Pachysandra (Japanese Spurge) is a popular, dense, evergreen groundcover known for thriving in shaded areas where turfgrass often fails. It forms a lush, uniform carpet of glossy green foliage, making it a desirable solution for landscaping under trees and shrubs. Homeowners must understand its vigorous spreading nature, as this tendency makes it an effective groundcover but also a potentially aggressive one.
Mechanisms of Spread
The speed of Pachysandra’s expansion is primarily driven by its unique vegetative growth structure, centered on underground stems known as rhizomes. These creeping, horizontal root systems extend outward from the established plant, anchoring themselves in the soil. New, upright shoots emerge from these rhizomes, creating the dense, mat-like colonies. While vertical shoot growth is minimal, the horizontal spread of the rhizomes determines the actual rate of coverage, allowing the plant to quickly colonize an area. Seed dispersal is a secondary and far less common method of reproduction in garden environments, meaning nearly all expansion is root-driven.
Environmental Conditions That Accelerate Growth
The actual rate of spread varies significantly based on the surrounding environmental conditions. The fastest growth occurs in environments that mimic Pachysandra’s native forest floor habitat, which includes deep to partial shade. Direct sunlight causes the foliage to bleach or burn, severely limiting growth and spread in bright, open areas.
Pachysandra thrives in moist, well-drained soil that is rich in organic matter and slightly acidic, ideally with a pH between 5.5 and 6.5. When these conditions are met, a new planting can establish a continuous, dense mat of cover in approximately three years if initial cuttings are spaced six to twelve inches apart. The rate of spread is significantly slowed in dry, compacted soils or in areas with alkaline soil, where the plant struggles to establish a robust rhizome network.
Managing Unwanted Expansion
Since Pachysandra spreads through a continuous network of rhizomes, managing its expansion requires a strategy focused on containing this root system. The most effective containment method for controlling spread into lawns or adjacent beds is installing a physical barrier. Edging materials, such as plastic landscape edging, should be installed approximately six inches deep to block the shallow-growing rhizomes from creeping into unwanted areas.
Manual Removal
For established areas where the plant has already spread beyond its boundaries, manual removal is an option, though it requires diligence. Every piece of rhizome left in the soil can potentially sprout a new plant, so the entire root mat must be carefully dug out when removing the groundcover. All plant debris, including roots and stems, must be completely removed from the site and should not be composted, as these parts can remain viable and re-establish growth.
Chemical Control
Chemical control offers a means of eradication for large, unwanted patches, typically using the systemic herbicide glyphosate. For the product to be effective, it should be applied to the foliage of actively growing plants, often in the fall. This timing allows the chemical to be transported down into the root system. A concentration of around a two percent glyphosate solution, mixed with a surfactant to ensure absorption, is recommended for this purpose.