Garden Spaces: Create a Rock Wall Garden

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Click on the IMAGE GALLERY, then NEXT, for the planting key.
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Click on the IMAGE GALLERY, then NEXT, for the planting key.

• Design Plans: Grow These Rock Wall Garden Herbs

Any gardener lucky enough to have a rock wall in a sunny location has a great spot to tuck in a whole garden full of drought-tolerant plants to creep, crawl and cascade over and under and between the rocks. Many of the herbs that hail from the Mediterranean region, with its rocky terrain and dry climate, appreciate the excellent drainage that a rock wall delivers.

The thymes, in particular, love scrambling over rock and working their little roots into every crevice–they’re the ultimate rock-wall plants. Try as many different types as you have room for, including lemon thymes and the tiny-leaved woolly thyme. Prostrate rosemary and oregano are also good candidates, and chives can add their pink pop when they bloom in early spring. The lovely dianthus can be tucked into rock pockets. Avoid plants that require moist conditions or those that are too rampant in their growth habits, such as the mints.

Other logical candidates for a rock-wall environment, at least in dry climates, are the plants known generally as succulents. Watch out, because once the gardener becomes smitten, these are addictive. Gardeners in mild climates have more choices, but there are some hardier varieties to be found as well, if you hunt for them.

{TIP: Keep a collection of aloes and other succulents in the driest edges of the rock wall garden.}

I find the succulents intriguing; they bring out the collector in me, and I like the contrast in form to the herbs and flowers that can grow here among the rocks. Succulents are among the most drought-tolerant of all plants, so plant them toward the top of wall, and perhaps on the edges where they’re not within range of any automatic sprinklers. Then forget them, as they thrive on neglect.

If the aloe or other succulents aren’t hardy in your area, grow them in pots to sit on the edge or cluster at the base of the wall, and move them indoors for winter or be prepared to protect them through the winter. Or grow them as annuals, replacing them in spring or trying new varieties to find favorites.

Build a Rock Wall

If you don’t have a rock wall, you might want to think about how and where you can build one. Investigate rock and stone quarries or vendors in your region, and talk to the professionals. A stack of flat or nearly flat rocks, preferably a native rock that blends into the garden environment, is a good way to berm a raised bed, which creates ideal conditions for herbs, succulents, vegetables, roses and many other garden plants. A rock wall can also be used to level off a plot that is on a slant–or when you want to create some elevation, perhaps surrounding a patio area to create some privacy and separation from neighbors.

Building a rock wall takes a lot of muscle and sweat, no question, and a big investment of time and money, but the gardener willing to take it on can ensure there are plenty of pockets of space where dirt and plants can be tucked in. Whether your wall is a foot high or head-high, it’s essential that it be rock-solid. Start by digging down a few inches to spread a foundation layer of coarse sand or gravel. A double row of overlapping flat rocks, stacked so that the wall steps backward just slightly, will ensure stability. As you build, add layers of dirt and leave spaces for planting, fairly evenly distributed over the wall; add good dirt mixed with compost to fill in all the planting pockets and stabilize the rock.

When you plant it, start with the smallest transplants you can find (or germinate them yourself from seed or cutting), as they are the easiest to wedge into the small spaces between rocks, using a trowel or knife. After you’ve tucked in the plants and added as much dirt as you can in tight spaces, add some water to the soil to make a thick slurry to pour in to cover the roots and fill in any air pockets.

{TIP: Self-seeding plants, like chives, can be an advantage for a rock wall, getting its seed into tight places more easily than the gardener can.}

Combine plants that cascade down from the top (like prostrate rosemary) with plants at the base that grow upright, such as lavender, all interspersed with tidy clumps of dianthus with its brilliant color and soft mounds of santolina.

How to Water & Maintain

As with all gardens, give these new little plants time to get established and growing before backing off on the watering schedule. Water gently to avoid washing away any of the precious dirt and compost you’ve incorporated into the wall; eventually all the dirt will settle in and pack down and not be constantly threatening to fall out. And keep a careful eye on any succulents to ensure they aren’t overwatered.

Once established, this is a carefree, undemanding garden space. A network of roots will eventually spread through the dirt and rock to make it firm and stable. Keep the wall weeded well until the plants get big enough to crowd out the weeds on their own. It won’t need much fertilizing.

Whether you’ve created or inherited your rock wall, learn about it as you go. Remember that rock can absorb and retain warmth and contribute to protected microclimates in your yard that can grow more tender plants than in other, more exposed locations; light-colored rock reflects light back into the plants.

Before you know it, your garden will be a perfect spot to plop down in a chair for a cup of tea.

Kathleen Halloran writes and gardens in Texas.

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