Avoid Planting These 11 Invasive Ornamental Grasses

When certain grasses grow outside of their native range, some can spread unchecked. A plant becomes invasive when it outcompetes local native species, yet many people unknowingly plant invasive ornamental grasses in their landscape.

The most aggressive invasive grasses spread by rhizomes that can sprout and spread even after the leaves are pulled. This makes them difficult to contain, and they can spread to areas of your garden where you might not want them. If you want to avoid the backbreaking work of digging up invasive rhizomes, avoid these 11 popular ornamental grasses that are considered to be invasive in most of the United States.

Native vs. Invasive Ornamental Grass

There are many benefits of adding aesthetic grassy plants to your landscape. Most ornamental grasses are tough, drought-tolerant, perennial, and low-maintenance. They are beautiful, lush, and green in the summer. Some even produce interesting seed heads that will remain standing over winter.

They will turn a beautiful auburn and then brown but still add a pop of texture during the cold winter months, when not much else is adding visual appeal to the garden. They also sway in the wind, provide shade to smaller plants, and shelter wildlife.

However, invasive rhizomes can rapidly spread through your landscape and “escape” to neighboring ecosystems. It’s important to consider native grasses and avoid invasive species when planning your landscaping. Native plants grow naturally in your local area and are well-adapted to the local conditions. Invasive grasses come from abroad and are often sold as landscaping plants without warnings about their aggressive spread.

Native ornamental grasses have all of the same benefits without the drawbacks of invasive ornamentals. They grow with little to no maintenance or irrigation. Their seed heads feed local wildlife, and they don’t spread and choke out other native plants. They are easy to control and still add beauty to your garden year-round.

Below are some species you should avoid planting:

Pampas Grass

Cortaderia selloana, or Pampas Grass, is named after the Pampas region in South America from where it originated. Cortaderia is derived from the Argentine Spanish name ‘cortadera’, meaning ‘cutter’, which refers to its razor-sharp leaf margins. This sharp foliage makes it physically difficult to remove this plant once it has been established. It is recommended to wear long sleeves, long pants, gloves, and eye protection when digging it up or pruning it. 

Pampas Grass is often used as an ornamental because it is a fast grower and can reach heights of up to 10 feet very quickly. It produces pretty feathery white or pinkish plumes atop the stems. Hardy in USDA growing zones 7-11, this plant is easily invasive in areas with mild winters, especially the Southern United States. It has been outright banned in Hawaii and New Zealand because of its ability to displace native species. 

If you absolutely adore the aesthetic form of Pampas Grass, consider a non-invasive seedless cultivar like ‘Sterile Dwarf Pampas Grass.’ However, there is still discussion about whether or not sterile cultivars may or may not damage local ecosystems.

Lilyturf

Lilyturf is also commonly known as monkey grass and grows as a dense ground cover. There are several species, and it’s important to know which one you’re planting to avoid the invasive types. Liriope spicata is considered invasive because it rapidly spreads via runners and rhizomes. Once planted, it can be difficult to control and is labeled as invasive in parts of the Southeastern United States. 

L. muscari, is another clump-forming grass that is hard to control, with the same low-growing ground cover habit. It is hardy in USDA growing zones 5 to 10. It produces purple-violet flowers in the late summer that eventually turning into berries. If you leave it to flower, it will take over. 

Japanese Silver Grass

Miscanthus sinensis, or Japanese silver grass, is also known as Chinese Silver Grass or Maiden Grass. It comes from Eastern Asia and grows wild in China, Japan, Taiwan, and Korea. Japanese Silver Grass thrives in full sun and can grow to be up to 12 feet tall and five feet wide. It grows in USDA growing zones 4-9. 

The attractive feathery pink or silver flowers appear in late summer. This invasive grass forms dense clumps that spread out via underground runners, and the flowers produce light, fluffy seeds that spread easily on the wind. There are sterile varieties, however, that produce little to no seeds. But you will still have to contend with aggressive rhizome spread. For these reasons, Japanese Silver Grass is an invasive plant in parts of North America, mainly the South.

Fountain Grass

Cenchrus setaceus, or Fountain Grass, is also called Crimson Fountain Grass. It is a perennial clump-former native to East Africa, the Middle East, and Southwestern Asia. Fountain Grass thrives in dry, warm areas without irrigation, making it easy for this plant to invade native species.

In 2017, Fountain Grass was added to the Invasive Alien Species of Union Concern List, which means it can’t be imported, cultivated, commercialized, planted, or intentionally released into the wild in the European Union. It is also listed as “moderately invasive” on the California Invasive Plant Inventory, as well as in other states.

Fountain Grass grows two to four feet tall and forms purple, pink, or green flowers. The flowers produce seed heads, and while some varieties claim to be sterile, they can still produce small amounts of viable seeds that can spread. Fountain Grass grows thickly and easily outcompetes and overcrowds other native plants. When these thick stands die back and dry out in the winter, they also become fuel for wildfires. 

Common Reed

Phragmites australis, a type of common reed, is non-native in North America. Many reed species to native to North America. However, this non-native variety has escaped into the natural ecosystem and can now be found all across the United States. It has quickly spread across marshes and other wetland areas. 

