Native Plants for Steep Slopes and Erosion Control
By gripping the soil with their more extensive roots, certain native plants can do a better job at erosion control than turf grass, especially in shade areas where grass grows poorly. And no mowing is required!
Other solutions such as speed bumps and check dams may be needed as well, depending on the volume and speed of the water flow. Information about those can be found by clicking here.
Although related, erosion control is not the same as stormwater management, which may require engineering solutions and not just plants. The two goals of stormwater management are to reduce erosion and to reduce the volume of water that hits the streams. Plants can help both by breaking up the flow and infiltrating water into the soil. But if the velocity is too high, smaller plants will just wash away, and the roots of shrubs and trees will become exposed.
Why control erosion?
Sediment will end up somewhere else - against your house, or in the woods smothering plants there, in your neighbor's yard, or ultimately in the Chesapaeke Bay where it smothers the sea grasses that are the basis of that ecosystem.
It takes hundreds of years to build just one inch of topsoil! Human activity has been squandering this precious resource, which of course is essential for plant life, including the food we eat. Earth has lost half of its topsoil in the past 150 years.
Bare soil will erode because of the wind and rain splash. You can armor the soil with dead leaves or at a minimum by covering it with straw while you finish a project or wait for plants to grow.
Need some help?
You could of course hire a native plant landscaping company or one of the many companies with experience in stormwater management. But if you want to work on erosion and stormwater problems yourself, you can consult your local Soil and Water Conservation District. They are there to help landowners with precisely these problems. They may even be able to advise you by email if you send them some photos.
Prince William - Prince William Soil and Water Conservation District
Arlington - StormwaterWise Landscapes
(Independent cities not covered by a Soil and Water Conservation District: Alexandria, Arlington County, Fairfax City, Falls Church, Manassas, Manassas Park)
How to plant on steep slopes:
Remove unwanted plants but only in the area that you are ready to plant.
Choose drought-tolerant native plants with extensive root systems. See below for some suggestions.
If sowing seeds – an inexpensive way to cover a lot of ground – protect them with straw or biodegradable erosion control blanket.
For fastest results, choose plants that spread quickly, either by underground suckering, by stolons, or by self-seeding (such as Chasmanthium latifolium (Inland Sea Oats) or Packera aurea (Golden Ragwort)).
Apply mulch after planting
Plants with any of these features help control erosion (a nice discussion can be found on the Izel website.)
Extensive or deep roots that hold soil and promote infilltration
Strong upright stems that trap soil and slow down the flow of water
Layers of leaves that catch rain before it hits the ground
Strong winter presence
An excellent list of native plants for this purpose can be found on the website of the Northern Virginia Soil and Water Conservation District (NVSWCD). Some additional suggestions not listed there can be found below.
Sensitive Fern (Onoclea sensibilis)
Shrubs may give a more formal look and have the advantage that each plant covers a lot of ground.
Ceanothus americanus (New Jersey Tea). Sun/Part Shade.
Comptonia peregrina (Sweet fern). Sun/Part Shade.
Hydrangea arborescens (Wild Hydrangea). Part Shade/Shade (pictured on the side of a cliff))
Hypericum prolificum (Shrubby St. John’s Wort) Sun/Part Shade
Rhus aromatica (Fragrant Sumac). Sun/Part Shade. Use ‘Grow-Lo’ if a short variety is desired.
Smooth Hydrangea (Hydrabgea arborescens) on a cliff
Creeping Phlox (Phlox subulata)
Perennials (herbaceous forbs)
These are examples of plants that quickly spread sideways and grip the soil tightly. They may spread more than you really like, so be careful!
Chrysogonum virginianum (Green-and-Gold). Sun/Part Shade/Shade.
Iris cristata (Dwarf Crested Iris). Part Shade/Shade.
Monarda fistulosa (Wild Bergamot). Sun/Part Shade. For something a little taller.
Phlox subulata (Moss Phlox). Sun. (pictured)
Pycnanthemum tenuifolium (Narrow-leaved Mountain Mint). Sun/Part Shade.
Grasses or grass-like plants
Carex appalachica (Appalachian Sedge) (pictured)
Panicum virgatum (Switch Grass).
Sorghastrum nutans (Indian Grass)
Appalachian Sedge (Carex appalachia)