Hot Sunny Slopes and the Plants That Hold ‘Em:
Five Groundcovers That are Deep-rooted and Firewise
'Dana Point' Buckwheat center, with 'Pigeon Point' Coyote Brush in Foreground (left) © 2010 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.
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' Sage, Washington Park, Pasadena, © 2008 Orchid Black
Mrs. Beard Sage and Bee’s Bliss Sage, Salvia sonomensis hybrids
Salvia 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 6 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 sometimes called ‘Gracias,’ is a gray spreader, with purple-blue flowers. Both plants attract hummingbirds and butterflies.
'Bee's Bliss' Sage, Rancho Santa Ana Botanic Garden, © 2006 Orchid Black
'Pigeon Point' Coyote Brush © 2010 Orchid Black
‘Pigeon Point’ Coyote Brush, Baccharis pilularis
This reliable, neighbor-friendly plant is a medium green year-round, grows in a beautifully even habit less than 18” tall, and can get more than 6 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’ is a little higher in the center, up to 3 feet.
'Dana Point' California Buckwheat just coming into bloom, © 2010 Orchid Black
‘Dana Point’ California Buckwheat and other cultivars, Eriogonum fasciulatum
These plants form tidy dome shapes that are beautiful for their sculptural quality, but also stay fairly low atless than 3’ in the center. They have beautiful creamy flowers in summer that fade to rust. Good groundcover cultivars include ‘Bruce Dickinson,’ ‘Theodore Payne,’ and ‘Warriner Lytle.’ California Buckwheat is an important larval and nectary plant for many native butterflies.
'John Dourley' Manzanita, Rancho Santa Ana Botanic Garden, © 2006 Orchid Black
‘John Dourley’ Manzanita, Arctostaphylos sp.
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 5’ in the center if supported. The oldest one I have seen is about 25 years old on a south-facing slope in Altadena. It is 9 to 10 feet across, and 4 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.