The Power of Walls

Walls can do amazing things for a garden. Here in Eugene we rarely see free-standing walls enclosing spaces, but retaining walls abound. I’ve visited many hillside gardens in Eugene that would be just about impossible to cultivate or enjoy without the transformative power of terracing and retaining walls. Materials vary. Poured concrete is practical and can also look great in certain settings. Railroad ties and treated lumber are relatively cheap. Concrete blocks of various kinds are popular, but to me they always look like an opportunity missed. Natural stone seems the best and most adaptable solution, and stone walls, like stone itself, come in many styles.

Twenty years ago, my husband and I moved to a house on a hillside.  The sloping backyard was easy enough to get around on and certainly well within the angle of repose for freshly dug soil and wheel barrows. But I soon realized that a garden with no level spots made me uncomfortable. It was not restful to look at, and there was no place to put a bench. The fix was simply to excavate two flat places (for a sitting area below and a small lawn above) with a flight of wide steps curving up the middle. Dry-stacked (that is, without mortar) basalt retaining walls two to three feet high were built against the cuts on the uphill side of each level area.

The effect of these simple, inexpensive walls was dramatic. They were nice to look at, they gave us useable living space and they provided some organizing structure and the sense of repose I needed. They were not, however, built well, and after 15 years, around the time we moved again, our walls were beginning to fall apart. I resolved that if I ever needed another wall I’d hire someone with better credentials.

Enter Eugene mason Alan Ash. Our new yard has poor soil and a high water table, and we have used lots of river rocks to retain shallow berms of better soil for planting. So when I decided that the sloping change of grade in the middle of our garden was a waste of potential space for vegetables, I tried to imagine a retaining wall that would fit the river rock theme better than the typical quarried basalt. Ash has been in the masonry business for 30 years. He builds walls in a great variety of styles and materials, but he specializes in dry-stacked walls. (He is a member of the Dry Stone Walling Association of Great Britain.) When I saw wall he built incorporating some more or less rounded boulders, I got in touch with him.

Ash was immediately fired up by the river rock idea. As it happens, he had recently collaborated on a stone planter bed constructed with flattish river rocks in an ancient Welsh style that was new to him, and he was keen to build another clawdd wall. Traditionally, clawdd (pronounced, very approximately, clowth) is a free-standing field boundary, consisting of an earth bank strengthened by stacked rocks embedded in both sides. But walls in the clawdd style are also found as retaining walls, like the one he built for me.

Clawdd walls are generally made with the naturally occurring stones of a given  locality, set vertically in more or less horizontal courses. The stones of each layer are wedged into the course below, and soil is packed in behind. The bulk of the rock is embedded in the bank. According to Sean Adcock, head of the North Wales Branch of the Dry Stone Walling Association, “The length of stone set into the bank … is always more than the height left showing on the visible face.”

In North Wales these walls are often built out of rounded glacial fieldstone, which is somewhat similar to river rock. It can be difficult to fit such stones in a flat-laid wall, but they are fine for a technique which sets them vertically. In Eugene, the local Willamette River rock proved to be an ideal material, Ash says. Walls like mine are economical of material and space, since they are only one rock thick, and the rock hasn’t traveled thousands of miles. Alan is impressed by the finished wall’s strength and appreciates the fact that it uses a readily available local material which is difficult to use in a conventionally built dry stone wall.

Ash adds that clawdd walls, where they form field boundaries in an agricultural landscape, play an important role as mini nature reserves. Plants grow in the spaces between the stones, and the earth core can be a haven for small mammals, reptiles, amphibians and invertebrates — more so than a regular dry stone wall, he says. Ash is anxious to see my wall planted, a job I plan to undertake this fall and winter. He points out that plants are sure to grow in the crevices, so I might as well try to choose what they are!  My English sister thinks the wildlife most likely to make a home in my wall are snails. And will I be able to keep the weeds out? We’ll see.