Kidney weed is a common name for a persistent, low-growing plant that often infiltrates lawns and gardens, creating a dense, fast-spreading mat of foliage. Its vigorous growth habit allows it to quickly outcompete turfgrass and other groundcover, making it a difficult weed to control.
Clarifying the Plant’s Identity and Scientific Classification
The common name “Kidney Weed” is ambiguous and can refer to more than one species. While sometimes applied to Dichondra repens (particularly in Australian horticulture), the plant most often encountered as a persistent lawn invader in North America and Europe is Glechoma hederacea, also known as Ground Ivy or Creeping Charlie. This plant, which is the primary focus, is a member of the mint family (Lamiaceae).
Glechoma hederacea is a perennial, evergreen creeper that can be identified by its square stems and small, opposite leaves that are kidney-shaped to heart-shaped with scalloped edges. When crushed, the foliage releases a strong, musky mint aroma typical of the Lamiaceae family. In the spring, the plant produces small, tubular, blue-violet flowers that grow in clusters in the leaf axils.
Invasive Status and Management
Glechoma hederacea is considered a problematic species in managed landscapes due to its aggressive growth pattern. It spreads primarily through stolons—horizontal stems that creep along the soil surface and readily root at each node, quickly forming a dense carpet. This vegetative propagation makes mechanical removal difficult, as any small stem fragment left behind can easily re-root and regenerate the plant.
Effective management requires a combination of cultural and chemical strategies. Cultural control involves improving turf health, as a dense lawn can outcompete the weed. This includes mowing at a higher height (around three inches) and ensuring proper soil fertility and drainage. Because Glechoma hederacea prefers shady, moist conditions, increasing light and air circulation by trimming nearby trees and shrubs can help weaken its foothold.
For established or widespread infestations, chemical control is often necessary. Systemic post-emergent herbicides containing active ingredients like triclopyr are the most effective option, especially when applied in the fall or early spring. These chemicals are absorbed by the foliage and translocated throughout the plant, including the root system and stolons, offering a more complete eradication than non-systemic treatments.
Traditional Uses and Modern Claims
The common name “Kidney Weed” and its relatives, like “Alehoof,” reflect the plant’s long history in traditional European herbalism. Historically, the plant was used as an astringent and mild expectorant, often employed in tonics and teas to support kidney and lung function, as well as to treat respiratory issues like persistent coughs and bronchitis. This traditional application for urinary and kidney ailments is the likely source for the modern common name.
The plant’s biological activity is attributed to its complex chemical composition, including volatile oils and various phenolic compounds. Specific constituents include the bitter principle marrubiin, flavonoids, and phenolic acids like rosmarinic acid, known for its antioxidant and anti-inflammatory properties. Despite this traditional use, modern medical research has not broadly validated the historical claims, and human clinical trials are largely absent.
The plant does contain volatile oils, including pulegone, which can be a concern. Glechoma hederacea has been shown to be toxic to grazing animals, particularly horses, if consumed in large quantities, leading to symptoms such as labored breathing and excessive salivation. Some sources caution against its use by individuals with existing kidney or liver conditions, underscoring the need for careful consideration outside of professional medical guidance.