Ajuga reptans - Bugle
“This low creeping perennial, a member of the mint family, thrives on woodland edges and in damp grassland. It propagates mainly by throwing rooting runners.”

“A very aggressive, mat forming perennial which spreads by runners. Foliage is bronze-purple, usually variegated and will remain evergreen through the winter if mulched. Able to fill large areas quickly, Bugleweed grows so dense that weeds have almost no chance of germinating. Ajuga spreads so fast that without well planned borders or constant vigilance, Bugleweed can become the invading weed especially in lawns.”