Pampas grass (Cortaderia spp.) is a large, perennial ornamental grass native to South America, instantly recognizable by its towering, feathery plumes. Its dramatic height and texture made it a popular choice in landscaping globally. However, this appealing plant frequently escapes cultivation to colonize natural areas. The central question for homeowners and land managers is whether this attractive feature poses an invasive threat to local ecosystems.
Defining Its Invasive Status
The invasive status of pampas grass depends on the specific species planted and the local environment. There are two primary species of concern: the common ornamental pampas grass (Cortaderia selloana) and the highly aggressive jubatagrass (Cortaderia jubata). C. jubata is the more problematic species, especially in areas like the US West Coast and New Zealand, often listed as a legally restricted noxious weed.
This distinction is important because the two species spread differently. C. selloana is sexually reproducing (dioecious), requiring both male and female plants for viable seeds. In contrast, C. jubata reproduces asexually through apomixis. This means female plants can create thousands of viable seeds identical to the parent without cross-pollination, allowing C. jubata to establish and spread rapidly.
Environmental Impact and Spread Mechanisms
Once established in wild areas, pampas grass fundamentally alters the landscape through prolific seed production and a clumping growth habit. A single mature plant can produce millions of wind-dispersed seeds annually, with each plume containing up to 100,000 seeds. These lightweight seeds travel long distances on the wind, quickly colonizing disturbed ground, roadsides, and cliff faces.
The dense, tightly packed clumps effectively crowd out native, low-growing vegetation. This aggressive competition for light, water, and nutrients reduces species richness and lowers the overall biodiversity of the habitat. The sheer size and density of the tussocks can also make habitats unusable for native wildlife seeking shelter and food.
Pampas grass also creates a significant fire hazard due to the large volume of dead, dry material that accumulates at the base. This material is highly flammable and acts as a potent fuel source, often referred to as “ladder fuel.” When ignited, these dense clumps burn intensely, increasing the heat and spread rate of wildfires.
Practical Control and Removal Methods
Removing an established pampas grass clump requires a combination of physical labor and targeted chemical treatment due to the plant’s massive root crown.
Physical Removal
The first step involves cutting the sharp-edged foliage down to a few inches above the ground, using heavy protective gear. It is important to carefully bag or cover any plumes before cutting to prevent accidental seed dispersal. Once the foliage is removed, the entire root crown (rhizome) must be physically dug out. Leaving behind fragments of the dense root system can result in resprouting, often necessitating repeated manual removal or the use of heavy machinery.
Chemical Control
For chemical control, a targeted application of a systemic herbicide, such as glyphosate, directly to the freshly cut stems can be effective. Chemical application is most successful when the plant is actively growing and before it sets seed, allowing the herbicide to be efficiently translocated to the deep root system. Multiple treatments may be required for large or older plants. Proper disposal of all plant material is necessary; cut plumes and debris should be securely bagged and taken to a waste facility.
Safe Alternatives for Landscaping
Homeowners wishing to capture the dramatic appeal of pampas grass without the environmental risk have several excellent, non-invasive ornamental alternatives. These options provide similar height, texture, or the feathery plume aesthetic:
- Giant Wildrye (Elymus condensatus) is a native option in some regions, providing towering height and texture.
- Switchgrass (Panicum virgatum), particularly taller cultivars, offers upright structure and seasonal interest with airy seed heads.
- Feather Reed Grass (Calamagrostis x acutiflora ‘Karl Foerster’) maintains a vertical, non-spreading habit.
- Deer Grass (Muhlenbergia rigens) and Pink Muhly Grass (Muhlenbergia capillaris) provide beautiful, fine-textured foliage and plumes.
These alternatives offer the desired visual impact while supporting local ecosystems and preventing the spread of invasive seeds.