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 Photo: Chicago Botanic GardenName: Stachys spp.(lamb's ears or betonies)
Landscape uses: Lamb’s ears is a great plant for edging beds and softening walks, or massed as a groundcover, or as an accent in the border and rock garden. Betonies bring a casual formality to the border, herb garden, cottage garden or meadow.
Hardiness: USDA Hardiness Zone 5b.
Soft silvery leaves and a low, spreading habit are desirable traits of lamb’s ears (Stachys byzantina) that contribute to its popularity in gardens everywhere.
Perhaps less common, but equally wonderful, are its green-leaved cousins, big betony (S. macrantha) and wood betony (S.officinalis). Betony is a name commonly applied to Stachys species with green leaves and showy flowers, although lamb’s ears are sometimes called woolly betony. These two types of Stachys are so unalike in floral display and foliar character that, at casual glance, it is easy to miss their relationship.
Stachys bears its pink, purple, red, yellow or white blossoms in many-flowered verticillasters on spikes above the foliage.
Cultivated Stachys are informally divided into two groups based on floral display, foliage and plant habit. One group includes S. byzantina and S. thirkei, which have silvery to gray-green, woolly leaves in a sprawling mat of rosettes. Their small flowers are mostly hidden by the fuzzy calyces or the cultivars rarely bloom at all.
In contrast, S. macrantha, S. officinalis and S. monieri produce showy spikes of flowers above bushy mounds of rugose (wrinkled) green leaves. Many Stachys commonly have crenate (scalloped) leaf margins.
In the garden. Stachys are generally easy-to-grow perennials for moist, well-drained soils in full sun to light shade. Good drainage in summer and winter is essential for the health and longevity of S. byzantina and other woolly-leaved species. Their pubescent leaves can trap moisture from high humidity, excessive rain or overhead irrigation, causing foliar rot or meltout.
The evaluation. The Chicago Botanic Garden (USDA Hardiness Zone 5b, AHS Plant Heat-Zone 5) evaluated 22 taxa of Stachys from 1998 through 2004. The comprehensive evaluation of Stachys included the collection of data on ornamental traits, including floral display, leaf color, habit and plant size; cultural adaptability to soil and environmental conditions; disease and pest problems and winter hardiness. Final ratings were based on flower production, plant health, habit quality and winter injury. However, flower production was not factored into the final ratings for the S. byzantina group.
Stachys monieri 'Hummelo' received the highest rating in the trial.
To see the complete ratings in this evaluation, visit www.chicago-botanic.org and search "Stachys."
Richard G. Hawke is plant evaluation manager at Chicago Botanic Garden.
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