Ornamental grasses have become a staple in modern landscaping, prized for their texture, movement, and year-round interest. They bring a natural, airy feel to gardens, contrasting beautifully with traditional flowering plants. However, not all ornamental grasses are created equal. Some can become aggressive invaders, disrupting ecosystems and outcompeting native species. Choosing the right grasses is crucial for responsible and sustainable gardening. This article explores the ornamental grasses you should avoid planting and offers alternative options for a beautiful and ecologically sound landscape.
The Problem with Invasive Ornamental Grasses
The allure of ornamental grasses is undeniable, but their potential for invasiveness poses a serious threat to biodiversity. Many popular ornamental grasses, introduced from other regions, lack natural controls in their new environments. This allows them to spread rapidly, taking over native habitats and reducing plant diversity.
Invasive grasses disrupt natural ecosystems. They can alter soil composition, increase fire risk, and negatively impact wildlife that depends on native plants for food and shelter. The economic costs associated with managing invasive grasses are also substantial, requiring ongoing efforts to control their spread and restore damaged ecosystems.
The problem is compounded by the fact that many gardeners are unaware of the invasive potential of certain grasses. They may plant them without realizing the long-term consequences for their local environment. It is essential to educate gardeners about the risks associated with invasive ornamental grasses and promote the use of native or non-invasive alternatives.
Identifying Problematic Ornamental Grasses
Several ornamental grasses are known for their invasive tendencies and should be avoided in most garden settings. Recognizing these species is the first step in preventing their spread.
Miscanthus sinensis (Chinese Silver Grass)
Miscanthus sinensis, commonly known as Chinese silver grass, is a popular ornamental grass prized for its tall, elegant plumes and graceful arching foliage. While many cultivars of Miscanthus sinensis are considered relatively well-behaved, the species itself can be quite invasive, particularly in disturbed areas and along roadsides.
The plant’s abundant seed production and efficient dispersal mechanisms allow it to spread rapidly, forming dense thickets that outcompete native vegetation. The species has proven invasive in several areas of North America. Its persistence and ability to thrive in a variety of conditions make it difficult to eradicate once established. Be especially cautious if you live near natural areas.
Pennisetum setaceum (Fountain Grass)
Pennisetum setaceum, or fountain grass, is another widely planted ornamental grass that poses a significant invasive threat. Its attractive bottlebrush-like flower heads and drought tolerance have made it a popular choice for gardens in warm climates. However, fountain grass is highly invasive, particularly in California, Hawaii, and other Mediterranean-climate regions.
This grass spreads primarily through seeds, which are easily dispersed by wind, water, and animals. The seeds can remain viable in the soil for several years, making eradication difficult. Fountain grass forms dense stands that displace native plants, reduce biodiversity, and increase fire risk. Invasive fountain grass poses a threat to native habitats in many regions.
Cortaderia selloana (Pampas Grass)
Cortaderia selloana, commonly known as pampas grass, is a large, imposing ornamental grass that produces impressive feathery plumes. While its dramatic appearance makes it a popular choice for landscaping, pampas grass is highly invasive in many parts of the world, including California, Australia, and New Zealand.
Pampas grass is a prolific seed producer, with each plant capable of producing millions of seeds that can be dispersed over long distances by wind. The seeds germinate readily, and the plants grow quickly, forming dense stands that outcompete native vegetation. Pampas grass is known for its aggressive spread and ecological damage.
Imperata cylindrica (Japanese Blood Grass)
Imperata cylindrica, also known as Japanese blood grass or cogongrass, is a rhizomatous perennial grass prized for its striking red foliage. While some cultivars are marketed as ornamental plants, Imperata cylindrica is considered one of the world’s worst weeds. It is extremely aggressive and difficult to control.
This grass spreads rapidly through rhizomes, forming dense mats that exclude other plants. It is highly adaptable and can thrive in a wide range of soil types and environmental conditions. Imperata cylindrica is particularly problematic in disturbed areas, such as roadsides and construction sites, where it can quickly establish and spread.
Alternatives to Invasive Ornamental Grasses
Fortunately, there are many native and non-invasive ornamental grasses that can provide the same aesthetic appeal without the ecological risks. Choosing the right grasses for your region is essential for creating a sustainable and environmentally friendly garden.
Native Grasses
Native grasses are adapted to the local climate and soil conditions, making them more resilient and requiring less maintenance than non-native species. They also provide valuable habitat and food sources for native wildlife.
Some excellent native grass options include:
- Little Bluestem (Schizachyrium scoparium): A beautiful clumping grass with blue-green foliage that turns reddish-bronze in the fall.
- Switchgrass (Panicum virgatum): A versatile grass with airy flower panicles and attractive fall color.
- Prairie Dropseed (Sporobolus heterolepis): A graceful grass with delicate flower panicles and a pleasant fragrance.
Non-Invasive Ornamental Grasses
Several non-invasive ornamental grasses offer the same aesthetic appeal as invasive species without the ecological risks. These grasses are well-behaved and do not spread aggressively.
Consider these non-invasive alternatives:
- Feather Reed Grass (Calamagrostis x acutiflora ‘Karl Foerster’): A popular choice for its upright habit and feathery flower spikes.
- Blue Fescue (Festuca glauca): A low-growing grass with striking blue foliage.
- Tufted Hair Grass (Deschampsia cespitosa): A graceful grass with delicate flower panicles that shimmer in the sunlight.
Responsible Gardening Practices
In addition to choosing the right ornamental grasses, there are several responsible gardening practices that can help prevent the spread of invasive species.
