Ground cover plants on sloped terrain address the unique challenges presented by gravity and water runoff. These specialized plantings serve a dual function: acting as a biological defense against soil erosion while providing aesthetic improvement to difficult-to-maintain areas. Traditional turfgrass and garden beds often fail on inclines because rapid water movement prevents soil saturation and washes away topsoil. Selecting the right plant material is paramount to transforming a vulnerable hillside into a stable, thriving ecosystem.
Evaluating Your Slope and Site Preparation
Before planting, thoroughly assess the slope’s physical characteristics to ensure long-term success. Start by determining the slope’s grade, measured as the rise over the run. Slopes exceeding a 3:1 ratio (three-foot horizontal run for every one-foot vertical rise) are highly prone to erosion and require robust stabilization. Analyzing the drainage pattern is also important, as the top often dries out quickly while the bottom may be prone to waterlogging.
Existing soil quality must be evaluated, as topsoil on slopes is frequently thin, less stable, and low in nutrients. While amending challenging slope soils is tempting, focus instead on stabilization and creating proper planting pockets. The slope’s orientation dictates sun exposure and creates microclimates. For example, a south-facing slope will be hotter and drier than a north-facing one, significantly influencing plant selection.
Site preparation involves clearing existing weeds, which compete with new plantings for moisture and nutrients. For moderate to steep slopes, temporary stabilization is crucial during establishment. This is often achieved using biodegradable erosion control blankets made from materials like coir or straw. Secured with stakes, these blankets temporarily shield the soil and retain moisture until the plant roots can take over the anchoring function.
An effective technique involves creating a small planting pocket or mini-retaining wall on the downhill side of each new plant. This barrier, made from sod or a small rock, slows water flow long enough for it to soak into the root zone. When watering new plants, deep and infrequent application is necessary to encourage deep root growth. Using a drip system or soaker hose prevents surface runoff and further erosion.
Key Traits of Effective Slope Ground Covers
A plant’s success in stabilizing a slope is determined by its below-ground architecture and spreading habit. Effective erosion control plants possess a dense, fibrous root system that acts like a mesh network, physically binding soil particles together. This root mass is the primary mechanism resisting gravitational pull and the scouring action of surface water runoff.
Deep roots provide a secure anchor, penetrating soil layers to hold the hillside mass, while mat-forming roots create thousands of tiny anchors near the surface. This robust rooting makes native grasses and strappy ground covers superior for erosion control. The dense root network also improves soil structure, increasing porosity. This allows water to infiltrate slowly instead of running off the surface.
Above ground, the ideal slope cover exhibits a dense, low-growing, and aggressively spreading habit. This growth creates a continuous canopy that acts as a natural mulch, protecting the soil from the direct impact of raindrops. The thick foliage shades the soil, suppressing weed growth and reducing moisture evaporation. This is important given the typically dry conditions found on slopes.
Durability and low maintenance are paramount traits, as tending to plants on a steep incline is difficult. Once established, plants must tolerate drought and poor soil conditions, requiring minimal supplemental water or fertilizer. Selecting species adapted to the exposed, fluctuating conditions of a hillside ensures they thrive and provide reliable, long-term stabilization without intensive upkeep.
Specific Plant Recommendations for Different Exposures
Full Sun and Drought Tolerant Slopes
Areas receiving six or more hours of direct sunlight, particularly south or west-facing slopes, require plants highly tolerant of heat and dry soil. Creeping Juniper (Juniperus horizontalis) is a favored evergreen option known for its low, sprawling habit and excellent root matting capability. Cultivars like ‘Blue Rug’ grow prostrate, offering dense coverage and drought resistance once established.
Stonecrop (Sedum species) is a top choice, thriving in poor, rocky, and dry soils where other plants fail. Its shallow, dense root system and ability to store water make it ideal for the extreme conditions on the upper parts of a sunny slope. For larger areas, low-growing shrubs like Grow-low Sumac (Rhus aromatica ‘Gro-Low’) offer deep, soil-anchoring roots and a dense stem structure that halts erosion.
Ornamental grasses and sedges provide exceptional stabilization due to their extensive, fibrous root systems.
Recommended Full Sun Plants
- Clumping grasses like Little Bluestem (Schizachyrium scoparium) and Muhly Grass (Muhlenbergia capillaris) develop a firm root mass highly effective at anchoring soil.
- Creeping Thyme (Thymus serpyllum) is a fragrant, low-growing perennial that spreads quickly, providing dense, durable cover for smaller sunny slopes.
Shade and Partial Shade Slopes
Slopes under tree canopies or facing north require ground covers that tolerate lower light levels while possessing robust root systems. Periwinkle (Vinca minor) is a classic evergreen choice for shaded hillsides. It spreads quickly by trailing stems that root as they creep, providing dense, mat-forming growth and reliable, year-round soil protection.
Spotted Dead Nettle (Lamium maculatum) is an excellent shade-tolerant option, forming a dense mat with attractive variegated foliage. It spreads by stem rooting and runners, effectively choking out weeds and stabilizing the surface soil layer. Barrenwort (Epimedium species) is a perennial that thrives in dry, woodland conditions, ideal for slopes where competing tree roots create dry shade.
Mondo Grass (Ophiopogon japonicus) and Lilyturf (Liriope muscari) are grass-like plants that form dense clumps and spread via underground rhizomes. These rhizomatous systems create an interwoven network of roots highly effective at holding soil. They tolerate both sun and shade, though they prefer filtered light. Bugleweed (Ajuga reptans) is a fast-spreading perennial that uses stolons to quickly cover large areas, making it a reliable option for rapid erosion control in partial shade.