Ajuga or Bugleweed
It is hardy – surviving nicely in USDA 3 to 9.
Light Levels
Ajuga prefers light shade to full shade and tends to be smaller, shorter and less healthy in the full hot sun. And in an area that it likes, it will grow 2 to 5 inches tall (depending on variety) and spread to 12 to 18 inches or to the entire yard (whichever comes first).
Invasive!
Yes, it is a spreader. But it spreads over the ground so you can (and should) contain it with a shovel by edging every spring and mid-summer. As a ground cover, I have found its spread to be slow but steady. This is comparison to other more aggressive ground covers such as goutweed. It will invade lawns and becomes a major pest (derisively referred to as "buglelawn")
Soils
It grows well in average soil but will survive in soils with more clay or sand as major components. It will winter kill (rot) in heavy clay soils.
Care Requirements
Given the above, if you want to see flowers you do have to provide adequate water when the plant is in the shade. This is particularly true when it is in competition with aggressive tree roots. This is not a plant for dry shade. Interestingly enough, there are gardener reports of this plant doing quite well in areas that are damp in spring and early summer but dry up for the fall.
It requires no special care. Put it in the ground, water for a few weeks to get it established and then let it alone.
Some companies advertise it as being able to be walked on. I wouldn’t bet the farm on this; it might take a light walking over once or twice but it will not handle regular foot traffic.
Bloomtime
Ajuga blooms (normally with a deep, dark blue) in very early spring and sporadically thereafter. And you’ll see a range of foliage colours ranging from greens, to bronzes, multi-colours and almost purplish blacks. The only Ajuga I’ve found to be a bit tricky is the multi-coloured foliage plants; they are not reliably hardy into USDA zone 4.
The only problem you'll sometimes see with Ajuga is a little botrytis or grey mould. This will cause some leaves to shrivel up or flowers to abort. A fungicide spray with lime sulphur should stop this.
Propagation
In spring, divide this plant and replant immediately.
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