mediterranean Grass (Schismus barbatus)
- Giant Reed (Arundo Donax) – Enormous Invasive Grasses
- Medusahead (Taeniatherum caput-medusae)
- Chinese Silvergrass (Miscanthus sinensis)
- Cheatgrass (Bromus tectorum)
- Buffelgrass (Cenchrus ciliaris) – Resilient Invasive Grasses
- Brome Grass (Bromus inermis)
- Japanese Stiltgrass (Microstegium vimineum) – Flexible Invasive Grasses
- Cogongrass (Imperata cylindrica)
- Common Reed (Phragmites australis)
- Reed Canary Grass (Phalaris arundinacea) – Deceptive Invasive Grasses
- Johnsongrass (Sorghum halepense)
- Burma Reed (Neyraudia reynaudiana)
Ornamental Grasses that Take Over Yards
To avoid contributing to the problem, make sure only to plant native plants, such as switchgrass or prairie dropseed, and not any of the types that we mention here.
If you’re not sure which species are suitable for your area, check with your local nursery or garden center. Be wary of self-seeding grasses and creeping grasses, which have long rhizomes and stems that grow independently of each other.
What Problems Do Invasive Grasses Cause?
Invasive species often crowd out native species, in terms of both space and available resources. Invasive plants thrive in wide-ranging conditions and often spread more quickly than native plants.
Furthermore, a 2016 study from the University of Massachusetts Amherst and the University of Colorado-Boulder, led by Emily Fusco, found that eight kinds of invasive grasses in the United States exacerbate the danger of wildfires.
These species, in combination with factors like climate change, increase blazes’ likelihood and severity.
How to Control Invasive Grasses
There are diverse ways to try to limit invasive grasses. The best method depends on the species, but often an integrated strategy is the most successful.
Physical methods like mowing, yanking, and animal grazing can be useful, and even prescribed burns in certain circumstances. Although chemical herbicides are often an option, improving native species’ resilience and health is a more sustainable approach.
Fountain Grass (Pennisetum setaceum)
This invasive grass grows in large clusters of narrow leaves that end in elegant plumes. It’s native to North Africa but causes problems in the southwestern United States, most notably California, sprouting at roadsides and on hills and rocky outcrops.
Fountain grass seeds spread by wind and water. It tolerates varied conditions but prefers fertile, well-drained soil and full sun.
This invader increases wildfires’ incidence and intensity, then colonizes rapidly after a fire, preventing other plants from putting down roots. Even without fire’s help, fountain grass easily dominates native plants.
Common Mediterranean Grass (Schismus barbatus)
This invasive annual’s small tufts tend to emerge in gaps between shrubs. It likes the desert but also pops up in bare or disturbed soil in coastal regions. Its dustlike seeds spread on the wind and in floods.
Once settled, common Mediterranean grass grows abundantly, developing a thick underground root mat and reducing nutrients’ availability for other species. Its straw-colored dried stems remain in place for up to two years after a plant’s death, enabling fire to spread.
Giant Reed (Arundo Donax) – Enormous Invasive Grasses
The leaves of this invasive reed grow at the astonishing rate of four feet per day, up to a maximum height of 25 feet. It’s native to East Asia, but people plant it around the world. This reed tolerates varied conditions, from rivers to saline soil.
Giant reed’s dense clusters displace native plants and act as fuel for flames. This plant also uses much more water than native species do. It reproduces through spreading plant fragments or underground rhizomes.
Medusahead (Taeniatherum caput-medusae)
When this slender annual dries out, its leaves turn light gray or tan and start to twist like the snakes on the ancient Greek monster. It spreads its seeds with the help of the wind, water, and animals.
Medusahead hails from southern Europe and northern Africa. Today, it grows in several American states, including Washington and Idaho. It tends to grow in grasslands, shrublands, and oak savannas and forests.
This grass outcompetes native species and increases the risk of fire. Early in the season, medusahead is also dangerous for animals that choose to snack on it, with sharp awns that injure the inside of their mouths.
Chinese Silvergrass (Miscanthus sinensis)
This invasive grass reaches up to eight feet tall and tends to grow in clusters. Native to eastern Asia, Chinese silvergrass is causing problems in the American mid-Atlantic. Americans started planting it as an ornamental, not knowing about its aggressiveness and stubbornness, with its deeply buried rhizomes and many seeds.
For a long time, scientists thought that Chinese silvergrass only spreads via its rhizomes. However, they now know that two or more Miscanthus cultivars placed side by side can cause each other to seed.
Cheatgrass (Bromus tectorum)
This annual invasive grass grows up to two feet tall with leaves covered in soft short hairs. It produces nodding green, red, or purple flowers in May or June. Seeds typically germinate in the fall, giving the plant a chance to expand its roots over the winter.
Cheatgrass depletes soil moisture and nutrients, besides encouraging the occurrence of wildfires by drying out quickly. It replaces native vegetation in the western United States in open areas like pastures and prairies.
