Ask Mr. Smarty Plants

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 your steep bank  before that have a chance to germinate and take root.  One possible solution is to use an erosion control blanket.  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. 

Here are some candidate grasses and sedges native to your area.  Since I don't know all the growing conditions (e.g., available sun and moisture) at your site, you should check the GROWING CONDITIONS section for each species to determine if it is suitable for your site:

Andropogon virginicus (broomsedge bluestem)

Carex blanda (eastern woodland sedge)

Chasmanthium latifolium (Inland sea oats)

Eragrostis intermedia (plains lovegrass)

Muhlenbergia schreberi (nimblewill)

Here are some other plants that you could use on the bank.

Artemisia ludoviciana (white sagebrush)

Conoclinium coelestinum (blue mistflower)

Cephalanthus occidentalis (common buttonbush) would do well at the base of the bluff on the edge of the creek.

Ferns would work in mostly shady areas.  Here are a few suggested ones.

Dryopteris marginalis (marginal woodfern)

Osmunda cinnamomea (cinnamon fern)

Andropogon virginicus

Carex blanda

Chasmanthium latifolium

Eragrostis intermedia

Muhlenbergia schreberi

Artemisia ludoviciana

Conoclinium coelestinum

Cephalanthus occidentalis

Dryopteris marginalis

Osmunda cinnamomea