thyme (Thymus serpyllum)
This is a lovely alternative to grass. It's a low-growing perennial
that comes in many varieties and thrives in dry, rocky soil.
Aside from a little supplemental water to get it started, this
plant will not need further watering, mowing or fertilizing.
It spreads into a thick carpet of tiny delicate leaves that
hug the ground and give off a wonderful savory aroma when stepped
on. Creeping thyme (Thymus serpyllum) produces tiny, delicate
flowers, and, depending on your location, at certain times in
the summer it will transform into a field of pink or purple.
You shouldn't have to worry about foot traffic causing any harm
to the plant. However, it doesn't do as well in shady areas
and can become a bit patchy.
For a shady alternative, periwinkle (Vinca minor) can produce
a lush green lawn if you have the patience to let it fill in.
It may take a couple of years to become thick and full, but
it doesn't require fertilization or mowing. It also produces
pretty flowers. This plant will grow in the sun, but it doesn't
provide as much cover there and tends toward a more yellowish
hue. Periwinkle is not as nice to walk on as white clover or
bugleflower, but it might be just what you're looking for to
fill in that empty spot under your maple or spruce tree.