Rock Garden Quarterly
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ROCK GARDEN QUARTERLY VOLUME 58 NUMBER 4 FALL 2000 tditohal As I leave the position of Editor of the Rock Garden Quarterly, I am pro• foundly grateful for all the sharing of knowledge and experience and love of plants that has enriched these pages and enriched my own life. I hope rock gardeners will always open their gardens to inspire others. I hope rock gardeners will continue to turn their attention from their own gardening to write and record for others, both beginners and the tried and true, to broad• en and deepen our understanding of our art. The torch of the editorship now passes to Jane McGary, a highly capable editor with a wealth of professional experience and a passionate plantswoman. Jane has demonstrated her commitment to the North American Rock Garden Society in many arenas. Please support her in her efforts to make the Rock Garden Quarterly ever more interesting, useful, and inspiring. —Cjwem Kelaidis COVER: Eriophorum scheuchzeri by Rhonda Williams, Wasilla, Alaska All Material Copyright © 2000 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 58 NUMBER 4 FALL 2000 FEATURES Plants of the Shale Barrens, by Martha Oliver 251 Ohio's Special Wildflowers, by Robert Henn 257 Woody Miniatures for Rock Garden Relief, by Gerald Taaffe 263 The Second Hundred: Reliable Plants for the Post-Beginner (con't.) 267 by Given Kelaidis Rock Gardens of North America: A Series 293 Jeanette Axton's Siskiyou Paradise Ed Miller's Garden Jim & Anne McClements: A Garden of the Woodland Kristl Walek's Garden Irene Klein's Garden Jerry & MaryGrace Pottmeyer's Garden Gerald & Ruth Taaffe: The Discerning Collectors' Garden Roxie & Armen Gevjan's Boundless Gardens Al & Nancy Deurbrouck's Gardens DEPARTMENTS Awards 307 Musings 312 Plant Portraits 314 250 ROCK GARDEN QUARTERLY VOL. 58(4) PLANTS OF THE SHALE BARRENS by Martha Oliver ^^Jatural rock gardens are hard to The plants of the Alleghenies live findin the eastern USA. The special on the very old bases of worn down combination of well-drained soils, mountains, on loose, crumbly shale high light levels, and scant rainfall, that may be 500 million years old, if that favors small, jewel-like, indige• the fossils tell the tale. The bedding of nous plants doesn't occur often. the rock is vertical and very well East of the Appalachian Mountains, drained. From the Gulf of Mexico the a natural rock garden occupies the area rain clouds sweep up the western side known as the shale barrens. From the of the ridges, and, rising, drop their southcentral portion of Pennsylvania, rain. By the time the clouds pass over heading south-southwest along the this ridge they are dry. Brooks discuss• eastern slope through Maryland, West es two West Virginia towns 25 miles Virginia, and Virginia, and even far• apart; the one on the western flank ther south, an area in the rain shadow receives 65" annual rainfall; the one on of the mountains has produced a set of the eastern slope between 9" and 21". plants isolated in a sort of island, cut Heat rides up those eastern slopes off from others like them by surround• from the Ridge and Valley Province, ing areas of higher rainfall and less so the area just west of Washington, severely vertical rock bedding. DC runs 4-5°F warmer than the west• Phlox enthusiast Edgar Wherry ern slope. The combination of higher explored this area in the 1930s, and heat, lower humidity, and dry condi• others, like Don Humphrey of Green tions has created a niche for a special Spring Park in northern Virginia, have set of plants that can be grown suc• followed, making notes on the charm• cessfully in the Northeast (where the ing plants of this region (see past bul• delicate plants of the Rockies fade letins). Maurice Brooks' book, The away in cultivation). Appalachians (1965), remarks on the Some of these plants are already large number of endemic species and, well known to rock gardeners. with the old-time naturalists' eye, ties Antennaria virginica var. argillicola is the flora and fauna and geology and the shale barrens pussytoes, shorter (to climate into a unified whole. 