Rock Garden Quarterly
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ROCK GARDEN yj W r? ^pm) ' - ^*«* Jifej^si^ v %.1l W:' j«aV >^ •;*> QUARTERLY •LUME 57 NUMBER 3 SUMMER 1999 COVER: Astragalus utahensis by Lori Chips, Norwalk, Connecticut All Material Copyright © 1999 North American Rock Garden Society Printed by AgPress, 1531 Yuma Street, Manhattan, Kansas 66502 ROCK GARDEN QUARTERLY BULLETIN OF THE NORTH AMERICAN ROCK GARDEN SOCIETY VOLUME 57 NUMBER 3 SUMMER 1999 FEATURES Mint Condition: Labiates for the Rock Garden, 163 by Given Kelaidis Staying Power: Summer Mints to Freshen the Garden, 169 by Panayoti Kelaidis Nepetas, by Dan Hinkley 179 Agastaches for the Rock Garden, by Richard Dufresne 185 Rainy-Season Plants of the Southwest, by Sally Walker 191 Salvias Slender and Slight, by Betsy B. Clebsch 211 DEPARTMENTS Plant Portrait: Satureja spicigera 217 Cunila origanoides 218 White forms of Hepatica nobilis 219 Musings: Rock Garden Screes 220 Seed Exchange 222 Gardens 225 Dracocephalum botryoides 162 ROCK GARDEN QUARTERLY VOL. 57(3) MINT CONDITION: LABIATES FOR THE ROCK GARDEN by Gwen Kelaidis sprig of mint may turn ordi• many do you have in your garden? nary lemonade into a sophisticated Gardeners who prefer to grow use• cooler for the summer patio—even ful—or do they really mean edible?— though Mentha spicata and M. x piperita plants are familiar with the riches of may not be the most elegant of plants. this family, which provide a large pro• So can the small species of mints con• portion of commonly used herbs, tribute a lovely garnish to the sophisti• including savory (Satureja), oregano cated rock garden. Members of the and marjoram (Origanum vulgare), mint family, or Labiatae (or Lamia- rosemary (Rosmarinus officinalis), ceae), are often thought of as rough thyme (Thymus vulgaris), basil herbs, like the two above, which are (Ocimum basilicum), and sage (Salvia invasive in the extreme in average officinalis). Perennialists have a few soils. The labiates are characterized by substantial plants in their repertoire four-sided stems (square in cross-sec• from this family, including Monarda tion), opposite or whorled, often aro• fistulosa, the fairly aggressive Ajuga matic leaves, and a corolla with two reptans, and Salvia, from the commonly lips, the upper formed of two fused distributed S. x superba to a host of petals, the lower of three. Flowers, recently introduced species and culti- from a horticulturist's view, are often vars. Agastache and Nepeta are two not very large relative to the leaf and more genera that have been experienc• plant. The seeds are often large (1-2 ing a surge of popularity (see other mm is common) and easy to germi• articles in this issue). nate, a highly endearing quality. I have never considered myself a Almost all of these species prefer to devotee of all of these plant wonders, grow in full sun. but there are nevertheless mints that I The natural distribution of the mint consider necessary to the fully devel• family is cosmopolitan, but the great• oped rock garden. I have seldom seen est concentration of species occurs in a garden that could carry through the the Mediterranean region. About 3500 seasons with just gentians and kab- species in 180 genera offer many schia saxifrages. And is there a single opportunities for cultivation; how garden in North America where only 163 true alpines are grown? I strive to have sometime in the late 1980s. It is diminu• a garden with some plant in flower tive in stature, reaching a mere inch or from the earliest snowdrops of maybe three. The flowers are a pale February until the frost takes the lavender in many-flowered, dense, ter• vibrant red zauschnerias in the minal whorls. Grape-purple bracts add autumn. But merely flowers are not a deeper hue to the inflorescence. The enough; the garden needs to have stems form a mat from a few inches to a interest throughout the year. This is foot wide, bearing 5-7-lobed, adorable achieved partly through use of plants lea\ 2S with blades about a centimeter with evergreen or eversilver, durable long and about equally wide. They foliage. This is actually a feature that have short hairs that give the foliage a distinguishes the perennial garden soft gray sheen over the basic-green from the rock garden: most plants of color. The foliage has a pleasant minty the perennial border die back to the fragrance when bruised. ground in winter (garden phlox, del• This plant is particularly happy and phiniums, asters, baby's breath), also felicitous in its effect when placed whereas most plants of the rock gar• above a rock, where it can drape over den retain their foliage throughout the the stony surface. However, the cloak year (silver saxifrages, drabas, creep• of foliage will