ISSUE 27, 2005 Evaluation Notes A Comparative Study of Cultivated Richard G. Hawke, Plant Evaluation Manager

oft silvery and a low, spreading including Nepeta, and Salvia. health and longevity of S. byzantina and habit are desirable traits of lamb’s ears Stachys bears its pink, purple, red, yellow or other woolly-leaved . Their S() that contribute to white blossoms in many-flowered pubescent leaves can trap moisture from its popularity in gardens everywhere. verticillasters on spikes above the foliage. high humidity, excessive rain or overhead Perhaps less common, but equally Cultivated Stachys are informally divided irrigation causing foliar rot or meltout. The wonderful, are its green-leaved cousins, big into two groups based on floral display, health of lamb’s ears tends to decline during betony (S. macrantha) and wood betony (S. foliage and plant habit. One group includes flowering, but deadheading regenerates officinalis). Betony is a name commonly S. byzantina and S. thirkei, which have leaves and improves plant vigor. applied to Stachys species with green leaves silvery to gray-green, woolly leaves in a Lamb’s ears is a great plant for edging and showy , although lamb’s ears are sprawling mat of rosettes. Their small beds and softening walks, or massed as a sometimes called woolly betony. These two flowers are mostly hidden by the fuzzy ground cover, or as an accent in the border types of Stachys are so unalike in floral calyces or the rarely bloom at all. display and foliar character that, at casual In contrast, S. macrantha, S. officinalis and glance, it is easy to miss their relationship. S. monieri produce showy spikes of flowers SOFT SILVERY LEAVES AND A Stachys is in the mint above bushy mounds of rugose (wrinkled) LOW SPREADING HABIT ARE () and features the distinctive green leaves. Many Stachys commonly have , familial traits of bilabiate (two-lipped) crenate (scalloped) margins. DESIRABLE TRAITS OF LAMB’S flowers, opposite leaves and square stems. Stachys are generally easy-to-grow The arrangement of its flowers in perennials for moist, well-drained soils in EARS (STACHYS BYZANTINA) verticillasters (false whorls) is a trait that full sun to light shade. Good drainage in Stachys shares with a number of its kin summer and winter is essential for the THAT CONTRIBUTE TO ITS POPULARITY IN GARDENS EVERYWHERE.

Richard Hawke Richard and rock garden. Its silvery leaves are perfect foils for 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 Study The Chicago Botanic Garden (USDA Hardiness Zone 5b, AHS Plant Heat-Zone 5) evaluated 22 taxa of Stachys from 1998 through 2004. The goal of the comparative trial was to identify outstanding Stachys through an assessment of their ornamental traits, disease and pest resistance, cultural adaptability and winter hardiness. All plants were grown in side-by-side plots for easy comparison. The evaluation site received approximately 10 hours of full sun during the growing season and was openly exposed to wind in all directions. The well-drained, clay-loam soil was amended with composted leaves and had a pH of 7.4 throughout the evaluation term. Maintenance practices were kept to a minimum to simulate home garden culture. Stachys macrantha ‘Superba’ 2 Plant Evaluation Notes CHICAGO BOTANIC GARDEN

Water was provided as needed and no turf. Plant traits and evaluation specifics for only. Despite the fact that ‘Wave Hill’ fertilizer was applied. The spent flowers of the 20 taxa that completed the trial are produced some flowering stems in each year Stachys byzantina were regularly removed; shown in Table 1. of the trial, it was essentially the same plant whereas, other taxa were deadheaded in Stachys byzantina and cultivars featured as ‘Big Ears’ in all other traits. The heavy alternate years to observe their repeat thick woolly leaves with some variation in production exhibited by S. byzantina flowering capacity. Mulch consisting of color, size and degree of pubescence noted. caused a severe decline in plant health shredded leaves and wood chips was placed The pale silvery green leaves of ‘Big Ears’ resulting in stem dieback. Beginning in the around the plants for water conservation and ‘Wave Hill’ were less pubescent and third year of the trial, floral stems were and weed suppression. No winter protection typically one inch longer and wider than routinely removed before flowering ended was provided. the species. ‘Cotton Boll’, ‘Primrose Heron’ in an effort to maintain plant health. and the species had similar-sized leaves; Stachys thirkei looks like a miniature Observations however, ‘Primrose Heron’ had lime-yellow lamb’s ears, with small, felted gray-green The comprehensive evaluation of Stachys leaves that eventually faded to gray-green. leaves. Unfortunately, it did not perform as included the collection of data on The leaves of ‘Silver Carpet’ were shorter well as S. byzantina. The plants thrived in ornamental traits, including floral display, and narrower than the species but the same the early trial years despite significant leaf color, habit and plant size; cultural silvery color. The cultivars generally had crown injury during the first winter of adaptability to soil and environmental dense mat-forming habits, but ‘Primrose 1998-1999. Plants quickly recovered in conditions; disease and pest problems; and Heron’ was more clumping than spreading. 1999 but suffered additional damage in the winter hardiness. Final ratings are based on Repeated winter injury and slow winter of 1999-2000. Wet weather in the flower production, plant health, habit regeneration of stems each spring summer of 2000 further weakened the quality and winter injury; however, flower contributed to the less vigorous habit of remaining plants, which eventually died production was not factored into the final ‘Primrose Heron’. during the winter of 2000-2001. ratings for the S. byzantina group because Flower production and floral display The small, green leaves of Stachys of the sporadic to nonflowering aspect of varied widely among the Stachys byzantina discolor were somewhat intermediate some cultivars. Two taxa were eliminated cultivars. In general, the flowers were small between lamb’s ears and betony, being before the trial ended. Stachys byzantina and partially hidden by the fuzzy calyces; rugose above and woolly gray beneath. It ‘Helen von Stein’ is a of ‘Big Ears’; however, ‘Cotton Boll’ is a sterile form, had the largest flowers and was the only thus, redundant in the study. Stachys with the flower clusters modified into fuzzy betony in the trial with yellow flowers. palustris was planted in May 2000 but was balls along the spike. ‘Big Ears’ and ‘Silver Stachys discolor had a similar habit to lamb’s removed the following year when shoots Carpet’ are often listed as nonflowering, but ears but was not a vigorously spreading were observed sprouting all over the test both produced a few floral stems in one year plant. Plants were healthy and floriferous plot and spreading into the surrounding

