Plant taxonomy classifies lamb's ears as Stachys byzantina. The common name serves as both the singular and the plural form. People sometimes say "lamb's ear plant," but that's less descriptive, since, after all, this perennial favorite does have more than one "ear" (that is, leaf). Stachys byzantina plants are classified as herbaceous perennials.
Although grown more for the texture and color of its foliage than for its bloom, my lamb's ears does produce light purple flowers on tall spikes (they bloom in late June in my zone-5 garden). Some growers find the flower stalks gangly and prune them off. The plant's texture can best be described as "fuzzy" or "velvety." Lending further interest to the foliage is its silvery color. The flower spikes reach 12-18 inches in height, but the rest of the plant stays much closer to the ground and has a spread of about 1 foot.
'Big Ears' is a popular cultivar partly because it has just that: bigger "ears" (that is, leaves) than the standard type. And those who grow lamb's ears only for the foliage will be glad to know that this cultivar sometimes goes years without blooming. It is also said to have better disease-resistance. Another interesting cultivar is 'Hill Dog,' which has flowers of a light red color. Stachys densiflora 'alba' is a white-flowering cultivar.
Some beginners to plant identification confuse this plant with common mullein (Verbascum thapsus), another plant with silver leaves and a tall flower spike. But common mullein's flowers are a different color (usually yellow). This Old World native has naturalized in much of the New World; it is a common roadside weed here in New England.
Planting Zones, Sun and Soil Requirements
Lamb's ear plants can be grown in planting zones 4-7.
Grow lamb's ears in full sun in northerly climes. In desert areas, though, it can profit from partial shade. 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. They 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.
Uses in Landscape Design, How to Control Its Spread
The plants 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 "volunteers" (that is, new plants that self-seeded) 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 plants are also deer-resistant and one of the rabbit-proof flowers.
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.
Care for Lamb's Ears
Avoid watering the plants overhead, as the leaves will rot if they get too wet. For the same reason, avoid crowding to promote sufficient air circulation. Keeping them off the damp ground, likewise, is a good idea: mulch around them to accomplish this. A problem with this ground cover is that it dislikes humid conditions, in which it is susceptible to leaf diseases. Its saving grace in such cases, though, is that, because it spreads so readily, you will usually have new plants with which to replace the old, rotted plants.
Origin of the Name, and a Note on the "Texture"
The common name is descriptive: lamb's ears produces leaves with a shape similar to that of a real lamb's ears; they're also velvety soft, further lending themselves to the comparison. The first half of the scientific name is also descriptive. The genus name, Stachys, is Greek for "an ear of grain," referring to the shape of the flower spikes. The specific epithet, byzantina, refers to the plant's Middle Eastern origin, including an area that was once part of the Byzantine Empire.
Note: When we speak of "texture" in landscape design, we are usually referring to contrasting leaf forms. But the foliage of lamb's ears has an interesting "texture" in the more usual sense of that term. Upon seeing the foliage, one is tempted to reach out and stroke it.