Pampas grass (Cortaderia selloana) is a large, ornamental grass known for its striking plumes. The plant’s substantial size hints at its below-ground architecture, which is a major factor in its hardiness and ability to dominate landscapes. Understanding the depth and structure of the root system is important for anyone considering planting this species or attempting to manage an existing clump.
The Physical Structure of Pampas Grass Roots
Pampas grass anchors itself with a dense, fibrous root system that forms a massive, impenetrable root ball. This structure does not feature a single taproot but is instead a thick tangle of fine roots growing directly from the base of the plant. The root mass is concentrated beneath the crown, creating a solid foundation that resists disturbance.
In optimal conditions, the roots of a mature pampas grass clump can penetrate the soil to impressive depths, sometimes reaching up to 11 feet below the surface. This deep penetration allows the plant to access water and nutrients far beyond the reach of most other garden plants. The lateral spread of the roots is often equally substantial, extending outward to a diameter of 13 feet or more in established specimens.
While pampas grass is not a true rhizomatous grass, the dense, woody nature of its root crown and the short, stocky growth of new tillers create a similar spreading effect. This root crown becomes progressively harder and more compacted over time, making it difficult to cut through. The volume of the root system has been calculated to occupy over 100 cubic meters of soil on large, older plants.
Biological Function of the Extensive Root System
The massive root structure is an evolutionary adaptation that gives pampas grass a distinct advantage in diverse environments. The primary function of this deep system is superior resource acquisition, particularly water. By driving roots several feet down, the grass can tap into deeper water tables, allowing it to remain vigorous during prolonged periods of drought.
This deep reach gives the plant its drought tolerance, enabling it to thrive in regions with seasonally dry soils. The dense network of roots also provides exceptional stability, firmly anchoring the tall, heavy plant against high winds and preventing soil erosion. The extensive root system enhances the plant’s ability to scavenge nutrients from a vast volume of soil.
The fibrous roots allow the plant to colonize areas with poor or nutrient-depleted soil, outcompeting shallow-rooted species for limited resources. This robust root architecture is why pampas grass has historically been used for stabilizing mine dumps and tailing sites.
Managing and Removing Established Pampas Grass
Removing an established clump of pampas grass is a significant undertaking because of the root system’s depth and density. Manual removal requires effort, typically involving cutting the foliage back to the ground first to expose the root crown. Tools like a pickaxe, mattock, or sharpened shovel are necessary to chip away at the tough, woody root ball in sections.
For large clumps, heavy machinery, such as a backhoe or excavator, may be the most practical option for complete removal. It is important to extract the entire root crown, as any pieces left in the soil can potentially regenerate. The volume of the root mass means that once removed, a large void will need to be filled with topsoil.
Chemical control is an alternative strategy, which involves cutting the plant down to a few inches above the soil line and applying a targeted herbicide, such as glyphosate, directly to the exposed crown. This application is often more effective in the fall when the plant naturally translocates resources to its roots. Multiple treatments over several weeks may be required to ensure the entire root system is killed.