Ajuga pyramidalis aka Pyramid Bugle

Ajuga pyramidalis, or pyramidal bugle, belongs to the mint family, Lamiaceae. This low perennial comes from Europe, including Britain and Ireland. It forms clumps and keeps some leaves through winter. Short rhizomes help it spread into a dense ground cover. NC State gives heights of 0.17–0.67 feet [0.05–0.20 metres]. Its listed spread is 0.5–1 foot [0.15–0.30 metres]. RHS gives a broader garden size range. Its upper limits reach 1.6 feet [0.5 metres] tall and 3.3 feet [1 metre] wide.

Dark green leaves form a rosette at ground level. They are simple, oval to egg-shaped, with smooth edges. Dense hairs give the leaves a soft feel. Leaves also grow in opposite pairs along the stems. NC State describes leaves about 0.33 feet [0.10 metres] long. The green stems stand straight and have square cross-sections. Hairs cover the stems, which lack a scent.

Small blue to blue-violet flowers open in spring and early summer. NC State places the main bloom in May and June. Each tubular flower has a lipped, uneven shape. Tight whorls form spikes with a tapering, pyramidal outline. Dark purple bracts sit among the flowers. RHS describes spikes about 0.33 feet [0.10 metres] tall. Bees visit the flowers for nectar. The green fruit splits into four nutlets, each holding one seed.

Grow this plant in moist soil with some shade. NC State also lists full sun as suitable. RHS accepts clay, loam, sand, and chalk across the pH range. NC State favours fertile soil with good drainage. RHS rates it H7; NC State lists USDA zones 5–9. RHS gives two to five years to reach full size. Divide clumps to make new plants. Routine pruning is not needed, according to RHS.

Use it along bed edges, in containers, or beneath shrubs. It also suits rock gardens and wildlife borders. Deer and rabbits tend to leave it alone. NC State also reports tolerance of nearby black walnut trees. Watch its spread into lawns and nearby beds. Rooting runners can make older patches hard to remove. Very wet soil can lead to crown rot. Long spells of extreme dryness can cause dieback. RHS reports few pest problems, though powdery mildew may occur.