Table 1: Plant Characteristics and Performance Summary Ratings Overall Stachys Flower Color Flower Bloom Period Flower Foliage Color Plant Plant Rating Length Coverage1 Height2 Width

1 ★★★★ byzantina purple ⁄2 in. mid Jun-mid Aug 60-80% silvery green 9 in./30 in. 26 in. ★★★★ byzantina ‘Big Ears’ does not flower▲ silvery green 14 in. 30 in. ★★★★ byzantina ‘Cotton Boll’ silvery, fuzzy n/a early Jul-mid Aug 80-100% silvery green 10 in./18 in. 30 in. 1 ★★★★ byzantina ‘Primrose Heron’ purple ⁄4 in. early Jul-mid Aug <20% lime-yellow 9 in./16 in. 20 in. ★★★★ byzantina ‘Silver Carpet’ does not flower▲ silvery green 8 in. 30 in. 1 ★★★★ byzantina ‘Wave Hill’ purple ⁄2 in. early Jul-late Aug <20% silvery green 12 in./32 in. 30 in. 1 ★★★★ discolor pale yellow 1 ⁄2 in. early Jun-late Jul 60-80% green 6 in./10 in. 18 in. ★★★ macrantha purple-pink 1 in. early Jun-early Aug• 20-40% green 12 in./18 in. 24 in. ★★★★ macrantha ‘Robusta’ purple 1 in. early Jun-early Aug• 80-100% green 18 in./24 in. 26 in. ★★★★ macrantha ‘Superba’ purple 1 in. mid Jun-early Aug• 80-100% green 24 in./27 in. 28 in. 1 • ★★★★ maxima purple ⁄2 in. late Jun-late Aug 80-100% green 9 in./18 in. 18 in. 1 • ★★★★ minor purple ⁄2 in. late Jun-late Aug 80-100% green 9 in./16 in. 20 in. 1 • ★★★ monieri pink ⁄2 in. early Jul-mid Aug 40-60% green 6 in./12 in. 20 in. 1 • ★★★★★ monieri ‘Hummelo’ violet ⁄2 in. mid Jun-early Aug 80-100% green 12 in./24 in. 20 in. 1 ★★★ monieri ‘Saharan Pink’ pink two-tone ⁄2 in. early Jul-late Aug 40-60% green 8 in./14 in. 18 in. 1 • ★★★★ officinalis purple ⁄2 in. mid Jun-mid Aug 80-100% green 12 in./30 in. 30 in. 1 • ★★★★ officinalis ‘A l b a’ w h i t e ⁄2 in. mid Jun-early Aug 80-100% green 12 in./24 in. 26 in. 1 • ★★★ officinalis ‘Dwarf White’ white ⁄2 in. late Jun-late Aug 40-60% green 3 in./7 in. 14 in. 1 • ★★★★ officinalis ‘Rosea’ pink ⁄2 in. mid Jun-early Aug 60-80% green 12 in./28 in. 27 in. 3 ★★ thirkei magenta ⁄8 in. early Jun-mid Jul 20-40% gray-green 3 in./14 in. 24 in.

