Heal-all. Prunella vulgaris.
Lamiaceae, the mint family.

Plant: Erect or prostrate square stems, 4"-18",with opposite leaves and terminal spikes of small, purple, mint-like flowers. Perennial.
Flowers: Violet to purple, bilateral, classic "mint" flower shape with two-lipped corolla. Upper lip larger than lower. Flowers in dense, cylindrical, terminal spikes or heads, 1/2"-2". Individual flowers protrude between hair bracts on the head.
Leaves: Opposite, ovate, 1"-3", with short stems.
Blooming: May-September
Habitat: Fields, lawns, roadsides.

Comments: Also called "Self-heal", this member of the mint family is nearly cosmopolitan in the northern hemisphere. Both native and introduced populations are present in the US. The common name refers to the use of the plant in traditional herbal medicine as a remedy for throat and other ailments. The plant seems to have anti-inflammatory and certain antiseptic properties.

Where to find it: Common in the lawn areas of the park.