Bulletin of the mencan Rock Garden Society VOL. 40 SUMMER 1982 NO. 3 THE BULLETIN Editor Emeritus ... Dr. Edgar T. Wherry, Philadelphia, Pa. Editor . Laura Louise Foster, Falls Village, Conn. 06031 Assistant Editor . Harry Dewey, 4605 Brandon Lane, Beltsville, Md. 20705 Contributing Editors . Roy Davidson, Anita Kistler, H. Lincoln Foster, Owen Pearce, H.N. Porter Layout Designer Buffy Parker Business Manager . Anita Kistler, 1421 Ship Rd., West Chester, Pa. 19380 CONTENTS VOL. 40 NO. 3 SUMMER 1982 Astilbes For Summer Bloom — Mrs. Ralph Cannon 105 Aruncus Aethusifolius (Lev.) Nakai: How It Got Here — Dr. Richard Lighty . 110 A Garden For Urchins — Frederick McGourty 112 Penstemons and Other Westerners in Troughs: Part III - Other Westerners — Mark McDonough 116 \J Inside The Dragon: Anatomy of a Study Weekend — Marvin Black 122 The Showy Heartleaf — Kenneth Wurdack 135 Silene Polypetala — F.C. Galle . 137 Propagation of Woody Plants, Some General Observations — James E. Cross 140 A Garden Lab — Sharon J. Collman 141 Of Cabbages and Kings 144 Cover Picture Aruncus aethusifolius — Alan P. Slack, Media, Pennsylvania Published quarterly by the AMERICAN ROCK GARDEN SOCIETY, incorporated under the laws of the State of New Jersey. You are invited to join. Annual dues (Bulletin included) are: Ordinary Membership, $9.00; Family Membership (two per family), $10.00; Overseas Membership, $8.00 each to be submitted in U.S. funds or In• ternational Postal Money Order; Patron's Membership, $25; Life Membership, $250. Membership inquiries and dues should be sent to Donald M. Peach, Secretary, Rte. 1 Box 282, Mena, Ark. 71953. The office of publication is located at Rte. 1 Box 282, Mena, Ark. 71953. Address editorial matters pertaining to the Bulletin to the Editor, Laura Louise Foster, Falls Village, Conn. 06031. Address advertising matters to the Business Manager at 1421 Ship Rd., West Chester, Pa. 19380. Second class postage paid in Mena, Ark. and additional offices. Bulletin of the American Rock Garden Society (ISSN 0003-0863). Printed by the Deer Spring Press, Norfolk, CT VOL. 40 SUMMER 1982 NO. 3 Bulletin of the rnerican en etu Astilbes For Summer Bloom Mrs. Ralph Cannon Chicago, Illinois Photographs by H. Lincoln Foster If you admire plants for their individual florescence can be appreciated. One iso• characteristics you will grow astilbes in lated astilbe will give particularly reward• your garden. They are beautiful as ing results if it is planted against a back• foliage plants and their flowers are ground of contrasting color among among the loveliest. They blossom from neighbors with bold leafage as a foil for June through August, filling the land• its ferny, much dissected leaves. A single scape with feathery spires of bloom for plant thus treated can be so attractive many weeks in summer. They are beau• that usually more than one will eventu• tiful in colonies, as companions to other ally be scattered through the garden. plants, or as solitary exclamation points, On the other hand, astilbes in large and they associate and blend well with groups will give a different effect, particu• other plants in the open, somewhat larly when foaming with their feathery shaded garden or in a woodland setting. plumes of many small flowers. When using a single plant both its pos• If you decide to grow astilbes, choose ition and background should be carefully a place in light shade, with soil rich in chosen as should its companions. A sing• humus and leaf mold and ample mois• leton should be seen from all sides so ture, but good drainage. You will find that its foliage, growth pattern and in• they are reasonably happy in full sun (if 105 kept moist), or dappled shade, but do their fibrous root systems it is possible to not do their best in dense shade. Mois• move plants at any time, even while in ture and semi-shade are the keynotes for flower, provided they are well watered success. When planting the larger stan• after replanting. dard clones and species in colonies allow Astilbes are herbaceous perennials about eighteen inches of space for each belonging to the Saxifrage Family. They plant so they may achieve their full de• are upright, bushy plants of mostly velopment. Drifts of the miniature clones medium to tall heights. They almost al• need far less space per plant: eight to ways have two-to-three-alternately- twelve inches apart should be sufficient. compound, dark green, fern-like leaves Astilbes need very little care unless having toothed or cut leaflets and pani• they become exceedingly dry in which cles of showy flowers in shades of white, case they may become subject to attacks pink, lilac-red or crimson. Each small from red spider mites. Such attacks may flower has two to three pistils and eight to be controlled by a brief, forceful spray of ten stamens. The majority of astilbes are cold water