Ajuga or "Bugleweed" Plants

A Ground Cover That Fills in Quickly (Alas, a Bit Too Quickly)

Ajuga ground cover in bloom with dark foliage.
David Beaulieu

Classification for Ajuga Plants:

Taxonomy classifies bugleweed or "bugle" as Ajuga reptans. However, this is a case where the genus name has come to be so widely used in everyday language as to function virtually as a common name; in such cases, there is no need to capitalize the first letter of the word. The plant is in the mint family (Lamiaceae).

Ajuga plant is an evergreen, perennial ground cover.

Characteristics, Cultivars, Care:

Bugleweed is a fast-growing ground cover that usually creeps within just a few inches of the ground (the species name, reptans, means "creeping"), although when in flower (if you count the flower spike), it may reach a height of 6 inches or more. Ajuga plants bloom from spring to mid-summer.

Flower color is typically blue to purple, but A. reptans Pink Elf is a cultivar that has deep pink blooms. There is more variety from which to choose when it comes to the appearance of the leaves, rather than the flowers. Some examples are:

  • A. reptans Atropurpureum: bronze-purple foliage
  • A. reptans Chocolate Chip: darker leaves than the species plant, including a hint of what some call a "chocolate brown"
  • A. reptans Burgundy Glow: variegated foliage that is tricolored (white, pink, and green)
  • A. reptans Rainbow: Like Burgundy Glow, it is mottled, with hints of magenta, pink, peach, and off-white invading the bronze-green base color.
  • A. reptans Black Scallop has perhaps the darkest leaves of all of the cultivars. 
  • If you want something brighter, go with Toffee Chip. Its bicolored leaves are white and green.

Ajuga spreads aggressively via runners, a fact that should alert you to its potential to be invasive. To control it in your planting beds, you will have to be faithful about pulling it out from where it does not belong if you wish to check its spread. If you are not faithful about controlling it, it will soon gain a toehold and become a pest. Controlling its spread is usually the main care required, especially in Northern landscapes. In the South, you will have to watch out for crown rot, also called "Southern blight." This is a fungus (Sclerotium rolfsii). You can help prevent it by assuring that your soil drains well.

Planting Zones, Origin, Growing Conditions:

Bugleweed can be grown in planting zones 3 to 10. This ground cover is indigenous to Eurasia.

An easy ground cover to grow, bugleweed will grow in sun or part shade, and it is not fussy about soil so long as the drainage is good.

Uses and a Warning:

Spreading through the use of rhizomes, ajuga will form a dense mat to keep down weed growth, which is one reason why it is so popular as a ground cover. In fact, another common name for the plant is "carpet bugle." Ajuga plants can also be used for erosion control. Deer seem not to like the plants, making these spreading dynamos deer-resistant ground covers. They are also rabbit-proof flowers.

Bugleweed is so tough that it can even grow under black walnut trees (Juglans nigra). These are the trees that produce juglone (a chemical that discourages the growth of potential plant competitors), and many plants will not grow under black walnut trees for this reason.

Like yarrow, a traditional use for ajuga plant was a medicinal, herbal use that was of paramount importance on the battlefield: Both herbs were used to treat wounds.

Ajuga is an invasive plant in North America. In fact, it has naturalized in some parts of the continent. If you have gardened for a while, the invasive nature of the plant will not surprise you. Two facts about it should serve as red flags:

  • It is a mint-family member (this plant family is notoriously aggressive).
  • And its species name is reptans. Assume the worst when you see that word in a plant name, as if you were being warned: "It creeps, it crawls, it conquers." A similar species name that indicates the same kind of growth habit is repens, as in Ranunculus repens, the creeping buttercup.

The species names, reptans and repens, do not always signify that the plant in question has an invasive nature (that will depend on the particular plant, on your geographical location, and on the growing conditions), but these names should raise doubt in your mind if your preference is for well-behaved plants.

Other Types of Ajuga Plants

Two other species of bugleweed do exist, in addition to reptans. However, neither are low-growing enough to to serve as substitutes for reptans as flowering ground covers. The Geneva kind (A. genevensis) grows up to 14 inches tall, the upright type (A. pyramidalis) to 10 inches tall. That's too bad, because neither of these species spreads via rhizomes, meaning they have far less chance of becoming invasive. Cultivars and varieties with pink flowers include:

  • A. genevensis var. rosea 
  • A. pyramidalis Pink Beauty

A Final Word on the Use of the Plant as a Ground Cover:

Although an attractive plant, it is often better to use Ajuga reptans only in the following type of area in a landscape:

In other cases, ajuga is too invasive for many gardeners' tastes. Constantly having to pull out its "colonists" makes it a high-maintenance plant in an age when many people are seeking just the opposite: namely, low-maintenance landscaping.