likely be killed in severe ing phlox, thymes, veronicas). There weather. The mat will, nevertheless, follow descriptions of a few mints that recreate itself in the next season. Very will help bring your garden into prime good drainage will please this species. foliar condition. It has self sown freely into the gravel at the base of our rock garden, but not Stachys nivea (photo, p. 202) elsewhere. Dracocephalum botryoides is This is a charming foliage plant one of those happy-go-lucky plants with very rugose, lanceolate, tongue• that are easily taken for granted. Yet, I like leaves of dark green splayed out would be sorry to discover that I had on the ground in a flat, basal circle. lost it all. I am delighted to report that The very large (as much as 4 cm long), it is happy in my sandy rock garden as white flowers rise on short stems in well as in the heavier soil of my late May. I have grown this in moder• Eudora Street garden. ate conditions, in clay-based soil, In central Asia there are several where the same plant has persisted for other species of Dracocephalum closely ten years, remaining in place without related to this one. We had the delight• increasing or diminishing. It makes a ful opportunity to try D. paulsenii, with great foil for any small, gray foliage, even smaller leaves and flowers of such as Eriogonum ovalifolium or blue, but it departed after two years. Veronica caespitosa, or even woolly We have just planted out D. palmatum, thyme, or with a yellow-green foliage which looks very similar to D. botry• such as Gentiana gelida, Hacquetia epi- oides but has deep blue flowers. It is pactis, or one of the apple-green culti- worth trying to sort out the species as vars of Sempervivum. This plant should they become available, looking for the tolerate most rock garden conditions, choice little mat-formers. although I haven't tried it where it experiences severe drought. Nepeta phyllochlamys Despite the disparagement that this Dracocephalum botryoides species suffered in the last issue of the This plant came into circulation Rock Garden Quarterly, I consider it a 164 ROCK GARDEN QUARTERLY VOL. 57(3) lovely plant. It was originally collected this species captured my interest years on the 1977 MacPhail and Watson ago, with its charming round leaves expedition to Turkey. The heart- about 2 cm in diameter. All parts of shaped, cordate-based leaf blades are the plant have long, woolly hairs, but about 1.5 cm wide and 1.0 cm long, they are less dense on the upper sur• smaller when grown in harsher condi• face of the leaf, and thickly tufted tions, larger when grown in some along the gently toothed margins. The shade. Both sides of the leaves and the leaf margins are upcurled towards the stems are covered with woolly hairs, midrib, and the inner (upper) -most, resulting in a silver overlay to the new leaves are curled across from each green leaves. Miniature, clear-pink other in twin circles of green rimmed flowers are a bonus to the foliage in with warm silver. Each plant may early summer. The leaves have a sharp reach to 40 cm across, rather large for scent similar to peppermint. the rock garden. I grow M. rotundifoli• This plant looks great with semper- um in a hot wall and cut it back hard vivums or lewisias, and it would be in the fall—or whenever it overruns fun to combine it with something neighboring plants. maroon, such as a ruby sempervivum, This is another plant that shows off the deep maroon winter foliage of in the rain. It looks equally good in the Delosperma nubigenum, Armeria mariti- heat of summer under the blazing sun. ma 'Rubrifolia', or the blood grass, or Place it near a plant of dark green the forest green of Santolina 'Small foliage, such as tansy or a dark Nancy' or even Teucrium chamaedrys. Santolina. Yellow tulips are an attrac• The leaves look great with dew or tive accompaniment, picking up the raindrops pearled on their leaves. golden overtones of the hairs, while Nepeta phyllochlamys is at home in blue flowers, such as Penstemon nitidus the sandy crevices of a hot, southwest- or blue dwarf bearded iris, or blue flax facing wall, making a lovely band of take up the current fashion of blue and rounded, almost bead-like leaves held yellow. strongly curved under along the It is easy to propagate Marrubium cracks of the flagstone. It will self-sow rotundifolium from shoot cuttings. This in the garden. I consider it one of those species was introduced by Zdenek plants that never needs propagation to Zvolanek, who collected seed on Ala maintain it in the garden; rather the Dag in Turkey. gardener has the ability to remove any plants that have placed themselves in Lamium armenum and inauspicious places, while keeping Lamium eriocephalum those that look great.