Buffelgrass (Cenchrus ciliaris) – Resilient Invasive Grasses
This shrubby perennial grass splits into multiple leaves and flowers. Its reddish-brown or straw-colored flowers contain small spikes or burrs that attach to animals and humans, who then disperse its seeds.
Buffelgrass has its origins in Africa, Indonesia, Asia, and the Middle East. It makes its home mostly in the southern United States, although it also tolerates the climate of more northern states.
It tends to settle in disturbed areas like roadsides, as well as on hillsides and in fields. Buffelgrass’s compactness and high drought tolerance enable it to outcompete native plants for resources and eventually crowd them out. It’s also well-adapted to fire.
Brome Grass (Bromus inermis)
This perennial grass grows to be two to three feet tall and produces leaves that are grayish blue on one side and green on the other. Farmers have planted brome grass for forage grass for livestock, but you’re as likely to find it on roadsides or riverbanks or in woods or prairies.
Brome grass develops an extensive root network and reproduces via its rhizomes. It tolerates both cold and drought and is a fierce competitor for native plants, growing so thickly that it pushes out native grasses.
Japanese Stiltgrass (Microstegium vimineum) – Flexible Invasive Grasses
With a maximum height of only three-and-a-half feet, Japanese stiltgrass looks like a small bamboo plant. It has distinctive long, narrow leaves that contain a strip of silvery hairs and an off-center midrib.
Like several other types of invasive grasses, it spreads seeds through the movement of water, soil, and animals.
Japanese stiltgrass is native to parts of Asia but is dominating native plants in the eastern United States. It lives in various habitats, including forest edges, streambeds, and fields.
Cogongrass (Imperata cylindrica)
This perennial produces bunches of light-green or orange-brown leaves that reach up to four feet long. Cogongrass’s plumes end with numerous tiny seeds, which travel great distances on the wind and animals.
However, for localized spread, scientists only know for sure that cogongrass employs its rhizomes. A native of Southeast Asia, this invader establishes itself in tropical and subtropical regions, including the southeastern United States.
It grows in areas of human disturbance, such as roadsides, parks, and mining areas. Aggressive cogongrass forms monocultures on agricultural land. Its rhizomes even release substances that inhibit other plants’ growth.
Common Reed (Phragmites australis)
At over 15 feet tall, common reed makes a striking silhouette against a river or pond. Clusters of this invasive grass often combine living and dead stems. In July and August, it produces purple or gold flowers.
This perennial grows in disturbed areas like roadsides and around wetlands and bodies of water. Although there’s at least one variety that’s native to the United States, the most significant strain in the Northeast is non-native.
Common reed develops a thick root and rhizome network, pushing out native species with its dense growth. It spreads through a combination of seeds, rhizomes, and stolons, or horizontal stems that lie on the soil surface. Common reed also increases the risk of wildfire.
Reed Canary Grass (Phalaris arundinacea) – Deceptive Invasive Grasses
This perennial reaches up to nine feet tall, with gradually tapering rough-textured blades. From May to mid-June, reed canary grass produces small purple or green flowers that eventually turn beige.
This grass likes to grow in temperate regions, in both wetlands and areas that humans have disturbed. It spreads via rhizomes and seeds, which water, humans, and other animals all disperse unintentionally.
Farmers have been planting reed canary grass as a source of forage and form of erosion control for many years. However, this grass spreads aggressively. It also develops a massive seed bank that can erupt at any time.
Johnsongrass (Sorghum halepense)
This fast-growing perennial grows as tall as seven feet. It has a large seedhead that produces seeds that remain viable for up to 20 years. Johnsongrass also spreads using fragments of its rhizomes.
Johnsongrass grows in all states except for Alaska and Minnesota. It makes itself at home in roadsides, ditches, and other disturbed soil, as well as on stream bottoms.
Johnsongrass overwhelms native plants, leading to the development of a monoculture. Even without completely wiping them out, it causes corn and soybean yields to decrease.
Burma Reed (Neyraudia reynaudiana)
This tall perennial grows in clusters of multiple stalks. It contains large plumes and leaves with one horizontal row of hairs. Its plumes all carry hundreds of flowers.
Burma reed reproduces using both seeds and rhizomes. It likes to grow anywhere that the soil has been displaced, such as the edges of roads and forests. It also establishes itself in bogs and marshes, savannahs, and upland cliffs.
Burma reed crowds out native plants and creates the ideal conditions for destructive wildfires. Its large plumes and dense litter are highly combustible.
In general, ornamental grasses make excellent additions to a yard, bringing unique textures and colors. However, we caution you to avoid planting non-native grasses.
With so many native varieties available, and the risk of invasiveness among non-native species, planting a native grass seems like the most straightforward solution.
Invasive grasses spread aggressively, dominating or pushing out other species, and even increase the risk of wildfires. They may be beautiful, but they should not grow in your garden.
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