Green Guide: Stachys spp.

Soft silvery leaves and a low, spreading habit are desirable traits of lamb’s ears (Stachys byzantina) that contribute to its popularity in gardens.

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 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.

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. Its silvery leaves are perfect foils for plants with hot- or cool-colored blossoms. Conversely, betonies bring a casual formality to the border, herb garden, cottage garden or meadow. Their glowing purple spikes stand like sentinels in the midsummer garden.

The evaluation
The Chicago Botanic Garden evaluated 22 taxa of Stachys from 1998 through 2004. The comprehensive evaluation included the collection of data on floral display, leaf color, habit and plant size; cultural adaptability; 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 because of the sporadic to nonflowering aspect of some cultivars.

Stachys monieri ‘Hummelo’ received the highest rating in the trial based on strong flower production, plant health, habit quality and winter hardiness. Stachys thirkei is not as adaptable to average garden conditions as S. byzantina.

The impressive floral displays and strong habits of the green-leaved betonies compare favorably to other popular garden perennials. The fuzzy flowers of lamb’s ears add textural interest, but deadheading is recommended to maintain plant health and regenerate leaves. Selecting a nonflowering cultivar such as ‘Big Ears’ or ‘Silver Carpet’ will reduce maintenance too. Deadheading betonies eliminates self-seeding, which may ultimately crowd out the original plants.

To see the complete evaluation, visit: www.chicago-botanic.org/downloads/planteval_notes/no27_stachys.pdf  

– Richard G. Hawke,
plant evaluation manager,
Chicago Botanic Garden