Retaining Walls & Rockeries

Seattle is a city built on hills. Our houses are arranged on these hills like a patchwork of theater seats, taking advantage of the remarkable views our part of the world has to offer. Of course, keeping all of these sloping properties from sliding to the bottom of their respective hills is a challenge. And rising to this challenge are thousands of retaining walls and rockeries. If you have a sloping property and need to build a retaining structure, Seattle is the place to explore for ideas. Here are a few of them.

For people who complain that concrete is too boring, this is a clever way to use the material. These walls form the front edge of a yard with a red brick house. The homeowners could have chosen masonry to match the house, but masonry walls would probably have been more expensive than these tinted concrete ones. A few bricks attached to the walls echo the brick of the house, making for a cohesive hardscape design.

Here is a concrete wall system that is clean and sophisticated. Finished with parallel grooves along the top and featuring built-in lighting for the steps (note the small rectangles along the wall), this is one of my favorites.

This type of wall, made of river rock, was popular in the Craftsman era. I doubt anyone builds walls like these much anymore. This one is in better shape than most I've seen and the plantings add to its charm.

Today concrete walls with a stone veneer, like this one, are more popular. These can be constructed more quickly, easily and affordably than walls built with stone only.

My landscape design instructor used to say, "The trouble with common plants is that they are used commonly." The same can be said of common building materials, like this concrete block. I know that these block systems are affordable and relatively easy to install. But aesthetically, they don't do much for me. Here, however, is a winning combination of planting and hardscape. The block walls literally set a stage for the plant material, which is what draws the eye.
[For more ideas, take a look at "Hillside Landscaping: A Complete Guide to Successful Gardens on Sloping Ground," from Sunset Books.]
Note also that instead of one very tall wall, there are two tiers, one set back from the first. From a design standpoint, this is good because it adds layers of color and texture instead of a monolithic and forbidding looking structure. From a legal standpoint, the design works, too. According to the building code in Seattle, any structure over 4 feet tall is considered a retaining wall and a permit is required before it is built. These tiered walls are each at or under 4 feet, thus avoiding the need for a permit.

Of course, no article on garden walls in this area would be complete without a mention of the classic Seattle rockery. Usually made of basalt, which is abundant in the Northwest, these walls are constructed without mortar. The gaps between the stones are perfect planting pockets for gardeners to fill with color, as you see below.

Lewisia

Years ago, a friend of mine, who then owned a small native plant nursery, asked me to help with her booth at a plant sale at the Bellevue Botanical Garden. At the time, I didn't know much about Northwest natives and I thought it would be a good way to spend some time with her and learn more.

As we unloaded her truck, she pointed to a flat of plants. "These are Lewisia," she said as if I should know the significance of that. "Keep an eye on them or they will disappear," she added, somewhat sternly. I looked at the plants. They didn't look like anything special. None were in bloom. The leaves formed a flat, fleshy rosette that looked like they could be related to Echeveria (hens and chicks). Surely she didn't mean that anyone would steal one of these when we weren't looking?!

We set up our display and she brought out signs with descriptions of the various plants, and for those not in bloom like the Lewisia, photos of the flowers. When I saw the photos, I began to understand why these plants might be of interest. These beautiful little alpine flowers will stop you in your tracks.

What I also didn't realize was that very few people at that time propagated Lewisia for sale. They weren't available at nurseries then (although the L. cotyledon you see in the photo above is one I bought at West Seattle Nursery several years ago). You would have to go up into the mountains, as she had, and collect seed or get the seed from someone who had. Getting the seed wasn't even half the battle. These plants aren't easy to grow. They need sharp drainage and a fair amount, but not too much, sun.

Of course, the plant enthusiasts at the sale that day already knew all of this. Once the sale began, word spread rapidly that we had Lewisia for sale. A crowd gathered. My friend could have sold that flat of plants 10 times over! She said she would sell only one plant to a customer. She knew how hard they were to grow and felt that if several gardeners each got a plant, there was a greater likelihood that some plants would survive than if just one or two people got them all. There was a lot of pleading and begging going on, but she stuck to that policy. We sold out of Lewisia in mere minutes.

Lewisia is much more available today than it was back then. But it still isn't easy to grow. That doesn't mean you shouldn't try. If you are interested and have a sandy, rocky spot, buy a plant and see what happens. Every summer when my Lewisia blooms, I'm glad I did.

If you'd like to learn more about Pacific Northwest native plants, I recommend Arthur Kruckeberg's classic reference, "Gardening with Native Plants of the Pacific Northwest."