Planting ground cover on a slope is a unique landscaping challenge because gravity constantly threatens to pull soil, water, and plants downhill. Ground cover plants are low-growing species that form a dense, protective mat over the soil surface, which is the primary defense against erosion. On an incline, their intertwining roots create a subterranean network that physically holds soil particles in place, stabilizing the slope. Successfully establishing this vegetative layer requires a specialized approach to address the immediate risk of soil displacement and poor water retention, beginning long before the first plant is placed in the ground.
Preparing the Slope for Planting
The initial preparation of a slope is a determining factor for long-term success, focusing on stabilizing the area before new plants are introduced. Clearing existing vegetation should be done carefully to minimize soil disturbance, often requiring hand removal of weeds or the use of solarization. After clearing, assess the soil for drainage and composition, as slopes often have poor, fast-draining soil that may benefit from light amendment to improve water retention.
A temporary measure is the installation of erosion control materials to physically secure the soil during the plant establishment phase. This typically involves using biodegradable erosion control blankets or jute netting, which are rolled down the incline and secured with stakes or staples. At the top of the slope, excavate a shallow trench (about six inches deep and wide) to anchor the blanket and prevent water from running underneath. This netting provides immediate protection from runoff, creating a stable microenvironment where plant roots can begin to take hold.
Selecting Ground Cover for Erosion Control
Selecting the correct plant species is essential, as the chosen ground cover must possess specific characteristics to function effectively. Plants best suited for slopes have deep, fibrous, or aggressive root systems that penetrate the soil deeply and spread laterally. This extensive root network binds soil particles together, anchoring the entire slope against shear forces caused by water movement.
Slopes tend to dry out quickly due to increased sun exposure and rapid water runoff, making drought tolerance another important criterion. Species such as sedums, creeping junipers, and ornamental grasses are frequently chosen because they are hardy and require minimal moisture once established. The plant should also exhibit a fast-spreading habit, utilizing runners or rhizomes to rapidly cover the exposed soil surface and suppress weed competition. Choosing plants that form a thick, dense mat above ground helps slow the velocity of rainfall, reducing impact energy on the soil.
Essential Planting Techniques for Slopes
The physical act of planting on a slope must be adapted to counteract gravity and minimize soil displacement. Work should always proceed from the top of the slope downward, which prevents walking on newly planted areas and avoids dislodging secured soil or plants. When creating planting holes, disturb the soil as little as possible, often utilizing smaller plant sizes like plugs to reduce excavation.
Position the plant slightly uphill, angling the root ball and the crown toward the top of the slope rather than planting straight vertically. This slight upward tilt helps prevent the plant from being pulled out of the ground or having its roots exposed by soil slippage. After placing the root ball, tightly firm the soil around the base to eliminate air pockets and ensure optimal root contact. Dense planting is recommended to achieve quick, full coverage, which helps outcompete weeds and stabilize the soil rapidly.
Long-Term Establishment and Care
After installation, the focus shifts to ensuring the ground cover establishes a robust root system capable of permanent slope stabilization. Immediate care involves a watering strategy designed to prevent runoff by applying water slowly and deeply for maximum soil absorption. Using a hose with a gentle nozzle or drip irrigation is recommended to control pressure and avoid washing away newly set plants or loose soil. Even drought-tolerant species require consistent irrigation for the first one or two growing seasons until their roots are fully established.
The application of mulch is necessary to retain moisture and regulate soil temperature, but material choice is important to prevent sliding down the incline. Shredded wood mulch or pine needles are superior choices over light, fine materials, as their interlocking nature helps them stay in place on a grade. Apply this layer at a depth of two to three inches, keeping it away from the plant stems to prevent rot. Monitor the mulch regularly for washout or thinning until the ground cover forms a complete, self-sustaining carpet.