Best Plants and Erosion Controls for Slopes and Hillsides

Updated on May 15, 2018
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Catherine is a California-certified nursery professional. Her interests are birds, insects, integrated pest management, & organic gardening.

Rocks add visual appeal and function to anchor the soil. A variety of sedums offer textural variations.
Rocks add visual appeal and function to anchor the soil. A variety of sedums offer textural variations.

One of the greatest challenges to both the home gardener and the professional landscaper is a steep slope. Wind and water wreak havoc on the topsoil, uniform water penetration is poor with additional run-off, and the thought of clearing weeds makes us want to go back to bed and pull the covers over our heads! Where does one start?

There are a few different options such as building retaining walls, terracing with horizontal paths, laying down erosion control grids, constructing shelf-like basins around trees and shrubs, and selecting deep-rooted groundcovers. They can all work effectively, but each has its own considerations.

First consider the size of the area and the pitch of the slope. You'll also want to take note of any existing trees and shrubs and the boundaries of neighboring properties. These will all figure in to your final decision.

If the area is large and your slope is at least 30%, creating terraces would be good plan for making more level planting, recreation, and seating areas. Another option for a steeply sloped area is a retaining wall, but these work best in a smaller area where the run isn't too long. A wall can be both costly and subject to damage due to shifting earth. If you do put in a retaining wall, it is important to think about how it will affect any existing trees. You'll have to be careful not to damage roots and to not allow the run-off sediment to collect around the trunks. Terraces should be slightly sloped perpendicularly to the hillside to allow for run-off. In areas of heavy rains or poor soil, pipes with drainage holes can be laid along the terraces in gravel runs then stabilized with rock edging. Soaker hoses and drip irrigation allow easy adjustments to the water delivery for each plant. Remember that deeper, infrequent watering is the best approach.

Groundcovers For Sun

clockwise: Lippia repens, Rosmarinus officinalis "Huntington's Carpet", Baccharis pilularis "Pigeon's Point", Myoporum parvifolium
clockwise: Lippia repens, Rosmarinus officinalis "Huntington's Carpet", Baccharis pilularis "Pigeon's Point", Myoporum parvifolium

Planting well-rooted groundcover is the easiest solution. Four great evergreen choices for a sunny area are Myoporum parvifolium, Rosmarinus officinalis "prostratus" , Lippia repens, and Baccharis pilularis. All of these prefer well-draining soils and are tolerant of drier conditions once established.

  • Myoporum parvifolium, a small leathery-leafed member of the myrtle family, blooms in spring with pink or white flowers. It is deeply rooted and has dense overlapping finger-like stems which block out weed growth. It grows to 3"-4" with a 6 ft. spread. This Australian native is also fire retardant and deer resistant, especially the "Putah Creek" variety. It does attract bee activity in April-June. Myoporum typically lasts for 5-6 years.
  • Rosmarinus officinalis "prostratus" is common rosemary in a low-growing and spreading form. It is a hardy Mediterranean native which is well suited to sunny and water-wise gardens and can grow to 1' with a 6-8 ft. spread. It is wonderfully fragrant, can be used for cooking, produces lovely bee-attracting lavender-blue flowers from winter to late spring, and is resistant to both insects and deer. "Huntington's Carpet" is less woody and works especially well for cascading over retaining walls.
  • Baccharis pilularis, commonly referred to as dwarf coyote bush, is a California native which grows 1'-2' high with a 6'-8' spread. It is evergreen and can get along with little water once established. It is long-lived, low maintanence, and deer resistant. The "Pigeon Point" variety is a good one and looks beautiful combined with flowering accents like California poppies and salvias.
  • Lippia repens, also called Phyla nodiflora, is a very low growing evergreen with a dense matting habit. It attracts bees with its pretty clusters of lavendar flowers in spring and fall. This sun loving ground cover is a great alternative to myoporum for those desiring fast growth. It can get a bit aggressive, so for those wishing a tamer version, there is the sterile, non-seeding Kurapia. Although drought tolerant once established, this will do best with supplemental irrigation in hot areas.

Groundcovers For Shade

clockwise:Fragaria chiloensis, Arctostaphylos :Emerald Carpet", Pachysandra terminalis, Satureja douglasii
clockwise:Fragaria chiloensis, Arctostaphylos :Emerald Carpet", Pachysandra terminalis, Satureja douglasii

Groundcovers For Shade:

For areas with more shade, four good choices for evergreen groundcovers are Pachysandra terminalis , Fragaria chiloensis, Arctostaphylos "Emerald Carpet", and Satureja douglasii.