3") and tougher than the other vari- 251 eties. Phlox subulata var. brittonii, the Clematis albicoma (white-haired moss phlox of the barrens, comes in clematis) is an endemic herbaceous white, pale pink, and soft blue-gray, shrub with typical leather flowers, somehow missing the shrieking about 10" tall, and blooms in Virginia magentas and screaming fuchsias of in early April with pale yellow, hang• the cultivars available by the square ing bells. The even rarer C. coactilis foot at the local discount mega-stores. and C. viticaulis (ghost leatherflower) Penstemon hirsutus, the short-lived have fuzzy, urn-shaped flowers on a but lovely pink bearded-tongue, is plant covered with silver fuzz. They widely distributed in the northeastern form neat and persistent clumps. United States, but the paler P. can- The endemic C. viorna is a herba• escens is found in the characteristic ceous vine that will climb to 10', with places: dry, rocky, wooded slopes and the same leather bells, but these are shale outcrops from Pennsylvania to pink to brown with paler edges. The northern Alabama. Cheilanthes lanosa plant will happily romp through a (hairy lip fern) dries to crisp, brown shrub or small tree. Celtis tenuifolia fronds in its native habitat during the (dwarf hackberry) is a good support summer, but it responds to abundant for this, since it is open enough for rainfall with pleasure, remaining light to penetrate among the branches. green and flexible in the full sun it It is a small tree of the dry, rocky enjoys. The easternmost member of foothills of the southeastern US, pro• the genus, C. lanosa is just one of 125 ducing sweet, edible fruits in the early species in a genus of mostly arid sub• fall, as well as good fall color. tropical or tropical taxa. It is found on Rhus aromatica (fragrant sumac) rocky outcrops in limestone or shale. begins the year early with clouds of Opuntia compressa (prickly pear cac• small, fragrant yellow flowers, contin• tus) surprises non-gardeners by the ues with small, red fruits, and finishes elegant way it avoids the damage from the year with scarlet fall color. A freezing and thawing during the win• dwarf selection, 'Gro-low', gets no ter: draining its tissues into the stout taller than 2'. root, it lies down, resembling a balloon Other indigenous plants include from which the air has slowly escaped. Amsonia ciliata (threadleaf bluestar), In the spring it rehydrates, standing up which Wherry describes as "well- again in a matter of days, then bloom• behaved, lovely pale blue stars in late ing with disproportionately large, spring," even though it does get 2-3' poppy-like flowers of bright yellow or tall; Antennaria plantaginifolia (plantain pink atop the green, spiny, pancake pussytoes), with broad, silvery leaves pads. Paxistima canbyi (mountain lover) on a spreading plant, from open is an evergreen shrublet, never taller woods and shaly banks; and Asclepias than a foot and slowly spreading. quadrifolia, with stunning pink whorls These are easy, reliable plants that of milkweed flowers on an 8" plant in thrive with normal amounts of water, dry, upland woods. rather than turning gray and furry Aster oblongifolius (aromatic aster) and then disappearing. There are has light blue flowers in October, and other plants, however, that deserve Wherry says it is "too little known but wider use, and, even though they are suitable for the rock garden," especial• difficult to find, they can be grown ly the cultivar 'October Skies' that from seed and will make lovely addi• stays under 12". It is the foliage that is tions to the rock garden. aromatic; the plant will slowly spread 252 ROCK GARDEN QUARTERLY VOL. 58(4) to a wide mat and is easily divided. period in late summer on a plant that A plant with perhaps too many can be 2' tall. named cultivars, Chrysogonum virgini- Heuchera pubescens (shale barrens anum has good, long-blooming, yellow coral bells) has larger flowers than any flowers on short, running plants. Don of the taller species that have been Jacobs' C. 'Eco Lacquered Spider' is a used as parents in the plethora of bit too vigorous for my garden but Heuchera hybrids of the last decade. would be fine in the island bed in the Found on dry limestone ledges in par• middle of a parking lot (where I'd also tial shade, this tough plant withstands put Oenothera speciosa). In open woods dry, hot conditions and gives to all its on limestone it blooms from April to progeny the like ability. At 18-24", it is June, and often beyond, on 8" stems. taller than most small gardens can Chrysopsis mariana (Maryland gold• gracefully accomodate, but the leaves en star) prefers the dry, poor soil and are usually as nice as those of H. ameri- full sun of the barrens, producing 1" cana and often marbled beautifully. clusters of golden, single daisies on sil• Awards for charm (read: small very foliage in September and flowers) would go to Houstonia longifo- October. In rich soils it is too tall, but it lia, a bluet at 6-10", with erect branch• will stay below 12" in the hot sun and es and tiny white or pale lavender barren sand of the serpentines. flowers. It blooms in June and July in Coreopsis auriculata produces bright dry, sandy fields and on wooded orange-rayed flowers on stems 6-12" slopes.