Ground covers are living solutions for weed control, forming a dense, protective layer of vegetation over the soil surface. These plants act as a permanent, self-sustaining mulch that replaces the need for continuous weeding and traditional material application. The goal of using a ground cover to “choke out” weeds is to establish a vigorous, low-growing plant community that actively prevents unwanted seedlings from germinating and growing. This method provides a low-maintenance, long-term strategy for managing bare soil, slopes, and difficult areas in the landscape.
How Ground Covers Suppress Weeds
Ground covers primarily suppress unwanted vegetation through a combination of physical and biological processes that limit the resources available to weed seeds and seedlings. The most immediate mechanism is physical shading, where the thick, low-lying foliage intercepts sunlight before it reaches the soil. Since many annual weed seeds require light exposure to break dormancy and germinate, blocking this light source effectively prevents new growth from emerging.
Established ground covers also engage in intense resource competition, aggressively drawing water and soil nutrients away from potential weeds. The dense root systems of these plants occupy the upper soil layers, depleting the moisture and mineral content that newly germinated weeds would need to survive. This competition severely stunts the growth of any weeds that manage to sprout, making them weak and non-invasive.
Some ground cover species employ a more sophisticated strategy known as allelopathy, which involves releasing specific biochemical compounds into the soil. These allelochemicals act as natural herbicides, inhibiting the germination and growth of neighboring plants. This chemical defense mechanism, observed in plants like certain Sedums, works synergistically with shading and competition to create a hostile environment for weeds.
Essential Traits of Effective Weed Blockers
Selecting a ground cover requires focusing on specific physical characteristics that guarantee rapid and complete soil coverage. A high-density, matting growth habit is fundamental, requiring plants to knit together into an impenetrable carpet that leaves no gaps for light or weed emergence. The foliage must be uniform and close to the ground to maximize shading.
The rate of spread is equally important; effective weed blockers must establish quickly to outpace the germination cycle of common weeds. Plants that spread rapidly via runners, stolons, or rhizomes colonize open ground in a single growing season, minimizing the opportunity for weed seeds to take hold. This rapid expansion ensures the ground cover is the dominant plant species from the start.
The root structure also contributes significantly to effectiveness. Ground covers with shallow, fibrous root systems are particularly good at occupying the top few inches of soil where the majority of weed seeds lie dormant. By aggressively colonizing this shallow layer, they create a dense, living root mat that physically and competitively excludes weed seedlings.
Top Aggressive Ground Cover Recommendations
Aggressive ground covers are successful weed suppressors because their vigorous growth habits align with the traits necessary for complete coverage. For areas receiving full sun, Creeping Phlox (Phlox subulata) is an excellent choice, forming a dense, low cushion of semi-evergreen foliage. Its ability to thrive in poor, sandy soil and full sun allows it to colonize challenging spots, creating a thick mat that prevents new growth.
Another sun-loving option is Creeping Sedum or Stonecrop, particularly varieties like ‘Angelina’ or ‘Dragon’s Blood’. These succulent ground covers are extremely drought-tolerant and form a colorful, moss-like carpet of foliage that spreads steadily. The dense mat efficiently blocks light and withstands environmental stresses without thinning out. Creeping Thyme (Thymus serpyllum) is recommended for sunny spots, forming fragrant, tight mats that tolerate light foot traffic. Varieties like Red Creeping Thyme grow densely, actively choking out weeds as they spread.
In shaded areas, Japanese Spurge (Pachysandra terminalis) is a classic choice, known for its year-round, deep green foliage that forms a thick, uniform cover. It spreads rapidly via underground runners, creating a dense, evergreen layer effective in dry shade conditions often found under mature trees. Vinca minor (Periwinkle) is another robust option for shade, featuring trailing stems that root at the nodes to quickly form a wide, interlocking mat of foliage. Its aggressive spreading habit makes it a nearly impenetrable barrier against weeds.
A final aggressive shade option is Bugleweed (Ajuga reptans), which forms a thick, low-growing mat of foliage, often with deep purple coloration. Bugleweed spreads rapidly via surface runners called stolons, quickly filling in large, shady areas. Gardeners must monitor its spread, as its aggressive nature makes it a superior weed blocker.
Installation and Management for Success
Successfully using ground covers depends heavily on initial site preparation and ongoing management. The most crucial first step is the complete removal of all existing perennial weeds before installation. Ground covers suppress new weed seedlings, but they cannot easily compete with established, deep-rooted weeds. Removing these mature plants, possibly using a non-selective herbicide or solarization, is necessary for long-term success.
To ensure the ground cover closes the canopy quickly, plants should be installed at closer spacing than typically recommended for slower-growing species. For aggressive varieties, spacing plants 6 to 12 inches apart allows rapid spread to quickly knit together and begin shading the soil. Once planted, consistent watering is necessary to encourage fast establishment and root development.
Because these plants are selected for their aggressive growth, containment is an ongoing management consideration. Boundaries next to lawns, walkways, or adjacent garden beds require regular attention to prevent migration into unwanted areas. Installing a physical barrier, such as plastic or metal edging buried a few inches into the soil, helps manage the spread of runners and rhizomes, keeping the weed-blocking mat confined to its intended space.