Lavender bursts from the crevices of a 600-foot-long stone wall at Powell Gardens in Kansas City, Missouri, filling the air with intoxicating fragrance. Hens and chicks add exotic punch to this vertical garden, while thymes lend delicate beauty. But don’t let their looks deceive you. These plants are tough!
When planning this living wall, director of horticulture Alan Branhagen selected more than 250 different plants for their beauty and adaptability. Home gardeners could scale down this project easily and use herbs exclusively, he says.
Any stone wall made without mortar could be planted this way, whether a freestanding fence, retaining wall or raised-bed border. If you don’t have a wall already, you can build one—it isn’t that difficult (see “Create an Herbal Rock Wall”). Either way, if you plan and plant well, your herb wall will be a perennial source of beauty and virtually carefree once established.
Branhagen offers these expert tips for making your own herbal rock wall.
1. Rock solid. If you’re building a new wall, select or buy rocks that are hard, relatively flat and suited to the surrounding landscape. The Powell wall, for instance, features gray and golden-brown limestone, its warmer tones serving as a counterpoint to a winding concrete path. A garden supply center or stone quarry can help you choose the best rock for your site and project.
2. Look for plants that like hot, dry conditions. Drought-tolerant lavender and thyme are both excellent choices for a rock wall. Thymes of nearly any variety are especially attractive in a stone wall; their delicate runners cascade over the stones “like little waterfalls,” says Branhagen. For a taste of something different, try lemon or caraway thymes.
Avoid herbs that tend to run wild or that require a moist environment. “Mints are way too big and rambunctious,” he says.
3. Consider the big picture. When creating your plant list, consider how the plants will look together, as well as how they will fit with your overall landscape. Think about their blooms, flavor, fragrance and usefulness. Some plants are valuable for their color alone. Autumn sage (Salvia greggii), for instance, will contribute splashes of red all summer long, if deadheaded regularly.
A variety of plant shapes adds interest: Choose herbs that creep, cascade and mound. If possible, position contrasting plants near one another, advises Branhagen. Plant a spiky rosemary next to a soft-textured santolina, for instance, or try silvery artemisia next to red and chartreuse hens and chicks.
4. Top it off with style. For the top of the wall, you might follow Powell’s lead by planting a mix of cascading plants, such as prostrate rosemary ‘Severn Sea’ and trailing roses with sprawling catmints. Anchor the base of the wall with upright plants, such as yarrow, feverfew or anise hyssop. “Right plant, right place is always our theme,” Branhagen says.
Although Powell primarily features perennials, you could experiment with annuals, such as basil and cilantro, says senior grower Mark Gawron. Many herbs are naturally short-lived, both horticulturists note. So be flexible—and expect to refresh your wall plantings periodically. Each time you replant is an opportunity to renew the look of your wall and your landscape.
5. Easy does it. Once established, your vertical garden should be a breeze to manage. Don’t fertilize and don’t over water, cautions Branhagen. Harvest throughout the season—to enjoy, to prolong bloom and to keep plants tidy. In the spring, clip back any winter kill. In the fall, take cuttings of plants you think might not survive the winter, root them indoors, then plant the starts back in the wall when weather warms in spring.
12 Herbal Rock Stars
||(Lavandula angustifolia and hybrids): Zones 5/6-10. Choose compact varieties, such as 12-inch ‘Munstead’. ‘Buena Vista’ offers superb fragrance and bi-colored flowers on 18- to 24-inch plants and blooms twice per season in many locations.
||(Thymus spp.): Zones 4-9. Most thymes grow well on a rock wall, but ‘Pink Chintz’ and red creeping thyme are spectacular. For yellow-flecked lemon-scented foliage, try ‘Doone Valley’.
||(Satureja montana): Zones 6-9. This spicy herb has proved a pleasant surprise at Powell Gardens, contributing a touch of green throughout the winter. The 8-inch plants are showered with white flowers in midsummer.
||(Santolina spp.): Zones 6-10. Both gray (S. chamaecyparissus) and green (S. rosmarinifolia) santolina provide soft aromatic foliage and yellow button flowers. Gray santolina reaches 16 inches; green grows to about
||(Rosmarinus officinalis): Zones 8-11. Arching or prostrate cultivars, such as ‘Severn Sea’, ‘Irene’ and ‘Santa Barbara’ are ideal for cascading over the top of a wall. ‘Severn Sea’ is hardier than most (to Zone 7). In Zones 7 and northward, grow rosemary as an annual.
||(Salvia spp.): Zones 5-11. The culinary sage ‘Berggarten’, with its dense, compact habit, has performed well in Powell’s Zone-6 living wall. Tri-color and purple sages have proven less hardy.
||(Origanum spp.): Zones 5-9. Hybrid ‘Amethyst Falls’, with huge sprays of chartreuse bracts and purple flowers on 15-inch plants, is an eye-catcher. ‘Herrenhausen’ has cerise flowers and purple-green leaves on 24-inch plants.
|Hens and chicks
||(Sempervivum tectorum): Zones 4-9. These hardy succulent perennials feature intricate low-growing rosettes and thick, fleshy leaves.
|| (Agastache foeniculum): Zones 6-10. The fragrant leaves of this 32-inch perennial can be used in teas as well as in fish and chicken dishes. Its mauve flower spikes make pretty bouquets. ‘Golden Jubilee’ grows just 20 inches tall.
||(Nepeta spp.): Zones 4-9. Most types produce bright blue flower spikes on sprawling 16- to 30-inch plants. The fragrant gray-green leaves make a tasty tea. Lemon catnip (N. cataria ‘Citriodora’) has white flowers.
||(Artemisia spp.): Zones 4-9. The fragrant, silvery foliage makes a handsome addition to fresh or dried arrangements. ‘Silver Mound’ and other low-growing types are good choices for walls.
||(Achillea tomentosa): Zones 3-8. Planted at the base of the wall, this drought-resistant beauty makes a graceful transition to lawn areas. Compact 6- to 12-inch plants have aromatic leaves and lacy golden blooms.
— Freelance writer Carol Crupper and photographer Diane Guthrie grow herbs in their gardens in Lawrence, Kansas.