Ajuga reptans is commonly known as bugle, blue bugle, bugleherb, bugleweed, carpetweed, carpet bugleweed, and common bugle, and traditionally but less commonly as "St. Lawrence plant". It is an herbaceous flowering plant native to Europe. It is invasive in parts of North America. Grown as a garden plant it provides useful groundcover. Numerous cultivars have been selected, of which "Caitlin's Giant" has gained the Royal Horticultural Society's Award of Garden Merit. Ajuga reptans is also a component of purple moor grass and rush pastures, a Biodiversity Action Plan habitat in the United Kingdom.
Ajuga reptans has dark green leaves with purple highlights. It is a spreading and dense ground cover. The leaves grow 5–8 cm (2.0–3.1 in) tall, but in the spring it sends up 10–15 cm (3.9–5.9 in) tall flower stalks bearing many purple flowers. The flowers are frequently visited by flies, such as Rhingia campestris.