Ajugas, also known as bugleweeds, native to Europe, Asia, and Africa, are low growing, creeing or clump forming members of the mint family, Lamiaceae. Although there are about forty species of ajugas, only three are commonly grown in the US where they are used primarily as ground covers because of their attractive leaves. Evergreen in mild climates, the leaves show considerable variation in color and texture depending on the variety. The small two-lipped flowers are produced in lat spring to early summer on three to five inch long spikes and may be white, pink, and violet blue. Ajugas do best in average to rich, well-drained soil and partial shade but tolerate full sun. Plants may be propagated by cuttings in spring or summer, or division anytime during the growing season. Aphids and can be problems and crown rot can wipe out an entire planting. Crown rot can be reduced by division every two to three years, planting in well ventilated areas with good drainage, application of fungicide, and removal of fallen leaves in autumn.
These three species of ajugas are perennials that do well as groundcovers as they form dense mats that choke out most weeds. They are especially useful in dry shade under trees where other plants have difficulty growing. Ajugas are also good edgers, but use with A. reptans with caution as it can be invasive into lawns. Plants can be pruned by clipping or mowing.
Geneva Bugleweed (A, genevensis)
This upright, clump-forming plant spreads slowly and tolerates more sun than the A. pyramidalis or A. reptans if moisture is sufficient. The basal leaves are dark green and 4-5” long. Blue or pink flowers are carried on two inch tall loose spikes.
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Height: 6-12”
Hardiness: Zones 4-9
Outstanding Selections:
‘Brockbankii’ (shorter and more vigorous than species with darker blue flowers)
‘Pink Beauty’ (pink flowers on 6-8” stems)
Ajuga pyramidalis
The slowest growing of these three ajugas, A. pyramidalis is upright and has dark green leaves three to four inches long . The dense flower spikes are four to six inches long and have large purple bracts pressing up against the bright blue flowers. May form stolons in fall.
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Height: 6-9”
Hardiness: Zones 3-9
Outstanding Selection: ‘Metallica-Crispa (reddish-brown leaves with metallic appearance and crinkly texture.)
Common Bugleweed (A. reptans)
Vigorous and fast growing, this stoloniferous prostrate species can quickly overtake a lawn so use it away from areas where it will not be appreciated. The leaves are two to three inches long and dark green or bronze. Flowers are blue and produced on dense spikes. Breeding programs have produced many excellent cultivars that vary in both flower and leaf color, and are less spreading than the species. A. reptans can tolerate dry conditions better than the other ajugas.
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Height: 4-10
Hardiness: Zone 3-9
Outstanding Selections:
‘Alba’ (White flowers; 8” tall)
‘Bronze Beauty’ (Purple flowers, bronze-purple leaves; 6” tall)
‘Burgundy Glow’ (Foliage a blend of pink, white, rose and green, turning bronze in fall; blue flowers; 4” tall; intolerant of dry conditions)
‘Catlin’s Giant’ (Bronze green foliage; blue flowers; 8” tall spikes)
‘Rosea’ (Pink flowers; 8” tall)
‘Variegata’ (Gray green leaves edged and splashed with cream; blue flowers; 4” tall; tolerates deep shade)
Photo of Ajuga pyramidalis by Jean-Pol GRANDMONT