- Research before you plant: Before planting any ornamental grass, research its invasive potential in your region. Consult with local nurseries, extension services, and native plant societies to determine which grasses are safe to plant.
- Choose sterile cultivars: If you choose to plant a potentially invasive species, select a sterile cultivar that does not produce viable seeds.
- Monitor your plants: Regularly monitor your ornamental grasses for signs of spread. Remove any unwanted seedlings or rhizomes promptly.
- Dispose of plant waste properly: Do not compost seed heads or rhizomes of potentially invasive grasses. Dispose of them in a sealed bag in the trash.
- Educate others: Share your knowledge about invasive ornamental grasses with other gardeners and encourage them to make responsible planting choices.
Conclusion
Ornamental grasses can add beauty and interest to gardens, but it is crucial to choose wisely and avoid planting invasive species. By selecting native or non-invasive alternatives and following responsible gardening practices, you can create a beautiful and ecologically sound landscape that supports biodiversity and protects the environment. Making informed choices ensures responsible gardening practices. Take the time to research the ornamental grasses you are considering planting and make sure they are not known to be invasive in your area. Your efforts will help protect native ecosystems and preserve the beauty of our natural landscapes for future generations.
What makes an ornamental grass “invasive” or “problematic”?
An ornamental grass is considered invasive when it spreads aggressively beyond its intended planting area, often outcompeting native plants and disrupting local ecosystems. This can happen through prolific seed production, underground rhizomes, or a combination of both. Once established, invasive grasses are difficult and costly to control or eradicate.
The problematic nature stems from the ecological and economic impacts these grasses can have. Native plant communities suffer, reducing biodiversity and impacting wildlife that depend on those plants for food and shelter. Additionally, managing invasive grasses can require significant resources, including labor, herbicides, and habitat restoration efforts.
Why are some ornamental grasses considered better choices than others for a garden?
Some ornamental grasses are considered better choices because they exhibit clump-forming habits, meaning they grow in a defined area without aggressive spreading. These non-invasive grasses provide desired aesthetic qualities without posing a threat to surrounding ecosystems. They tend to have less prolific seed production or less vigorous rhizome growth, limiting their ability to escape cultivation.
In contrast, ornamental grasses that spread rapidly via rhizomes or produce an abundance of easily dispersed seeds are more likely to become invasive. Selecting non-invasive alternatives helps gardeners enjoy the beauty and benefits of ornamental grasses while minimizing the risk of ecological damage and the need for future control efforts.
What are some examples of ornamental grasses frequently cited as invasive?
One frequently cited invasive ornamental grass is Miscanthus sinensis ‘Gracillimus’ (Maiden Grass), a popular choice for its elegant form but known to self-seed prolifically. Another is Pennisetum setaceum (Fountain Grass), particularly in warmer climates, where its seeds readily germinate and establish new populations, displacing native vegetation.
Other examples include Imperata cylindrica (Japanese Blood Grass), a highly aggressive spreader through rhizomes, and Phragmites australis (Common Reed), which, while native in some areas, can become overly dominant and outcompete other wetland plants. These grasses highlight the importance of careful selection and responsible planting practices.
How can I identify if an ornamental grass is potentially invasive before planting it?
Researching a grass’s growth habits and regional invasiveness is crucial. Consult resources like your local cooperative extension office, native plant societies, and state or federal invasive species lists. These sources often provide information on plants known to be problematic in your area.
Look for descriptions of the grass’s spreading behavior. Does it form clumps or spread via rhizomes? Does it produce an abundance of seeds? Online databases and plant identification guides can provide detailed information on a grass’s characteristics and potential for invasiveness. Consider also consulting with local nurseries about non-invasive options they recommend for your area.
What are some non-invasive alternatives to popular, but potentially invasive, ornamental grasses?
For those seeking the feathery plumes of Fountain Grass (Pennisetum setaceum), consider Purple Lovegrass (Eragrostis spectabilis). This native option provides similar visual interest with beautiful purple hues and a clumping growth habit, minimizing the risk of spreading.
If you appreciate the height and architectural form of Maiden Grass (Miscanthus sinensis), Little Bluestem (Schizachyrium scoparium) is an excellent native alternative. It offers stunning fall color and provides valuable habitat for wildlife, all while staying well-behaved in the garden.
What steps can I take to manage or remove an invasive ornamental grass from my garden?
Small infestations of rhizomatous grasses can sometimes be managed by carefully digging up the entire plant, ensuring all rhizomes are removed. This method requires persistence and careful attention to detail, as any remaining rhizomes can resprout. Be sure to dispose of the removed plant material properly, preventing it from spreading further.
Larger infestations may require a combination of mechanical removal and herbicide application. Consult with your local extension office or a certified professional for recommendations on appropriate herbicides and application techniques for your specific situation and the grass species in question. Repeat applications may be necessary to completely eradicate the invasive grass.
What is “responsible gardening” in the context of ornamental grass selection?
Responsible gardening, in the context of ornamental grass selection, means making informed choices that minimize negative impacts on the environment. This involves prioritizing native and non-invasive species, understanding the potential risks associated with certain plants, and actively preventing the spread of invasive species.
It also includes considering the long-term maintenance needs of the plants you choose and implementing sustainable gardening practices that support biodiversity and ecosystem health. By selecting plants that are well-suited to your local environment and avoiding those with a history of invasiveness, you can create a beautiful garden that benefits both you and the planet.