Coping with Slopes
Full sun to partial shade
Average to dry soil
Slopes offer both interesting challenges and exciting opportunities when it comes to gardening. They’re typically drier than nearby flat areas, because rainwater tends to run off before it has a chance to soak into the soil, especially on steep slopes. When water runs quickly down a slope, it’s also likely to pick up loose soil as it flows, carving channels into the ground and dumping eroded topsoil onto the lawn or paved area at the bottom. But on the plus side, slopes give you a chance to experiment with beautiful perennials that thrive in dry, sunny sites. Slopes also display plants exceptionally well, allowing stems and leaves to trail gracefully and showing off nodding or short-stemmed blooms beautifully.
The Garden Plan
Shopping List
1 Mexican feather grass
Stipa tenuissima
4 plants
Zones 6–9
Alternates: Another 1- to 2-foot-tall ornamental grass that can tolerate dry soil, such as prairie dropseed (Sporobolus heterolepis) [4 plants] or ‘Piglet’ fountain grass (Pennisetum alopecuroides) [4 plants]
Mexican feather grass (Stipa tenuissima)
2 ‘Oranges and Lemons’ blanket flower
Gaillardia × grandiflora
2 plants
Zones 5–9
Alternates: Another blanket flower or other 1- to 2-foot-tall, orange- or yellow-flowered, mounded or spreading perennial that can tolerate dry soil, such as ‘Sienna Sunset’ or another coreopsis (Coreopsis) [2 plants] or ‘Tuscan Sun’ false sunflower (Heliopsis helianthoides) [2 plants]
‘Oranges and Lemons’ blanket flower (Gaillardia × grandiflora)
3 ‘Big Ears’ lamb’s ears
Stachys byzantina
2 plants
Zones 4–8
Alternates: Another 1- to 2-foot-tall, silver- or blue-leaved, mounded or spreading perennial that can tolerate dry soil, such as ‘Firewitch’ dianthus (Dianthus) [2 plants] or October daphne (Sedum sieboldii) [2 plants]
‘Big Ears’ lamb’s ears (Stachys byzantina)
4 ‘Walker’s Low’ catmint
Nepeta
2 plants
Zones 4–8
Alternates: Another 1- to 2-foot-tall catmint or other mounded or spreading, blue-, purple-, or pink-flowered perennial that can tolerate dry soil, such as a lavender (Lavandula) [2 plants] or an ornamental oregano (Origanum) [2 plants]
‘Walker’s Low’ catmint (Nepeta)
5 ‘Angelina’ sedum
Sedum rupestre
2 plants
Zones 3–8
Alternates: Another creeping sedum or other 4- to 12-inch-tall, mounded or spreading perennial that can tolerate dry soil, such as moss phlox (Phlox subulata) [2 plants] or ‘Snow Flurry’ heath aster (Aster ericoides) [2 plants]
‘Angelina’ sedum (Sedum rupestre)
Planting Plan
Season by Season
Spring: There’s lots of early color and texture in this garden, starting with the foliage of ‘Angelina’ sedum. Mexican feather grass joins in early, too, quickly forming fountain-shaped clumps of hairlike, bright green leaves and bearing wispy greenish flowers by late spring. The hairy foliage of ‘Oranges and Lemons’ blanket flower isn’t especially showy now, but the fuzzy, bright silver leaves of ‘Big Ears’ lamb’s ears are quite attractive, as are the dense, gray-green mounds of ‘Walker’s Low’ catmint. The catmint is also in bloom by late spring, with loose spikes of purple-blue flowers over the small, aromatic leaves.
In early to mid spring, cut the Mexican feather grass back to about 4 inches above the ground, and cut the blanket flower, lamb’s ears, and catmint back to 2 to 3 inches above the ground. The sedum generally doesn’t need pruning, unless you want to trim off any winter-damaged bits. This is also a fine time to divide any of the perennials that were starting to outgrow their space last year. Finish up by spreading a fresh layer of organic mulch around the plants.
Summer: Through the summer, the greenish flowers of Mexican feather grass gradually ripen to golden brown and then tan. ‘Oranges and Lemons’ blanket flower begins blooming in early to midsummer and continues for months, with soft orange-and-yellow, daisy-form flowers. ‘Big Ears’ lamb’s ears occasionally sends up fuzzy stalks with small pinkish flowers, but they’re not very showy; the gray-green leaves are its main summer feature. ‘Walker’s Low’ catmint is in peak bloom in early summer, with a few new flowers possible in midsummer. ‘Angelina’ sedum produces yellow flowers in summer, but they’re hardly noticeable against the bright yellow foliage.
Clip off the dead flowers of the blanket flowers individually through the summer or shear the whole clump back to about 6 inches in late summer. If the lamb’s ears produce any flowering stems, cut them off at the base. In humid summers, the lamb’s ears leaves may look tattered or start to rot; if that happens, shear the whole plant back to about 2 inches to remove all the leaves so fresh foliage can emerge. Cut back the catmint clumps by one-half to two-thirds in midsummer to get bushy new growth and promote rebloom later in the season. Clip off the dead flowers of the sedum to tidy the plants and prevent self-sowing, if desired.
Fall and Winter: Mexican feather grass’s foliage continues to look good through fall, gradually turning blonde-tan as it dries and staying in place for the winter. ‘Oranges and Lemons’ blanket flower keeps flowering through fall, and even into early winter in mild areas. ‘Walker’s Low’ catmint, too, often reblooms through fall, and its foliage remains into early winter, or even longer. The leaves of ‘Big Ears’ lamb’s ears stick around for most or all of the winter. ‘Angelina’ sedum holds its leaves all through the winter, typically taking on a rich orangey color.
It’s best to leave the plant tops in place for the winter to protect the soil from erosion from winter rains, so there are no late-season tasks to take care of.
Digging Deeper
- This pair of mini-borders is designed to edge a short flight of steps. To flank a higher set of steps, repeat each border end to end as many times as needed. To extend the planting across a slope rather than up it, set the two parts side by side and repeat them as needed to cover the area.
- A perennial garden is a pretty solution for a relatively short, gentle slope, and it’s certainly more interesting than straggly, hard-to-mow lawn grass. If there’s more than about 3 feet from the bottom to the top of the slope, though, consider installing a low wall (6 to 12 inches tall) across the site. Breaking up one steep slope into two shorter, gentler slopes slows down water runoff and prevents erosion, providing better growing conditions for the perennials. A well-built wall also serves as an access path, giving you a place to walk or sit when you’re planting, weeding, or doing other maintenance.
- When you’re choosing plants for sloping sites, stick with those that are about 1 foot tall or shorter, because taller stems are more likely to sprawl and look messy. Perennials that form low, spreading mounds or ground-hugging carpets do the best job in preventing soil erosion, especially once they’re settled in and mingling to form a solid carpet, with no mulch or bare soil visible.