Ground Elder (Aegopodium podagraria), also known as Bishop’s Weed or Goutweed, is an aggressive and difficult-to-control invasive weed in garden and landscape settings. Native to Europe and Asia, this perennial was historically introduced as a medicinal herb, particularly for treating gout, which explains the name podagraria and the moniker Goutweed. Despite its past uses, it is now considered a pest due to its ability to colonize and overwhelm cultivated ground. Successful management requires understanding its physical characteristics and its unique mechanism for underground spread.
What Ground Elder Looks Like
Correctly identifying Ground Elder is the first step toward effective control, as it can be confused with other plants, including toxic species in the carrot family (Apiaceae). The leaves are a key identification feature, typically appearing as twice-trifoliate. This means the leaf stalk divides into three sections, which then divide again into three leaflets, often resulting in nine leaflets. These leaflets are oval with serrated edges, starting as a light apple-green color in spring and darkening to a matte finish as they mature.
The stem structure provides a distinctive identifier. Stems are hollow, green, and possess a triangular cross-section with a shallow groove running along one side. The plant forms a low, dense mat of foliage, usually around 50 centimeters high, but flowering stems can reach up to a meter tall in summer. These taller stems bear small, white flowers arranged in flat, umbrella-shaped clusters (umbels), similar to Cow Parsley. Gardeners may also encounter the variegated variety, which has cream or white edges on its leaves, though this form can sometimes revert to the more vigorous, solid-green wild type.
Understanding Its Invasive Nature
Ground Elder is difficult to remove due to its extensive underground network of rhizomes, which are modified stems used for vegetative reproduction. These creamy-white, fleshy, and brittle rhizomes form a dense, shallow web just beneath the soil surface. The plant spreads rapidly, with rhizomes capable of extending between 15 to 90 centimeters annually.
A challenge arises because these rhizomes are equipped with buds at regular intervals, each capable of sprouting a new plant. Even a tiny fragment of rhizome, sometimes as small as one centimeter, can regenerate, making standard digging techniques counterproductive. Fragmentation is the main vector for spread, especially when the root system is inadvertently broken up during clearing. Once established, Ground Elder forms a dense monoculture, effectively outcompeting native plants by monopolizing available sunlight, water, and soil nutrients.
Comprehensive Eradication Methods
Eradicating Ground Elder requires persistence and a multi-season commitment, often combining several control strategies due to its robust rhizome system. For smaller patches, manual removal is a viable non-chemical option, but it must be meticulously executed. This involves using a garden fork to gently loosen the soil and trace the entire length of the rhizomes, ensuring every segment is removed. When removing the plant from established flower beds, it is often necessary to temporarily lift desirable plants, wash the soil from their roots, and repot them to ensure no rhizome fragments remain entangled.
For larger infestations, or where digging is impractical, smothering or exclusion is effective. This technique involves covering the affected area with an opaque material, such as thick black plastic sheeting or heavy cardboard, to completely block sunlight. The covering must extend well beyond the visible patch of Ground Elder and remain in place for a minimum of one to two full growing seasons to fully deplete the energy reserves stored in the deep rhizomes. Repeated cutting of the foliage throughout the growing season, which starves the underground system of energy, is an alternative method for areas that cannot be covered, such as lawns.
Chemical control offers the quickest option for severe infestations, though it should be used judiciously. Systemic herbicides, such as those containing glyphosate, are the most effective because they are absorbed through the leaves and translocated down to the rhizomes. Application is most successful when the plant is in active growth, typically in summer, as the mature leaves maximize the herbicide’s movement through the plant’s vascular system. Multiple applications are usually necessary, and because glyphosate is non-selective, surrounding desirable plants must be shielded with plastic or cardboard to prevent accidental damage.
To prevent re-invasion from adjacent areas, containing the weed is a necessary long-term strategy. This can be achieved by installing a solid physical barrier, such as metal or plastic edging, sunk deep into the ground along the boundary to block the horizontal spread of the rhizomes. Any soil removed during excavation should never be added to a standard compost pile, as rhizome fragments will likely survive and be redistributed. Instead, the debris should be bagged and disposed of or subjected to hot composting that reaches temperatures high enough to destroy the plant material.