Cabernet Stone Terracing
It seems like whenever clients call us about terracing a slope on their property, the slope is actually too steep to terrace with dry stone. The slope usually turns out to be steeper than 1:1, one foot of vertical for every foot of horizontal (a quick way I estimate is to stand on the slope and measure or eyeball the distance straight out from my shoulder, my shoulder is five feet high, so if the distance to the slope is five feet then the ratio would be 1:1, ten feet would be 1:2, fifteen feet would be 1:3, and so on; if the distance to my shoulder is less than five feet the slope is too steep), and that math just doesn’t lend itself well to dry stone retaining walls, which rely on their thickness and weight to hold back the weigh of the slopes they retain. For instance, a two foot high wall needs to be a foot thick at the top, so if your wall rises two feet on a 1:1 slope, it only creates two horizontal feet and one of those feet will be taken up by the wall; your net gain is only one foot of flat planting space. It’s rarely worth the money or effort, so we usually end up building a wall at the base of the slope and then planting the rest of it with plants that thrive on slopes.
This little planting in San Francisco is the first time we’ve actually terraced a slope, though, in reality, it barely qualifies as terracing; it’s more like one wall split into two shorter walls. We could have built it as a single two and half foot high wall. But because the whole planting is at eye level on top of a thick concrete retaining wall, we didn’t want to be adding another giant wall to further loom over people. So we split the wall into two separate walls and then further softened the impact of the stone by setting the lower wall back from the concrete to create space for plants.
For the plants, we chose ones that are soft textured, drought-tolerant and mostly native to coastal California. A few of them are considered rock garden plants, a somewhat subjective term, but typically rock garden plants like sandy or gravelly soil, tolerate or enjoy reflected heat from stone, have a smaller size, and are best appreciated up close and at eye level, all elements of this planting. And then a few of the plants like the Myrica and the Phormium are standard landscaping plants for San Francisco. A photo of the whole little planting and the plantlist is below.
Agonis flexuosa “After Dark” (Peppermint Tree)
Stipa arundinacea (New Zealand Wind Grass)
Eriogonum grande var. rubescens (Red Buckwheat)
Arctostaphylos uva-ursi “Wood’s Compact” (Manzanita groundcover)
Brodiea laxa “Corrina”
Phormium (Purple New Zealnd Flax)
Myrica californica (Pacific Wax Myrtle)
Ceanothus foliosus “Berryhill”
Achillea millefolium “Cassis” (Yarrow)
Erysimum concinnum (Pt. Reyes Wallflower)
Erysimum menziesii (Menzie’s Wallflower)
Narcissus “Stratosphere” and “Hillstar” (Daffodil)
Should be nice when everything grows in.
— Update —
I passed by this garden when the Frying Pans (Eschscholzia lobbii) were blooming on top of the wall. Also, some regular California Poppies (Eschscholzia californica) had come up in the planting as a legacy of what was growing there before. There won’t be space for either type of poppy when the planting fills in, but it sure is nice to have the early color.
This entry was posted on Sunday, January 18th, 2009 at 10:29 pm and is filed under stone, walls. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.