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Gardening Answers Knowledgebase

Plant Answer Line Question

Keywords: Berberis, Vaccinium ovatum, Polystichum munitum, Amelanchier, Acer circinatum, Slope stabilization and soil erosion, Corylus, Alnus, Philadelphus lewisii

Can I plant groundcovers, shrubs, and trees to stabilize a steep slope?


There are several resources which will help you in selecting plants to prevent erosion and mudslides on your slope.

Please note that these articles are merely suggestions and should not be construed as advice. We are librarians, not engineers!

None of our standard books on trees mentions the soil binding quality of tree roots. However, the Miller Library does have very good technical books and articles on slope stabilization. (For example, Slope Stabilization and Erosion Control: A Bioengineering Approach, edited by R.P.C. Morgan and R.J. Rickson, 1995.)

I do want to note one thing that many articles mention: no amount of established vegetation will hold a steep slope if other forces are present that would contribute to a landslide.

The Department of Ecology website has a list of appropriate plants.

Additionally, there are a number of books with information on the subject. Vegetative Contribution to Slope Stability at Magnolia Park (by Kathy Parker, 1996) recommends Oregon grape (Mahonia), which she suggests for gentle slopes.

Other smaller plants she lists are:
Polystichum munitum (native sword fern)
Vaccinium ovatum (evergreen huckleberry)
Symphoricarpos albus (snowberry)

Larger shrubs in her list:
Alnus rubra (red alder)
Philadelphus lewisii (mock orange)
Sambucus racemosa (red elderberry)

Small trees:
Acer circinatum (vine maple)
Amelanchier alnifolia (serviceberry)
Corylus cornuta (hazelnut)

For steeper slopes, Parker says that they may not be good candidates for vegetative rehabilitation unless you put in some kind of structure. She says that Jute mats can be used in conjunction with native seed, mulch, and shrubs, if carefully anchored. She also mentions a Weyerhaeuser product called Soil Guard.

Steep Slope Stabilization Using Woody Vegetation (by Leslie Hennelly, 1994) has a plant list, as well as a chart which indicates plants used to control erosion, the degree of the slopes, and the rate of success in resisting erosion.

Two titles which focus more on the garden design aspect of planting on a slope are Hillside Gardening : Evaluating the Site, Designing Views, Planting Slopes (by William Lake Douglas, 1987) and Hillside Landscaping (by Susan Lang and the editors of Sunset Books, 2002).

Date 2017-04-19
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Plant Answer Line Question

Keywords: Hydrangeaceae (Hydrangea family), Native plants--Washington, Philadelphus lewisii

What is the specific habitat of the Philadelphus lewisii (wild mock orange)?
What does this plant need from the habitat in order to survive?
What range does the Philadelphus lewisii grow in?
What family is it in?
What other plants does it often grow around?
What specific habitat does it need?
Where does it grow?
Is it an annual or a perennial plant?


Philadelphus lewisii is a Northwest native, a common shrub east and west of the Cascades. According to Trees and Shrubs for Pacific Northwest Gardens, 2nd edition by John A. Grant and Carol L. Grant, it will "thrive in almost any garden soil in either full sun or partial shade, and are of the easiest possible culture. The hybrids respond noticeably to generous cultivation , fertilizer, and water. (It belongs to) the group of summer-flowering shrubs that are best pruned immediately after flowering."

Philadelphus lewisii is a deciduous shrub (in other words, it is not an annual and, although it has a long life span, it is not like an herbaceous perennial that completes its life cycle and starts over the next spring--it is a woody deciduous plant which loses its leaves in winter). (Source: The Royal Horticultural Society A-Z Encyclopedia of Garden Plants, edited by Christopher Brickell; Dorling Kindersley, 1996).

Here is a link to a page from the Washington Native Plant Society about Philadelphus lewisii and its habitat.

It is a Northwest native (state flower of Idaho), and grows throughout Western North America (from British Columbia south to Oregon), southern Europe, and eastern Asia.

The genus Philadelphus grows in rocky woods, semi-desert, and open areas in wet forest. In gardens, it prefers loamy soil and moderate sun.

The genus Philadelphus belongs to the Hydrangeaceae family.

Date 2017-06-09
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Garden Tip

Keywords: Zinnia, Cornus stolonifera, Philadelphus lewisii, Salix, Butterflies

Want to encourage butterflies to take up residence in your garden this year? Red Osier Dogwood and willows are just a few of the plants that caterpillars eat, while adult butterflies drink the nectar from Western Mock Orange and zinnias. Read a brochure produced by the Washington chapter of the North American Butterfly Association to learn more about what plants support butterflies (pdf).For a print copy send $5 to Butterfly Gardens & Habitats, 909 Birch St., Baraboo, WI 53913 USA. Specify "Western Washington")

Date: 2007-05-16
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May 23 2018 14:32:42