While some homeowners prefer property that is as flat as a pancake, as a garden designer, I find that a few ups and downs add an appealing interest to a garden. However, steep hillsides can limit your gardening options and create drainage and maintenance problems. Whether you are faced with a challenging hillside, an uneven backyard or just want to add some new contours to your garden, retaining walls are a helpful tool in reshaping your landscape.
Define the term
Retaining walls are different from freestanding garden walls because they are designed to contain the weight of soil pushing against them. Depending on the steepness of the slope and the height of the wall, the pressure on the wall can be significant, especially when the force of heavy rains or melting snow is added. It's important to take those factors into consideration when designing the wall to make sure it will be stable and long lasting.
Study your terrain
Before modifying your property, study the current drainage patterns and soil types. Seemingly innocent grading and minor construction can trigger astonishing changes that may result in severe soil erosion or water pooling up against foundations of buildings. Be aware that many sites slope in more than one direction and may not incline at a uniform rate, but are undulating or rolling.
Inquire about codes
As you consider re-contouring various areas, save yourself some time and trouble by checking into your local area's building codes. Many municipalities require building permits for retaining walls. Also, find out how close to the property line you may build and if you'll need concrete footings or steel reinforcements. Simple, low retaining walls on gently sloping, stable ground are manageable do-it-yourself projects. A taller wall with grading and code requirements may require professional help.
The best wall designs not only help create more useable areas to enjoy, but they enhance the style of your home and garden. One way to achieve that look is to use materials that repeat or complement your home's architectural style. The spectrum of wall materials available is enormous; there are wood walls made from ties or boards, dry stack walls from stones, modular concrete blocks that lock together, mortared walls from brick, stone or concrete block, as well as poured concrete walls with or without stone veneers. While it is tempting to buy "off the shelf" materials offered at building centers, the right choice for your home may be something different. For instance, if you have a brick home, using the same color and style of brick in the retaining wall helps create a visual connection between your garden and home. Natural stone works well for a Craftsman cottage while pressure treated wood and used railroad ties would add rustic charm to a cabin.
Make more than walls
With a little imagination, retaining walls can do more than just hold soil in place. They can be an exciting design element, adding texture and depth to your garden. To explore the possibilities, visit public gardens, look through magazines or pick up design literature from suppliers for some creative ideas. I've used retaining walls in my designs to create a sense of enclosure for outdoor rooms, shape the outlines of cascading water features, create pathways on a sloping hillside, group plantings in framed beds and to add curb appeal to a home's entry. On extreme slopes, tall, imposing walls, can be highlighted with built in planting pockets, or softened with cascading varieties of plants that tumble over the top. When steps are combined with retaining walls both are enhanced: the steps break up the wall's expanse, and the walls adds interest to the stairway.
Highlight with plants
For any garden, on the slope or terraced with retaining walls, you should select plants that appeal to you and that are adapted to your climate and growing conditions. Often, you are dealing with less-than-ideal soil, so add organic matter to give your plants a better chance at taking hold. If your site is difficult to get to and makes maintenance challenging, consider plants that demand little care, such as a mix of low, spreading shrubs or plants that develop dense or wide-spreading roots to help stabilize the soil. A cascade of flowers and foliage adds charm to any retaining wall. There are many plants that billow, trail or climb. To add appeal to a dry wall made from staked stone, try planting in the crevices. Many small plants, including rock garden plants are good choices.
Great Plants for Retaining Walls
- Luscious™ Citrus Blend™ Lantana
- Cheddar Pink (Dianthus gratianopolitanus)
- Creeping Jenny (Lysimachia nummularia)
- Ground morning glory (Convolvulus sabatius)
- Thyme (Thymus)
- Dolce® Key Lime Pie Heuchera
- Diamond Frost® Euphorbia
- Silver Chiffon™ Snow in Summer (Cerastium tomentosum)
- Blue Crown™ Blue Fescue (Festuca)
- Supertunia® Petunia
- Superbells® Calibrachoa
- Bluebird Nemesia
- New Wonder® Scaevola
- Charmed® Wine Oxalis
- Laguna™ Sky Blue Lobelia
- Snowstorm® Giant Snowflake® Sutera