Hot Sunny Slopes and the Plants That Hold ‘Em
By Orchid Black
Slopes and hillsides can be difficult spaces to garden, so much so that seedswoman and author Judith Larner Lowry, in her book, Gardening with A Wild Heart, says that one of the most common calls her business receives starts with, “I have this slope behind my house…” Plants for slopes must perform many functions: control erosion, hold the slope, be drought-tolerant, and, since slopes are often in fire-risk areas, be firewise. Happily, there are many plants in the native palette which meet these needs.
Five groundcovers that are deep-rooted and firewise
Many of these plants are coastal forms of native shrubs. Wind pressure on the coast has allowed plants to evolve lower, wider versions of their inland cousins which are ideal groundcovers. These plants are generally around five to six feet wide or more, but only one to three feet high. Manzanita ‘John Dourley’ is the tallest shrub mentioned in this article, at more than four feet high in the center. They hug slopes with a blanket of foliage, and because they are shrubs, they have deep roots that hold the slope. As groundcovers, low shrubs don’t develop flame height, making them firewise even in high winds. Each of these plants can also be used in wider parkways, with allowance made for separate walkways, as they are not tolerant of much foot traffic.
Mrs. Beard creeping sage and Bee’s Bliss sage
Mrs. Beard creeping sage (Salvia sonomensis ‘Mrs. Beard’) is my all-time favorite slope-holding plant. It was the only plant that gave some coverage within a year on the difficult, steep south-facing slope at Washington Park. It is about a foot in height, with a fast spread to six feet. In later years, some branches often need to be taken off at the base. Its foliage is bright spring green, with pale blue flower spikes appearing in early spring. Its cousin Bees Bliss sage (Salvia x ‘Bee’s Bliss’), also a Sonoma sage (Salvia sonomensis) hybrid, is a gray spreader with purple-blue flowers. Both plants attract hummingbirds and butterflies.
Pigeon Point coyote brush
Pigeon Point coyote brush (Baccharis pilularis ssp. pilularis ‘Pigeon Point’) is a reliable, neighbor-friendly plant. It is a medium green year-round, grows in a beautifully even habit less than eighteen inches tall, and can get more than six feet wide. I always wonder why this robust plant isn’t used on freeway slopes instead of acacia. I usually tell clients that this plant is a member of the chorus line; it is not a star. It is an ideal slope holder with deep roots, and a beautiful backdrop to showier plants. Another coyote brush, Twin Peaks No. 2 dwarf coyote brush (Baccharis pilularis ‘Twin Peaks No. 2’) is a little higher in the center, up to three feet.
Dana Point buckwheat and other cultivars
Dana Point buckwheat (Eriogonum fasciculatum ‘Dana Point’) forms a tidy dome shape that is beautiful for its sculptural quality, but also stays fairly low at less than three feet in the center. It has beautiful creamy flowers in summer that fade to rust. Good groundcover cultivars include Bruce Dickinson California buckwheat (Eriogonum fasciculatum ‘Bruce Dickinson’), Theodore Payne California buckwheat (Eriogonum fasciculatum ‘Theodore Payne’), and Warriner Lytle buckwheat (Eriogonum fasciculatum ‘Warriner Lytle’). California buckwheat is an important larval and nectar plant for many native butterflies.
John Dourley manzanita
John Dourley manzanita (Arctostaphylos ‘John Dourley’) has a beautiful grayish foliage with the classic red stems of manzanita, and the new foliage is tipped with a coppery bronze, forming a lovely contrast to your average green. It has light pink urn-shaped flowers followed by berries in an old-rose color. This is the biggest of these groundcovers, and can get up to five feet in the center if supported. The oldest one I have seen is about twenty-five years old on a south-facing slope in Altadena. It is nine to ten feet across, and four feet high.
Any of these plants look great in massed plantings on a sunny slope. They will need water once a week to get established, but can live on less water once established. Slopes should be weed-free before planting, and should have mulch between the plants to suppress weeds. Because the plants have such a large diameter, it is helpful to use a tape measure when planting to make sure they have room to grow.
These great groundcovers can turn a dry, steep problem area into a beautiful garden setting for you to enjoy year-round and a sunny habitat for birds and butterflies.
Orchid Black is a garden designer and owner of Native Sanctuary (formerly Pitcher Sage Design), which offers native plant consulting, habitat creation, and sustainable design services to the greater Los Angeles area. She has served on the Board of the CNPS, and served as the Chapter Council Chair. Orchid also writes and lectures about native plants, water-saving strategies, and sustainable gardening.