Sweet woodruff (an invasive weed) Pachysandra (boring and a snail magnet)
Leadwort (Ceratostigma plumbaginoides) A very hungry competitor.
Some even suggested a small leafed ivy or Vinca Minor. I disagree most strongly on a multitude of issues..
Dwarf beach strawberry. Frageria chiloense (might attract root weevils) Spreads. (MORE NATIVES)
Cornus canadensis, along with the native Trillium, Trillium ovatum and pink fawn lily, Erythronium revolutum. A nice spring show before the maple leafs out. After the fawn lilies and trillium are done, do.annuals
??? or nothing. Erythronium montanum ( white avalanche lily) or E. grandiflorum (Yellow) http://www.dancoephoto.com/Nature/Pacific-Northwest/Pacific-NW-Native-Plants/
Spring bulbs such as Anenome blanda with specie tulip Praestens fuselier or early specie daffodils, followed by ??? (Nothing!)
Isotoma Blue Star Creeper
Blue Spruce Sedum as well as many other ground cover Sedum.
Liriope or Black Mondo Grass with crocus.
Minimalist – *Bark mulch*
My preferences are in bold and I have stuck to the spring bulbs that will die back to the mulch – which come fall will make the necessary rake cleanup a breeze. Japanese Maples need some dormant spraying and leaf cleanup is important for the health of the plant. Having sedums or liriops, mondo grass prevent this. Much less the aggressive vinca or ivy which can actually grow up the trunk.