I’m looking to plant in a narrow strip on our retaining walls some “spiller” plants which will overhang the walls (which face north).
I’d prefer evergreen plants which would fill in fairly quickly,
but I could also mix in slower-growing and deciduous plants. There’s great drainage since I have gravel reservoirs
behind each wall, and the part of the plant above the wall will get part to
full sun, though I could overplant them if necessary for a plant that couldn’t
handle full sun.
I would like plants with interesting foliage and form to soften the look of the walls, and so would prefer a furry look to a spiny one. Flowers and fragrance are less
important though always nice, and I’m hoping to have at least 2 or 3 different
plant types with different colored foliage (shades of green are fine).
Some of the plants that occur to me, based on the description of your site, are
Brunnera macrophylla, Epimedium, Geranium phaeum, Stachys byzantina, Lamium
maculatum, and Liriope. Of these, the Geranium and Lamium will trail somewhat, while the others are essentially upright.
Graham Rice’s article on the Royal Horticultural Society site features a selection of recommended trailing (or spilling) plants. Here is another good list of trailing plants for walls.
You could also try entering your site requirements into the plant-finding and
plant selection web pages below:
Great Plant Picks (a local site)
King County’s native plant guide
Missouri Botanic Garden Plant Finder
Royal Horticultural Society Plant Finder
The Miller Library has many books on gardening in the shade, so you may wish to
come in and do some research to help you in your plant selection. Here is a booklist that may be of interest.