The Rambling Rose: Walks with a Master Gardener
Terracing, with Cynthia Nations
By Susan Kornfeld
To terrace or not to terrace. That is the question facing gardeners blessed with a slope. That was the question I set out to explore with UC Master Gardener Cynthia Nations on a drizzly morning in May. I wanted to see the terrace system she’d installed a year ago and then take a wander around the neighborhood to look at other slopes and other solutions. Cynthia’s particular garden blessing came in the form of an average-size front yard with a steep slope. She wanted more options than “crawl up and rappel down.” Nor did she want to blow her budget on just one part of the property.
“The decision was easy enough,” she said. “Terracing is perfect for steep slopes. It keeps the rainwater on the ground rather than allowing it to run off down the hill, and it gives me and my knee replacement easy access to the plants. The only question was how many levels I needed.”
Using stacked and interlocking blocks, Cynthia created a green amphitheatre of five terraces stepping up from the front patio to street level. Each row of plants complements the one above and provides enough horizontal repetition to create a neoclassic look. Broad stairs along the side invite visitors to enter the terraces. And because her plantings are all drought tolerant, she doesn’t need an irrigation system to pump water uphill. After a couple months of hand watering to get her terrace plants established, Cynthia’s grasses and flowering plants have thrived with no irrigation at all.
Cynthia lives near Deer Creek in upper El Granada — perfect ambling grounds for the Rambling Rose. We’d hoped for more than the slight drizzle we experienced, but it was May and we were happy for what the skies gave. We set out and discovered that the first house, right next door, offered a lovely example of a non-terraced slope.
Imagine an easy stroll downhill through a meadow to go home. Delightful!
Longer but less steep than Cynthia’s, this slope is anchored midway by a tall pine. Dymondia, iceplant, and other groundcovers tumble downslope, punctuated by various shrubs, all of their roots interlocking to knit the soil together and prevent water runoff and soil erosion.
“That’s a great strategy,” Cynthia pointed out. “With the tree, the shrubs and the ground cover, the rain hits the larger plants first, then the smaller, and then just eases into the soil.”
Broad, timbered steps, filled with stream gravel and errant dymondia, provide a mini-terraced walkway down to the house. Where the slope steepened a bit the walkway gave a gentle turn, winding charmingly to the front door. Imagine an easy stroll downhill through a meadow to go home. Delightful!
We wandered over to Deer Creek, just a couple of blocks away, to see how much water was flowing. Along the way we passed a wide variety of terrace and retaining structures ranging from one small and messy fieldstone wall (which I could imagine myself happily piling together and then cramming every nook and cranny with little succulents) to a couple of more utilitarian block walls. The latter, we thought, could be softened by adding some trailing plants or vines; lobelia, maybe, or clock vine. A cement-covered slope with ivy peering out of holes punched into it was one landscaper’s solution to reduce weeds and erosion, but such a surface also prevents rainwater absorption and exacerbates runoff. Permeable surfaces help our seasonal rains percolate into the soil and replenish the water table.
…note how the tallest plants are uppermost. That’s where their roots can do the most good.
There were plenty of examples to appreciate, both in a rustic, cottage-garden style and in the clean lines of more contemporary approaches. One homeowner, for example, had installed three levels upslope from a stamped-concrete driveway. Two levels were terraced with split-face blocks, and the third with a beautifully crafted dry stone wall.
The center level featured a small patio with bermed plantings on either end, flowers and greenery spilling over and softening the rock. “That completely works for me,” Cynthia said. “Everything is within easy reach and that patio is a perfect place to sit and chat. Plus, they didn’t mortar the flagstones. Otherwise water would just run off it.”
Down the street, Cynthia showed me a corner home that was built just last year. She particularly admired their landscaped verge that not only sloped downhill along the road but sloped down to the road itself. “Look how they placed the boulders in between and at the edges of the plantings,” she said. “That helps hold the soil until the plants fill in, and it also adds richness and a real solidity to the bed. And note how the tallest plants are uppermost. That’s where their roots can do the most good.”
I loved the fragrance: lavender and ceanothus mingled their spicy aromas with the crisp scent of rain-drenched ornamental grasses. Tall ruby-hued penstemons glowed against the deep and lime greens of the foliage plants. Another charming stairway lined with flowers and edged with thyme and field boulders led up to a tousle of poppies near the front door.
It’s a steep slope from street to patio and every inch seems to have some little treasure, some interesting plant cunningly emerging from around a driftwood hobgoblin or a pile of collected stones.
