Lamb's ears are widely used in flower borders. They spread readily, making them effective ground covers for sunny areas if you do not mind them taking over. If you wish to start a new patch of them somewhere else, either dig up the new plants created through self-seeding or divide in spring. As drought-tolerant perennials, they are candidates for rock gardens. Their silvery color is fun to play with when experimenting with color theory in your landscape design. The flower spikes reach 12 to 18 inches in height, but the rest of the plant stays much closer to the ground and has a spread of about 1 foot. When it blooms, the flower color is most typically light purple.
Indigenous to parts of the Middle East, lamb's ears are considered invasive plants in parts of North America. They spread both by self-seeding and through creeping stems that root wherever they make contact with the soil. If you wish to control them, deadheading will address the former, but not the latter, which you will have to control with some type of edging. The plants are also deer-resistant and rabbit-proof.
Light
Grow lamb's ears in full sun in northerly climes. In desert areas, though, it can profit from partial shade.
Soil
This perennial flower thrives in poor soil that is well-drained and has a slightly acidic soil pH. Treat it as you would any plant (many herbs fall into this category) associated with a Mediterranean climate.
Water
Lamb's ears are drought-tolerant in the North; you will lose some of the older leaves during dry spells (they brown up and look quite unsightly, so remove them), but the plant itself will survive. Avoid watering the plants overhead, as the leaves will rot if they get too wet.
Temperature and Humidity
This plant can withstand a range of temperatures but as a ground cover, it dislikes humid conditions. The humidity makes lamb's ear susceptible to leaf diseases. Because it spreads so readily, you will usually have new plants with which to replace the old, rotted plants.
Fertilizer
Avoid crowding lamb's ear to promote sufficient air circulation. Keeping them off the damp ground is a good idea. Mulch around them to accomplish this. Every spring, a thin layer of compost will help with growth.
Varieties of Lamb's Ear
The Stachys genus has many species, byzantina being just one. A common name often used for the genus is "betony." Stachys byzantina, sometimes called "wooly betony," comes in a few different cultivars:
Big Ears is a popular cultivar partly because it has just that: bigger ears than the standard type. Those who grow lamb's ears only for the foliage will be glad to know that this cultivar sometimes goes years without blooming. It also has better disease-resistance.
Silver Carpet is another cultivar that does not flower often. Staying short at 4 to 6 inches high, with a spread of 9 to 18 inches, its dimensions suit it to use as a ground cover.
Cotton Boll gets its name from the fuzzy formations on its flower stalks where flowers should emerge but often do not, leaving gardeners, instead, with much more interesting-looking cotton bolls.
Silvery, fuzzy leaves are the signature of Stachys byzantina, but other species have green, smooth leaves. They are valued more for their flowers, which occur more regularly than on Stachys byzantina. Counting the height of the flower stalks, these plants reach about 2 feet tall, so they are not as suitable for ground covers as is Stachys byzantina.
Pruning
Some growers find the flower stalks gangly. If that is your opinion of them, then just prune them off. Every three or four years you can divide the plants in the spring or just remove the dead centers if you prefer to maintain the clumps.
Problems and Pests
If your summer weather is particularly humid, the humidity can cause the plants to rot out from the center. The goal is to avoid letting the foliage rot or get diseased. Sowbugs are attracted to diseased foliage, so removing the dead leaves helps prevent the pests.