every week or so, but it is too large for the average rock garden, easier to prevent red spider than to cure but are ideal for woodlands or sited close it. to water. There are, however, a few As astilbes are heavy feeders, they species and clones delicate and small should be given an annual spring dres• enough to feature in the lightly shaded sing of compost, well rotted manure, or rock garden. good garden fertilizer, though they per• There are many species, mostly from form satisfactorily with only a natural Eastern Asia, but, because of the prop• mulch of fallen leaves. As their root sys• ensity of astilbes to hybridize and be• tems are very shallow, a mulch will pre• cause of the many years of purposeful vent heaving in winter and excessive hybridization and selection, true species drying in summer. Planting them near a are almost impossible to obtain and large stone will often ensure that the plants listed in most catalogs are of hyb• roots have enough moisture in dry wea• rid origin of confused or unknown ther. parentage. These hybrid clones, though Though astilbes can be grown from frequently incorrectly named, are, how• spring sown seed and do, indeed, self ever, extremely beautiful. Let us, how• sow in suitable locations, they are, ever, list and describe briefly the species, perhaps, most satisfactorily propagated difficult as most are to obtain. by division of the roots as they hybridize Among the taller species best suited to freely in gardens and plants grown from the large shaded or waterside garden are seed are unlikely to come true. The A. riuularis, blooming in July, with spiky, beautiful named cultivars must, of but large panicles of flowers that range course, be propagated vegetatively if from yellowish white to reddish on four they are to be true to name. Indeed, foot stems; A. davidii, a robust plant from since astilbes make quite heavy and tight China, whose rose-purple flowers in fibrous root clumps, they are benefited tight clusters on slender upright bran- by division every three to four years to chlets form a narrow panicle up to two keep the plants vigorous and floriferous. feet long on stems reaching six feet or Division is not difficult if a strong, sharp more; A grandis with creamy white knife is used. It is best done in early panicles of three feet on stems up to six spring in cold regions and in either spring feet. or fall in warmer areas. However, with Of the medium high astilbes, A. 106 japonica is, perhaps, the best known. It has been used extensively in hybridizing and is one of the parents of the many As- tilbe x rosea crosses sometimes listed as Astilbe x hybrida. The true species has pure white flowers in rather loose pani• cles on stems from one to two feet tall and blooms very early in the spring. An attractive form or hybrid named A. j. uariegata has yellow variegated leaves, while another, A. j. joins purpureis has purple leaves and stems. Astilbe astilboides, another Japanese species, sometimes incorrectly listed as Spirea astilboides or Aruncus astil• boides, grows to three feet and has dense, heavy clusters of flowers. Astilbe thunbergii, also from Japan, is about eighteen inches tall with thick pyramidal clusters of blossom. A superior miniature clone, supposedly a form of A. thunber• gii, available from a few Western mail Astilbe thunbergii 'Fijisanensis' order nurseries, is A. thunbergii 'Fujisanensis . It is a delightful little plant few astilbes with arching rather than about ten inches tall and well worth seek• stiffly upright flowering stems, a charac• ing out for the lightly shaded rock gar• teristic it frequently passes on to its hyb• den. rid offspring. Astilbe bitemata and the dubiously Astilbe rubra, from India, is also two distinct A. crenatiloba are the only feet tall and has dense panicles of rose species of this genus to be found outside flowers. Astilbe taquetii is a rigid, robust of Asia. These North American natives plant from two to three feet tall with grow from Virginia south to Georgia and bright reddish lilac flowers in a narrow west to Tennesee. They are coarse spike twelve to fifteen inches long. A plants (known colloquially as False plant sometimes known in the trade as A. Goats-beard) with rather thin panicles of 'Taquetii', supposedly a cross between a yellowish white flowers held atop stems dwarf form of A. dauidii and A. from two to three feet tall. Though this is simplicijolia, is also known as the 'Star one of the few true species readily availa• Astilbe' because of its white star-like ble (from Eastern American wildflower flowers in panicles twelve inches tall. nurseries), they are hardly worth grow• Astilbe chinensis, growing from eigh• ing, unless a particularly good form with teen inches to three feet tall, has some• larger, heavier panicles of blossom can what fluffier, much shorter panicles of be obtained.