Overall Ratings: ★★★★★ excellent, ★★★★ good, ★★★ fair, ★★ poor. 1Flower coverage ratings: excellent 80-100%; good 60-80%; fair 40-60%; poor <20%. 2First measurement is height to top of foliar mound; second measurement is full height including flowering stems. ▲Plants produced flowering stems in one out of seven evaluation years. •Repeat flowering was observed in each year of the trial regardless of whether or not plants were deadheaded. CHICAGO BOTANIC GARDEN Plant Evaluation Notes 3 Richard Hawke Richard Photographed at Heronswood Nursery by Richard Hawke Richard Nursery by at Heronswood Photographed Photographed at Olbrich Botanical Gardens by Richard Hawke Richard by at Olbrich Gardens Botanical Photographed

Stachys byzantina ‘Big Ears’ Stachys byzantina ‘Cotton Boll’ Stachys monieri ‘Hummelo’ each year of the trial but did not thrive in flowers. ‘Dwarf White’ received good moderate to severe decline in plant health. the test garden. ratings in the first few years of the trial, but Deadheading improved health and Overall, the green-leaved betonies got diminishing plant vigor over the course of encouraged foliar regeneration. The green- high marks for floral display, plant health the trial eventually resulted in a lower leaved taxa were deadheaded every other and robust habits, with Stachys monieri rating. Stachys minor and S. maxima were year to determine their repeat flowering ‘Hummelo’ receiving the top rating. Unlike the same plant in the trial and are likely capacity; that is, whether removing spent S. byzantina, flower production was an only compact selections of S. officinalis. flowers played a role in generating a second important trait in determining final ratings Stachys minor is listed as a variety of S. bloom. The degree of repeat flowering was for this group. Stachys macrantha ‘Robusta’ monieri in the RHS Plant Finder but no shown to be unaffected by whether or not and ‘Superba’ had darker purple flowers and reference was found for S. maxima. Despite plants were deadheaded. Repeat-flowering were more robust than the species. These their uncertain identity, both species were taxa are noted in Table 1. cultivars were similar in appearance but exceptionally floriferous plants with A proliferation of seedlings was ‘Superba’ was 6 inches taller and bloomed a compact habits. observed in the test plots of the following week later than ‘Robusta’. Their dark green There was no consistent pattern of taxa in one or more years: S. officinalis, S. leaves remained healthy and ornamental winter injury noted in the trial, except for officinalis ‘Alba’, S. officinalis ‘Dwarf White’, throughout the summer. Stachys macrantha Stachys byzantina ‘Primrose Heron’, which S. officinalis ‘Rosea’, S. maxima, S. minor, S. received a fair rating because of low flower suffered crown damage each winter between monieri and S. monieri ‘Saharan Pink’. production and a weak habit. Stachys 1999 and 2004. The other lamb’s ears with Excessive seedling production affected the macrantha is similar to S. officinalis and S. crown damage in more than one year were plots of S. monieri, S. monieri ‘Saharan Pink’ monieri in general appearance but is bolder- ‘Big Ears’ (1999, 2003), ‘Cotton Boll’ (1999, and S. officinalis ‘Dwarf White’, causing textured due to larger leaves and flowers. 2003) and ‘Silver Carpet’ (1999-2001, 2003). crowding and competition. Seedlings were Consistently heavy flower production, Even with minor losses from excessive winter usually variable in habit and flower color healthy foliage and a uniform habit soil moisture, all of the cultivars of S. from the original test plants. contributed to the excellent rating for byzantina grew well, including ‘Primrose Summary Heron’. Each spring ‘Big Ears’ recovered Stachys monieri ‘Hummelo’. ‘Hummelo’ In general, Stachys proved to be exceptional quickly from winter injury to make a full looked much like S. officinalis in leaf and perennials for Northern gardens. The ground cover; whereas, the other cultivars habit but had a different flower color and a majority of taxa received four-star good were slower to regenerate, sometimes slightly more compact flower head. Stachys ratings, with only one taxon receiving poor resulting in open plots into midsummer. monieri ‘Saharan Pink’ was grown from seed, marks. Stachys monieri ‘Hummelo’ received Plant health was generally good for all so variations in flower color and habit were the highest rating in the trial based on strong taxa, but occasional health issues included observed among the plants. Stachys monieri flower production, plant health, habit quality minor chlorosis in one or more years on and ‘Saharan Pink’ were inferior to and winter hardiness. Stachys thirkei is not as Stachys macrantha and S. macrantha ‘Hummelo’ due to low flower production adaptable to average garden conditions as S. ‘Robusta’; and crown meltout caused by and variable habits and plant sizes. byzantina, but has potential in Northern excessive moisture in the plots of S. Stachys officinalis is reminiscent of S. gardens when sharp winter drainage is byzantina, S. byzantina ‘Cotton Boll’ and S. macrantha but has narrower leaves and provided. thirkei during the summers of 1999 and 2000. smaller flowers in dense clusters. ‘Alba’ and The impressive floral displays and Stachys byzantina was regularly ‘Rosea’ were comparable in habit, plant size strong habits of the green-leaved betonies deadheaded during its bloom period because and flower production to the species, compare favorably to other popular garden the heavy flower production caused a although ‘Rosea’ typically produced fewer perennials such as speedwells (Veronica), 4 Plant Evaluation Notes CHICAGO BOTANIC GARDEN Richard Hawke Richard Hawke Richard Jen Van Wagoner Van Jen

