Ground cover refers to any material, organic or inorganic, or low-growing plant spread over the soil surface in gardening and landscaping. Ground covers manage and improve the landscape by protecting the soil from erosion, conserving moisture, and regulating soil temperature. Their most valued purpose, however, is the effective suppression of unwanted plant growth, often called weeds. Selecting the appropriate material requires understanding how it creates a hostile environment for weed seeds and seedlings.
How Ground Covers Suppress Unwanted Growth
Ground covers achieve weed suppression through both physical and biological means that limit the resources available to opportunistic plants. The most direct method is physical blockage, where a dense layer of material or foliage prevents light from reaching the soil surface. Weed seeds require light to germinate, so this shading mechanism effectively stops growth before it can start.
Living ground covers and organic mulches compete for resources like water and soil nutrients. By establishing a dense root system and canopy, the desirable cover crops intercept moisture and dissolved minerals, starving weed seedlings. Certain plants, known as allelopathic species, employ a biological strategy by releasing biochemical compounds into the soil. These natural chemicals directly inhibit the germination and growth of neighboring weed species, acting as a natural herbicide.
Inorganic Materials for Immediate Weed Control
Non-living materials offer rapid and long-lasting solutions for weed management. Organic mulches, such as shredded bark, wood chips, or pine needles, suppress weeds by blocking light and enrich the soil as they slowly decompose. The disadvantage is that they require regular replenishment, typically every one to three years, and can sometimes harbor weed seeds if not sourced carefully.
In contrast, inorganic options like landscape fabric and gravel provide a permanent physical barrier. Landscape fabric effectively blocks light and creates an impermeable layer that stops weeds from emerging. However, these materials do not contribute to soil health; fabric can impede the exchange of air and water, potentially raising soil temperatures to unhealthy levels for plant roots. Gravel and stones are durable and low-maintenance but lack the soil-improving qualities of organic mulches and are difficult to remove once installed.
Selecting Living Ground Covers That Outcompete Weeds
The most effective long-term weed control solution is a dense, living plant cover that sustains itself and aggressively outcompetes invaders. Selection must be tailored to specific site conditions, including sunlight, soil drainage, and climate zone. The best plants for this purpose have a rapid spread rate and a thick, continuous canopy that completely shades the soil.
For sunny locations with dry, well-drained soil, low-growing Sedum varieties, or Stonecrop, are excellent choices, forming a succulent, colorful mat that thrives in poor conditions. Another sun-lover is Creeping Thyme (Thymus serpyllum), which forms a dense, woody carpet that handles light foot traffic and releases a pleasant scent when disturbed. These plants are highly drought-tolerant once established, reducing the need for irrigation that can encourage weed growth.
In shaded or partially shaded areas, Vinca minor (Periwinkle) is a reliable option with glossy, evergreen leaves that spread via trailing stems and root where they touch the ground. Similarly, Ajuga (Bugleweed) is an aggressive, fast-spreading plant that forms a dense, low mat of dark foliage, effectively choking out weeds where turfgrass struggles. Selecting a plant aggressive enough to fill in quickly, but not so invasive that it becomes a problem, depends on the gardener’s preference and the size of the area.
Preparation Steps for Effective Installation
The success of the installation, whether using living or inorganic ground cover, depends almost entirely on the initial site preparation. The first step is the thorough removal of all existing weeds, especially perennial weeds with deep taproots or rhizomes. Failing to eliminate these established plants allows them to grow up through the new cover material.
The soil should then be loosened to a depth of six to twelve inches to improve drainage and aeration, encouraging healthy root development for living covers. Incorporating organic amendments like compost or aged manure enhances fertility and soil structure, giving desirable plants an advantage over weed seeds. Proper application depth or spacing is necessary for maximum effectiveness. Mulches should be applied in a layer two to four inches deep, and living plants should be spaced according to their mature spread to ensure the canopy closes quickly, preventing light from reaching the soil.