What is this low growing square-stemmed plant in my lawn?

Question

I have a small, dense, spreading herbaceous perennial plant in my lawn. I don't have anything against it, but I would like to know what it is. It has slightly square stems and rounded leaves. It has small purple flowers sometimes, and looks a lot like a Prunella when in bloom. It tends to grow in poor, rocky soil where the grass gets thin.

Answer 1

This looks like Ajuga reptans or bugleweed. It has many cultivars and changes its habit depending on the environment. It is six inches tall when in flower. For the rest of the year it is just a few inches high.

This plant does not taste good to deer but is considered invasive in parts of North America.

If it starts getting out of hand you can pull it out by its tap root and fertilize or top dress to encourage the grass to out grow it.