Steep and moderate slopes can be found in virtually any setting and can present landscape challenges. Perhaps it is time to tackle your slope to change it from a challenge into an opportunity.
You can create a productive vegetable garden, a beautiful landscape of flowers and trees, or a combination of the two. The project can be of any size, from small to massive, depending on your interest and your site.
Orientation
Take a good look at your property to determine the orientation and how much sun and shade each area receives. Retaining walls are frequently the most effective way to create level growing areas (terraces) and to reduce soil erosion. How much level space is possible will depend on the contour of your land and how much soil must be added or removed.
The goal should be to move as little soil as possible. Small slopes can usually be modified by hand, using shovels and wheelbarrows. Extremely steep slopes that require the use of earth-moving equipment will likely also require the services of a professional soils engineer, drainage engineer, landscape architect/contractor, or a combination of these.
Be sure to determine ahead of time if permits are needed for the work you plan.
Retention
Retaining walls can be constructed from many materials including boulders, landscape timbers, precast concrete blocks, bricks, and poured concrete. Masonry materials or concrete will cost more but will last longer than wood. If you create a series of terraces, you will need a way to access the level areas.
Include ramps so you can easily move equipment and materials onto and between your terraces. Terraces and pathways that are easy to navigate add to the aesthetic and financial value of your property. A garden bench overlooking your garden can provide a break from garden chores as well as a private space to meditate.
Drainage
Good drainage is key to a successful terrace garden. Depending on the amount of surface and underground water, you may need to install a perimeter drain around the area to be terraced to divert water.
If the native soil of the slope is primarily heavy clay, a retaining wall made of poured concrete or tight-fitting timbers could result in a terrace with restricted drainage.
It may be necessary to leave space between timbers or drill 1-inch holes every 18- to 24-inches to allow excess water to escape. Perforated plastic drainpipes covered by a layer of rocks placed in the bottom of the excavated area that is to become the terrace can provide additional drainage.
Additional tips
Terrace width is determined by how you will use your terrace and what you are going to plant. Make sure you have a water source nearby to provide supplemental water to your plants when needed. A soaker hose or drip system may be a simple solution and provides flexibility.
Before bringing additional soil onto your site, make sure the soil has been composted to kill aggressive weed seeds.
Get an idea of what others have done and how much work will be involved by looking at landscape design books, websites, and examples in your community. Perhaps this is the year your challenging slope becomes a beautifully terraced landscape.
Judy English is a Washington State University-certified Clallam County Master Gardener.
Newcomers invited to start ‘Digging Deeper’
Make sure to join us for the upcoming Digging Deeper presentation “Gardening for Newcomers to the North Olympic Peninsula,” by Margery Whites, a Clallam County Master Gardener, from 10:30 a.m.-noon on Saturday, Aug. 20, at the Woodcock Demonstration Garden, 2711 Woodcock Road.
“Gardening for Newcomers” is free and open to the public but limited to the first 30 people who sign up for the session. Register at brownpapertickets.com/event/5524883 or extension.wsu.edu/clallam/master-gardener-calendar.
Whites will describe local growing conditions and how they impact gardening. She will help wanna-be gardeners examine the topography of their property, soil conditions and environmental exposures (e.g., wind, sun, rainfall) so that they can select the best location for their garden and the right plants. She will also discuss some of the challenges of gardening in our area including our cool growing season, excess rainfall in winter and spring, drought conditions in mid-summer, and local animal life.
Note: Donations to help support the WSU Clallam County Extension Master Gardener program or Master Gardener Foundation of Clallam County are appreciated.