  • Pachysandra terminalis, commonly referred to as "green carpet" or Japanese spurge, can be slow to start but will be vigorously growing by the 3rd year. It grows to 6"- 10" high and spreads by rhizomes. This Asian native is good for erosion control and will grow under trees, including pines. It has insignificant white flowers in Spring, and is not bee attracting.
  • Fragaria chiloensis, beach strawberry, is a California native well-suited to areas of part-sun to shade and well-drained soil. It bears white flowers from spring-summer, produces edible fruit in fall, and has touches of red foliage for year-round interest. It is a must for bird gardens and dappled woodlands. It stays under 1' with a 12"-18" spread and needs moderate water. A similar alternative is the woodland strawberry, Fragaria californica, whose leaves are brighter green and less leathery.
  • Arctostaphylos "Emerald Carpet" is another California native from the manzanita family. This variety requires more water than the "kinnikinnick" spreading manzanita and is more tolerant of part-shade, but it can handle the inland heat. It reaches 1' in height and can spread 6-8' Small white bell-shaped flowers appear in winter-spring, followed by red berries. The bright green foliage and reddish stems are very attractive. Hummingbirds love the flowers!
  • Satureja douglasii also know as yerba buena or Indian mint, is a fragrant, low growing evergreen. It prefers the shade and moisture of its native habitat, the woodland understory of coastal California. It will grow in inland shade with supplemental water. It stays under 6" with a 3' spread, and is non-invasive. It is deer resistant, and produces white flowers in spring.

When clearing an area for planting, it's best to leave a bit of organic debris. Sticks, stones, and bark help fortify the soil against run-off. A good mulch will keep roots cool and suppress weed growth.I prefer coir fiber or shredded redwood which has a more fur-like quality. It stays matted and is less apt to be disturbed by winds and blowers. Although bark and shredded wood are great choices, the breakdown of carbon can rob the soil of valuable nitrogen. Fertilize accordingly.

Create shelf-like basins around trees and shrubs that are planted into the slope and use varying sizes of rocks for stability and attractiveness. Arrange plants for a layered look, using largest in back then balance the visual layout by randomly placing medium shrubs. Fill in with perennial flowers and clusters of bulbs and ground cover. Jute netting can be used to anchor the hillside until the plants have grown in. It will gradually disintegrate. Sometimes birds or squirrels will swipe it for nesting!

Accessibility is often a problem with sloped areas, so I recommend choosing drought tolerant varieties and being careful to not overfertilize. You don't want to encourage weeds. Newly planted trees and shrubs, even those for xeriscape, will still need regular deep water until established. The addition of a michorrizae-based organic fertilizer at the time of planting wil help the plant grow more vigorously since it helps with the uptake of nutrients. California native plants, however, do best without soil additives and fertilizers.

Whatever you choose as your solution, that difficult slope holds the promise of many things. It doesn't have to be a constant source of work. If you tackle it with thought and care, you can eventually sit back, relax and enjoy watching as nature takes over!

___________

Good Water-Wise Plants for Erosion Control and Wildlife

There are so many choices! Cacti and succulents are also water-wise and visually diverse; they, however, are not helpful for erosion control on their own because of shallow roots. This is especially true for ice plant which can slide away like a skin during heavy rains. They do work well when combined with other well-rooted specimens. The overall considerations should be low maintenance and deep rooting unless terracing allows easy access for pruning and clean-up. Weed cloth also helps to reduce frequent clean-up in these hard-to-work areas.

It's always best to take cues from nature, so I think the best approach to a slope or hillside is a combinaton of trees, shrubs, and ground covers. Not only are they more visually appealing, they will attract more birds and wildlife and break the rainfall which reduces erosion.

Australian varieties:

Grevellia- many varieties

Phormium- New Zealand Flax

Westringia- Coast rosemary

Callistemon "Little John"- dwarf bottlebrush

California Natives:

Quercus chrysolepis- Canyon live oak

Aesculus californica- California buckeye

Ceanothus -many varieties

Sambucus- Elderberry

Trichostema lanatum- Wooly blue curls

Ribes sanquineum- Red-flowering currant

Baccharis pilularis- Dwarf coyote bush

Artemesia californica- California sagebrush

Arctostaphylos - manzanita. There are many varieties from small trees to shrubs and groundcover. They have beautiful sculptural shapes,red bark, and white Spring flowers which provide food for hummingbirds.