Stachys officinalis Phlomis tuberosa ‘Amazone’ sages (Salvia) and hyssops (Agastache). The fuzzy flowers of lamb’s ears add textural Hardy Phlomis interest, but deadheading is recommended Phlomis (phlomis) is closely related to Stachys but basal leaves. Plant health typically declined to maintain plant health and regenerate is an uncommon plant in Midwestern gardens. during flowering but recovered after deadheading. leaves. Selecting a nonflowering Phlomis is rarely listed as winter hardy in Zone 5, Plants were larger than Jerusalem sage at 48 such as ‘Big Ears’ or ‘Silver Carpet’ will but three Phlomis taxa were successfully grown inches tall (14 inches tall without flowers) and reduce maintenance too. Deadheading in full-sun trials at the Chicago Botanic Garden 24-30 inches wide. No winter injury was noted. betonies eliminates self-seeding, which may from 1997 through 2001. The trial included The wild-collected plants performed similarly to Phlomis russeliana, P. tuberosa and P. tuberosa the cultivated plants, but produced more ultimately crowd out the original plants. ‘Amazone’, and a group of P. tuberosa grown from seedlings. Phlomis tuberosa ‘Amazone’ is Lamb’s ears and betonies are stalwart seed wild-collected in central Siberia. All taxa reportedly a taller, more robust selection; perennials with outstanding ornamental received four-star good ratings for heavy flower however, the plants in the trial were only 4 features for a variety of gardens. Silvery production, good health, robust habits and inches taller than the species but identical in all lamb’s ears complement an array of other winter hardiness. other traits. colorful perennials as well as small roses Phlomis russeliana (Jerusalem sage) Phlomis are best grown in full sun to light such as ‘The Fairy’ or Carefree Wonder featured 1-inch long, hooded, butter yellow shade in well-drained soils. Although Phlomis (‘Meipitac’) while its rambling habit softens flowers and heavy flower production throughout russeliana grew well in the open test plots, it the hard edges of patios and walks. The June. Like Stachys, its flowers are borne in should be sited in a warm, protected site for purple spikes of betony rise above verticillasters, typically three-tiered, on leafy optimum growth. It is drought-tolerant once handsome foliage and draw attention to stems above a basal clump of boldly textured, established, but intolerant of wet or poorly their distinctive charm in perennial pubescent leaves. Plants reached 36 inches tall drained soils. Conversely, P. tuberosa is more borders, meadows and herb gardens alike. (16 inches tall without flowers) and 24-36 adaptable to average garden conditions. inches wide. Despite crown damage in two of Phlomis russeliana is a good choice for the the four winters of the trial, P. russeliana perennial border, rock garden or as a ground References received a good overall rating due to the quick cover. The delightful yellow flowers combine Armitage, A.M. 1997. Herbaceous Perennial regeneration of stems each spring. Plants were nicely with blue-flowered perennials such as Plants, Second Edition. Champaign, IL: pest-free during the trial, and were deadheaded Geranium ‘Brookside’ and Rozanne (‘Gerwat’) Stipes Publishing. to maintain plant health after flowering. and Nepeta ‘Walker’s Low’ and ‘Six Hills Giant’. Phlomis tuberosa is similar to Jerusalem sage Robust P. tuberosa is ideal for the perennial Lord, T., principal editor. 2003. RHS Plant in basic habit but has rugose green leaves and border, meadow garden and woodland edge. It

Finder 2003-2004, Sixteenth Edition. London, 1 lavender-pink flowers. The ⁄2-inch long flowers complements a variety of perennials including UK: Dorling Kindersley Limited. were borne in densely whorled clusters with up yarrow (Achillea), catmint (Nepeta) and to eight tiers per spike. Phlomis tuberosa flowered ornamental grasses. The tiered and heavily from late May to late June. Stem leaves lush foliage of phlomis add an exotic air to are similar in shape but smaller than the bold Northern gardens.

The Plant Evaluation Program is supported by the Searle Research Endowment and the Woman’s Board of the Chicago Horticultural Society.

Plant Evaluation Notes© are periodic publications of the Chicago Botanic Garden. For more information or copies of back issues, contact the Plant Evaluation Program, Chicago Botanic Garden, 1000 Lake Cook Road, Glencoe, Illinois 60022. The Chicago Botanic Garden is owned by the Forest Preserve District of Cook County.

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