Are there some plant-based erosion control ground cover options for Pacific Northwest US?

Question

Our driveway cuts through the side of a hill. The 'uphill' side in parts is at a perhaps 65 degree angle so steep, and there's a bit of erosion... enough to expose some tree roots.

Ideally we'd use some physical retaining wall solution (stone walls or gabion/reno mattresses) but given that we're broke at the moment, I thought I could at least maybe plant something to hold the soil together until we can afford bigger/better options.

The catch is that it's entirely shaded.

We're in the Pacific Northwest coastal climates.

Is there any sort of spreading non-invasive ground control that we could get to take hole on the hill? Or should we just figure that mechanical retaining walls are the solution?

Answer 1

The problem is that the plants that will spread fast in shade are ones that you may not wish to have indefinitely. Also if the slope only exposes subsoil then you would need to provide better soil to get a decent growth so you are back at terracing to retain topsoil.

These ones work to retain soil and grow in shade but are not cheap to buy in quantity and require good soil and adequate water to do their job. More details here and here

• Pachysandra terminalis Japanese Spurge - commercially available
  • Evergreen, thrives in dry, shady areas, produces attractive white berries in fall.
  • Insignificant fragrant white flower spikes in summer
  • Partial shade to full shade, Acidic, organically rich, moist soil
  • Hardy to -25°C (-11°F) Zone 5 USDA
  • Height: 20cm (8 in), Spread: Indefinite but slow
• Linnaea borealis (Twinflower) is an evergreen low ground cover
• Mahonia nervosa (Cascade barberry) or Oregon grape is evergreen, picky leaves
• Achlys triphylla (Vanilla leaf) creeping rhizomes help retain soil but needs moisture
• Asarum canadense (Canadian wild ginger) we grow it and it is a nicely behaved ground cover, no flowers to speak of but requires good soil and adequate moisture to get established
• Cornus unalaschkensis or Cornus Canadensis(Bunchberry) although not evergreen, it is perennial with rhizomes that will aid in erosion control. Charming plant but not a fast grower
• Polystichum munitum (Western swordfern) is evergreen and grows to 3 feet. Probably your best bet for fast growth