Dollar weed, scientifically known as Hydrocotyle spp. and often called pennywort, is a common perennial weed that infests lawns and gardens in warm, temperate regions. This plant is considered an aggressive pest because of its rapid spread and persistence, which directly competes with desirable turfgrass and ornamental plants. Addressing an infestation requires a comprehensive approach that targets both the visible plant and the underlying environmental conditions that allow it to thrive.
Identifying Dollar Weed and Its Preferred Habitat
The dollar weed plant is easily recognized by its distinctive, bright green, coin-shaped leaves, which give it its common name. The leaves are round, sometimes with scalloped edges, resembling miniature lily pads. A defining morphological characteristic is the attachment point of the leaf stem, or petiole, which connects near the center of the leaf, like an umbrella. This feature distinguishes it from similar-looking weeds such as dichondra, where the stem attaches at the leaf margin.
This weed thrives in consistently moist or wet conditions and is often considered a water-loving plant. It is commonly found in areas with poor drainage, compacted soil, or where irrigation is excessive. Because it is semi-aquatic, its presence often serves as an indicator that the soil moisture levels are too high for optimal turf health. The plant proliferates during warm seasons, actively spreading through both seeds and an extensive network of underground runners called rhizomes.
The True Impact on Lawns and Gardens
Dollar weed is highly detrimental to a healthy lawn because of its aggressive, creeping growth habit. It spreads rapidly via rhizomes and surface stolons, allowing it to quickly colonize large areas and form dense, low-growing mats. This invasive growth effectively chokes out desirable turfgrasses and ornamental plants by competing for sunlight, water, and available soil nutrients.
The dense matting structure compromises the uniform appearance of a lawn, creating unsightly patches of bright green foliage. As the dollar weed dominates the area, the underlying grass becomes thin and vulnerable, leading to a decline in overall lawn health and aesthetics.
Cultural Practices for Long-Term Suppression
Since the weed requires excessive moisture, adjusting irrigation practices is the most important cultural practice. Lawns should be watered deeply but infrequently, aiming for about one to one-and-a-half inches of water per week, allowing the soil surface to dry out between watering sessions. This encourages the turfgrass to develop deep roots while making the surface soil inhospitable to the shallow-rooted dollar weed.
Improving soil drainage is essential, particularly in low-lying areas where water tends to pool. Core aeration can help break up compacted soil, improving water penetration and reducing surface moisture. Raising the mowing height of the turfgrass promotes a denser, taller canopy. This increased shade inhibits dollar weed growth and germination, giving the desired grass a competitive advantage by limiting the weed’s access to sunlight.
Maintaining proper turf nutrition through regular, balanced fertilization encourages a thick, healthy lawn that naturally crowds out weeds. Using slow-release, nitrogen-based fertilizers can promote steady grass growth without encouraging a flush of weed growth.
Targeted Removal Strategies
For small, isolated patches, manual removal can be effective, but every part of the root and rhizome system must be carefully dug out. For widespread infestations, chemical control using selective post-emergent herbicides is the most practical option.
Products containing active ingredients such as 2,4-D, dicamba, and mecoprop (MCPP), often sold as “three-way” broadleaf weed killers, are commonly recommended for targeting dollar weed without harming most turfgrasses. These herbicides work best when applied to the actively growing weed foliage. Homeowners should always confirm the product is safe for their specific turf type, as some ingredients require reduced rates on sensitive grasses like St. Augustinegrass and centipedegrass.