Ask Mr. Smarty Plants

We would call sun from noon to sunset "sun" (6 or more hours of sun a day) to "part shade" (2 to 6 hours of sun a day).

We recommend grasses for controlling erosion because of their extensive fibrous root systems that serve to hold the soil in place.  However, seeding grass is not the whole process.  The seeds need moisture to germinate.  If the moisture comes in the form of rain, it is likely to wash the seeds down the bank  before they have a chance to germinate and take root.  There are two possible solutions—an erosion control blanket or pneumatic compost/seed application.  The erosion-control fabric works by slowing the runoff water and allowing sediments to fall out rather than be washed away. Seeds are sown under the erosion-control material and grow up through the matting when they germinate. You can also insert plants into the soil by cutting through the matting. The roots of the plants that are growing through the erosion-control material anchor the soil to stop the erosion. If you use erosion-control blankets made of biodegrable material, they will eventually disappear leaving the plants to control the problem.  Many nurseries carry this erosion control fabric. 

The compost/seed application may be a bit more complicated and expensive than you had in mind since it does require a pneumatic blower, or some mechanical means, to spread the compost/seed mix. The US Composting Council offers information about suppliers of compost and compost technology, but I don't really know if this could be a do-it-yourself project.  You might check with a landscaping or environmental consulting company in your area who might have the machinery to do this to learn about the feasibility and expense of applying the compost/seed mixture this way. You can find the names of Landscape Professionals and Environmental Consultants in your area that specialize in native plants by searching in our National Suppliers Directory.

We will go to our Native Plant Database and find grasses and perhaps some spreading shrubs native to the District of Columbia that should help with your erosion. These are not lawn-type mowable grasses, but more decorative tall grasses that, being native to your area, will be able to cope with soil and climatic conditions. Follow each plant link to the page on the individual plant for information on expected size and sun requirements. 

Small Shrubs for Washington DC:

Comptonia peregrina (sweet fern)

Epigaea repens (trailing arbutus)

Gaultheria procumbens (eastern teaberry)

Symphoricarpos albus (common snowberry)

Grasses for Washington DC:

Andropogon glomeratus (bushy bluestem)

Carex blanda (eastern woodland sedge)

Carex pensylvanica (Pennsylvania sedge)

Carex texensis (Texas sedge)

Chasmanthium latifolium (Inland sea oats)

Elymus canadensis (Canada wildrye)

Muhlenbergia capillaris (hairawn muhly)

Muhlenbergia schreberi (nimblewill)

From our Native Plant Image Gallery:

Comptonia peregrina

Epigaea repens

Gaultheria procumbens

Symphoricarpos albus

Andropogon glomeratus

Carex blanda

Carex pensylvanica

Carex texensis

Chasmanthium latifolium

Elymus canadensis

Muhlenbergia capillaris

Muhlenbergia schreberi