In its ideal habitat, Phragmites australis will drive out native plant species with their sheer height and density, which deprives surrounding plants of light and nutrients. They also deny fish and wildlife space and nutrients, blocking access to the water for fishing and swimming. In dry regions, the stalks and feather seedheads pose a fire hazard. If you’re looking for a reed to plant along your pond or other water features, be sure to choose a native species. 

Smooth Brome

Bromus inermis, or smooth brome, is endemic to Europe. Immigrants originally brought it to North America in the 1800s as a feed source for horses and cattle. This thick, mat-forming perennial is tough and drought-tolerant, which seems perfect when you need reliable fodder for livestock. However, this deeply rooted grass quickly forms a monoculture. It outcompetes native plants and wildflowers over time. 

Due to the qualities mentioned above, smooth brome is a common sod or turf grass in North America. When grown in a lawn and subject to constant mowing, it will not get the chance to produce seed heads and is less likely to spread. If you don’t want to remove this invasive grass, be sure to keep it neatly mowed. This will not eliminate the issue, though.

Reed Canary Grass

Phalaris arundinacea, or reed canary grass, is a tall perennial that prefers wetlands. It is endemic to parts of Europe, Asia, and Africa. This perennial spreads and can be hard to eradicate due to thick forming underground rhizomes. Quite a few cultivars of P. arundinacea are used as ornamentals. They are variegated or striped and sometimes called Ribbon Grass. 

This grass is used for hay or cattle forage, and its fibers are valuable for papermaking. It can be compressed it into bricks or pellets for prospective use as an alternative biomass. This grass, however, quickly outcompetes native species, especially in its ideal growing conditions of wetlands and riverside meadows. Because of its aggressive spreading habit via underground rhizomes and seeds, it’s best not to plant it in the home garden. 

Johnson Grass 

Sorghum halepense, or Johnson grass, is native to parts of Asia and Africa. It has been introduced to all continents except for Antarctica. Like Smooth Brome, it was originally brought to North America as a source of forage for cattle. Today, it is a common lawn or turf grass.

Like many other invasive grasses, Johnson Grass is difficult to remove or contain once it’s established. This is because of the aggressive underground rhizomes it produces. It grows and spreads rapidly, choking out surrounding native plants. This invasive ornamental remains problematic even when used as a mowed lawn replacement. It is also resistant to many herbicides, including glyphosate, which makes it even more difficult to contain.

Mexican Feather Grass

Nassella tenuissima, or Mexican Feather Grass is native to Mexico and the Southwestern United States. Though it is native to some parts of North America, it is on California’s list of invasive plants. It is becoming naturalized in the San Francisco area. In Australia, it is illegal to import N. tenuissima because of its risk to the native Eucalyptus woodlands.

It produces tall, feathery seed heads that sway hypnotically in the wind. It provides a stunning accent for the ornamental garden. However, Mexican Feather Grass can produce up to 10,000 seeds per plant. These seeds easily disperse in the wind, making it difficult to control. Once it escapes, it will crowd out native plants and spread into urban and agricultural areas alike. Unless you live in its native range in Texas, New Mexico, and Mexico, avoid planting this one.

Marram Grass

Ammophila arenaria, or Marram Grass, is also known as European Beach Grass. It is native to the coastlines of Europe and North Africa. This perennial forms stiff, upright clumps that grow up to four feet tall. Underground rhizomes spread up to six feet laterally in as little as six months. One clump can produce up to 100 new shoots annually. Additionally, the rhizomes can tolerate seawater. They will often break off from the main plant and float in the water until they reach land where they can once again sprout and become established.

Marram Grass is considered a noxious weed in coastal California. Biologists originally introduced it to North America because it tolerates sand and salt. They thought it could help stabilize shifting sand dunes.

Unfortunately, this invasive ornamental grass spreads rapidly and now grows along the coast from California to British Columbia. It continues to overcrowd and outcompete native plants. If you’re looking for an ornamental grass that will tolerate coastal conditions and sandy soil, then please consider California Red Fescue, which is native to that area. 

Bamboo

Bamboo is a flowering evergreen perennial that is a part of the subfamily Bambusoideae of the grass family Poaceae. Bamboo is one of the fastest-growing plants on earth, and some varieties grow as much as three feet in 24 hours! It’s no surprise that these fast-growing properties also make some varieties of bamboo invasive.

Bamboo may look attractive when grown in a small container or a pot, but when planted directly in the ground, it can certainly become invasive. There are two main types of bamboo: “clumping” and “running.” The clumping varieties spread slowly compared to the running varieties which spread aggressively via underground rhizomes. 

Some varieties of bamboo send out runners that can spread 10 feet in a single year. As a result, landscapers often dig a trench and fill it with concrete or metal barriers to contain bamboo runners. But this doesn’t always work. When not properly controlled, bamboo can quickly spread into adjacent areas. If you want to grow bamboo, it’s best to choose a clumping type and grow it in a pot or container. 

There are some species of bamboo that are native to various regions of the US. If you are interested in planting your own bamboo, look for one that is native to your local ecosystem. If there isn’t one, avoid planting.