Prunella vulgaris grows 5 to 30 cm high (2-12inches), with creeping, self-rooting, tough, square, reddish stems branching at leaf axis.
The leaves are lance shaped, serrated, and reddish at tip, about 2.5 cm (1 inch) long and 1.5 cm (half an inch) broad, and growing in opposite pairs down the square stem. Each leaf has 3-7 veins that shoot off of the middle vein to the margin. The stalks of the leaves are generally short, but can be up to 5 cm (2 inches) long.
The flowers grow from a clublike, somewhat square, whirled cluster; immediately below this club are a pair of stalkless leaves standing out on either side like a collar. Flowers are two lipped and tubular. The top lip is a purple hood, and the bottom lip is often white; it has three lobes with the middle lobe being larger and fringed upwardly. Flowers bloom at different times depending on climate and other conditions, but mostly in summer (from June to August in the USA).
Self-heal propagates both by seed and vegetatively by creeping stems that root at the nodes.