As we approached the creek we noticed that between the stacked slate walls and groomed lawns edged with equally groomed bark mulch, there were lots awash in crown vetch and towering geraniums. Horsetail made an occasional escape out of boggy depressions, and masses of nasturtiums bloomed in orange felicity along several stretches of stream bank, decorating those slopes quite prettily. “I don’t think we properly appreciate nasturtiums,” I remarked to Cynthia. “It’s such a friendly, forgiving, un-needy plant.”
“And you can eat it,” she replied. We passed without comment the stinging nettles, likewise edible if you can manage to pick it, and the jubata grass.
One particularly attractive arrangement along the creek had a cut-stone retaining wall along part of the embankment. There was a pretty bit of grass below it and a hydrangea just coming into flower setting off the earth tones of the wall. With the water table so high in this area, Cynthia doubted if either grass or hydrangea needed any irrigation. Closer to the creek, the homeowner had planted a large monkey flower bush with rushes interspersed with forget-me-nots and daisies. We agreed the small retaining wall not only gave structural support to the landscape but focused the attention on the flowers and water. Art and arrangement — and a great helping hand from Mother Nature herself.
She started with a chainsaw and an old telephone pole someone said she could have.
Every excursion needs a bit of magic, and we found ours at the end of San Juan Avenue where the last home tucks into the hill above the creek. It’s a steep slope from street to patio and every inch seems to have some little treasure, some interesting plant cunningly emerging from around a driftwood hobgoblin or a pile of collected stones. The owner, a very, very nice woman named Tina, saw us poking about and invited us to explore. As we made our little discoveries, Tina told us how she has coaxed and assembled the luxuriant whimsy of her slope garden over the last twenty-five years.
She started with a chainsaw and an old telephone pole someone said she could have. That provided steps down the steepest part of the slope. A friend helped her scavenge slate flagstones from a landslide near Auburn, and these she used for a patio and steps in a less steep area. Then she covered the slope in horse manure, stamped down enough flat spaces to walk on, and half buried whatever bits of other timber, rocks or other solid objects she could carry home. Friends brought over foxglove, borage, alyssum, aeoniums, and euphorbias. Ferns arrived voluntarily. Clumps of lilies likewise appeared. She eventually added spider plants for the mass of their roots. Everything jumbles together down to and around an anchoring pine. A woodland cascade.
Baby tears and pine needles now litter the steps that Cynthia admired but considers “too steep for comfortable gardening — or even walking.” She worries, too, that the slope is not sufficiently guarded against an intense El Niño winter, “but, heck, it’s obviously weathered at least one El Niño to say nothing of an earthquake.”
Tina walked us up back up to the road when we left. We noticed the lovely blue-green faces of sempervivum — Hen and Chicks — peeking out from amid the branches of some prostrate junipers. “I had gophers up here,” she explained. “I just plug stuff into gopher holes as they turn up.” And that is a wise gardener.
Cynthia’s Tips for the Slopes
- Don’t till your slope! Tilling causes a loss of soil structure and might cause the soil to slide away.
- Cover your slope with a mix of groundcovers, shrubs, trees, and perennials. Use fast-growing annuals that can be removed once your perennials and shrubs fill in.
- Use informal groupings of boulders to anchor portions of the soil and add interest.
- Wide, curving stairways are easier to traverse than those that are straight and steep.
- Narrow terraces and repeating plantings create a modern look; trailing plants and casual, jumbled groupings look rustic and romantic.
- Use a rock swale within a terrace so that rainwater percolates slowly into the earth and any excess water flows away parallel to the slope.
- Water with drip or soaker hose to minimize runoff.
- Provide drainage and diversion for any runoff water. Ideally, divert to other planting areas downslope.
- A series of small terrace walls is better at holding water than a massive retaining wall — and usually more attractive.
- Use mulch where soil isn’t covered by plants or boulders. Shredded redwood stays put better on a steep slope than large bark.
- Place the most drought tolerant plants at the top, the least at the bottom.
- Plants for coastal garden slopes: Ceanothus, cistus (rock rose), juniper (a prostrate or creeping variety), rosemary, echium (Pride of Madeira), coffee berry, California buckwheat, coyote brush, various salvias and sages. Attractive volunteers should always be encouraged.
About Cynthia Nations
A retired educator and consultant, and now a UC Master Gardener, Cynthia moved to El Granada in 2014 where she is close to her two grown daughters. She specializes in succulents and — after her latest project — terracing.
About Susan Kornfeld
The Rambling Rose, known to her gardening clients as The Cottage Gardener, Susan has been gardening professionally in San Mateo County since 2012 after a five-year stint in New Zealand. She just earned certification as a UC Master Gardener and is thrilled to be a master of anything.
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