Ground Ivy, or Gill-Over-the-Ground, is the nemesis of every suburban homeowner who prizes purity in his lawn. For more tolerant types, it’s a friendly little plant. It never grows very tall; it has pretty blue flowers; and it makes your whole lawn smell minty when you mow it. This colony was growing in a lawn in Mount Lebanon, where it was blooming in late April.

Gray places this in the genus Nepeta:

NEPETA L. CAT MINT
Calyx tubular, often incurved. Corolla dilated in the throat; the upper lip erect, rather concave, notched or 2-cleft; the lower 3-cleft, the middle lobe largest, either 2-lobed or entire. —Perennial herbs. (The Latin name, thought to be derived from Nepete, an Etruscan city.)

N. hederacea (L.) Trevisan. (GROUND IVY, GILL-OVER-THE-GROUND.) Creeping and trailing; leaves petioled, round-kidney-shaped, crenate, green both sides; corolla thrice the length of the calyx, light blue. (Glecoma L.; Glechoma Benth.) Damp or shady places, near towns—May-July. (Nat. from Eu.)