Another unique and challenging site involving a steep slope on a highly visible area, with years of erosion degrading the soil quality. Green Jay Landscape Design was hired to beautify the slope with a functional planting that would also stabilize the soil and prevent further erosion onto the street below. A suite of erosion control devices was deployed in this project, coupled with a site-specific plant palette that catered to all the microclimates.
Watch an interview with Jay Archer and Uziel Crescenzi below on the project!
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Analyzing Slope Site Conditions
This roadside slope was planted with mostly vinca and pachysandra, both shallow rooted, exotic plants that did little to stabilize the soil, especially during storm events. As a result, the soil depth was low, and it lacked adequate nutrients. During site analysis, we mapped the various light conditions, with a full sun section at the top of the slope, progressing to full shade by the bottom of the slope.
Designing a Plant Palette for Erosion Control
The plant palette needed to include deeply rooted native plants to secure the hillside as stormwater moves quickly down the slope. Deeply rooted plants are also better able to access water reserves deep in the soil during periods of drought.
This palette included many native woodland perennials, flowering shrubs, and ferns, as well as fast growing evergreen groundcover shrubs to maintain function during the winter months. The goal was to choose plants that would spread quickly to cover the slope, while also providing a variety of root depths for stabilization and look beautiful from the street!
As with all of our planting designs, ensuring a succession of blooms, from early spring to late fall, not only is visually appealing, but also supports critical pollinator species.
Erosion Control Devices for a Steep Slope
Until the planting matures, the root systems are less robust. We install with various erosion control materials to help support and stabilize the slope as the plants’ roots expand.
One example are erosion socks, cloth tubes filled with woodchips, that are staked into the ground across the slope to create a physical interruption. We surround the socks with high quality soil and plant around them. We use buried boulders for a similar purpose: interrupting stormwater flow, slowing it down and thereby allowing it to infiltrate into the surrounding soil. On this project, we also incorporated found logs, pinning them into the soil as an above-ground version of an erosion sock. The rustic, naturalistic aesthetic they provide to this woodland inspired garden is fitting.
The soil brought into this project restored the organic matter previously lost to erosion. We also added biochar compost, which improves the water holding capacity of the soil as well as the soil structure. Soil structure is important because proper structure with air pockets allows plant roots to expand. Biochar is also a host material for soil microbes, which contribute greatly to plants’ immune response.
Lastly, we stake down jute netting across the entire site and plant directly into it. The netting secures each plant onto the slope and biodegrades over time as the plants mature. The netting is covered with mulch and not visible after installation.
We also constructed a bioswale with stone baffles (larger horizontal pieces of stone) which effectively interrupt and slow down stormwater, diverting it out to the sides where it can infiltrate into the soil.
Slope Landscaping Project Outcomes
Now that this project is mature, we can safely say that the erosion control devices were effective in stabilizing the integrity of the slope, preventing erosion, and conserving soil. The planting has filled in nicely and continues to provide season-to-season habitat for wildlife and pollinators The clients and their neighbors are happy with the biodiverse aesthetic of the hillside, and enjoy watching something new bloom, seed or berry every week.
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