Salvia- many varieties

Satureya douglasii- yerba buena

Zauschneria- California fuchsia

Miscellaneous (remember to check for your specific areas):

Salix hookerina- Hookers willow

Cornus stolonifea- Red-twig dogwood

Arbutus- madrone

Heteromeles arbutifolia- Toyon

Amelanchier- Serviceberry

Mahonia- Oregon Grape

Berberis- Barberry (deciduous shrub)

Heuchera- Coral Bells

It's easy to to install a French drain for diverting run-off:

Questions & Answers

    © 2011 Catherine Tally

    Comments

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      • cat on a soapbox profile imageAUTHOR

        Catherine Tally 

        7 weeks ago from Los Angeles

        No. Not at the moment. The only way to get it is by the flat. It is expensive, but keep in mind, a little will fill in quickly. Now that it's in demand, suppliers are limited, and price doesn't vary. It's still a good bet even if you work in smaller sections, then plug from your own matured areas.

      • profile image

        Leslie Black 

        7 weeks ago

        Looking for seeds for the Lippia repens/Phyla nodiflora have a large slope and potted plants are pretty expensive for such a large area. Do you know of a source for seeds? Googled it but no joy. Thanks!

      • cat on a soapbox profile imageAUTHOR

        Catherine Tally 

        5 months ago from Los Angeles

        Hello Angelo. I live on the West Coast and am not an expert on choices for your area. It is important to select for the sun or shade exposure of your given spot. Carolina Jessamine, creeping phlox, and some weeping grasses could work for you. I'd check with your local nursery or Master Gardener website for assistance. All the best!

      • profile image

        Angelo 

        5 months ago

        We live in the mountains of North Georgia. We have a concrete retaining wall 20' long at the top of a slope. What would be best to o plant along the retaining wall to establish good roots for erosion control?

      • cat on a soapbox profile imageAUTHOR

        Catherine Tally 

        13 months ago from Los Angeles

        Hi Terri,

        It's hard to make recommendations w/o seeing a site, and not knowing location and sun exposure. From what you've described, it sounds like the French drain option for diverting run-off might be necessary for you. As for lovely creeping thyme, I think it works best for smaller sunny areas. My experience has been that it gets thin and develops bald patches when used as a stand-alone ground cover. Perhaps intermix it with smaller shrubs and well-placed rocks. The lippia and myoporum I've recommended for sunny locations have flowers and are low growing, but a local nursey may be able to further guide you. All the best with your decisions:)

      • profile image

        Terri smith 

        13 months ago

        Hello,

        I have a question about creeping thyme, I would love to put some creeping thyme on a slope up against my house, but I am afraid of the drainage problem, I am afraid that if we disturbed the soil up against our house, we will get water to our back door to our basement, I have the same problem on the other side. It is a really big problem for me to mow these two hillsides, I really love the look of creeping thyme, or if you don't think that creeping thyme would not work there, what would be your expert opinion? But I would love something with color, that has color a long time. Thanks for any advice you can give me, Terri

      • profile image

        Marie farchik 

        18 months ago

        Plants for texas gulf coast

      • profile image

        Power Garden 

        19 months ago

        Great article & hoping that some of the Ca. plants will take in an 8b/9 East coast slope environment.

      • cat on a soapbox profile imageAUTHOR

        Catherine Tally 

        4 years ago from Los Angeles

        Hello Hailey. Thank you for sharing your successful experience with erosion control. The banks near the coastline are some of the most challenging! I appreciate your helpful comments.

        Cat:)

      • Hailey Smith profile image

        Hailey Smith 

        4 years ago from Utah

        Based from my personal experience, the myoporum parvifolium plant and a retaining wall, works the best at preventing erosion. I have a vacation home on the banks of the California Coastline. When we moved in, it was a very steep slope. This is the main reason we got such a great deal on it. Luckily, we studied enough to know what would help keep the home in place, stable and firm.

        http://hydroseedingsocal.com/erosion-control.html

      • profile image

        Candice Harding 

        4 years ago

        Growing up I lived in the high Californian desert. My family learned the hard way how essential erosion control is after heavy (and unexpected) rain washed most of our dirt driveway down the hill and into the backyard. My parents now use a combination of plants and erosion control devices recommended by a contractor to keep the floods out of the yard.

        Candice Harding

        http://www.specialtysupply.com/product-lines/erosi...

      • cat on a soapbox profile imageAUTHOR

        Catherine Tally 

        7 years ago from Los Angeles

        Andy, I'm glad my hub was helpful. Thanks for voting up!

        Hope you drop by again.

      • profile image

        andycool 

        7 years ago

        Excellent article, voted up! Great ways to deal with slopes, thanks for sharing. - Andy

      • Ms Chievous profile image

        Tina 

        7 years ago from Wv

        Thank You Cat! I will definitely look for these plants! I am thinking of terracing my slope.. someday! Good suggestions!

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