JARS v41n4 - Landscapes With Rhododendron

Landscapes With Rhododendron
Clive Justice
Vancouver, British Columbia

Reprinted from "The Rosebay", Massachusetts Chapter publication

Perhaps the first call on the use of rhododendrons as a landscape plant was, in what the English chose to call, the "American Garden". Rhododendron catawbiense , R. maximum and, to a lesser extent, R. carolinianum were used along with R. ponticum in a woodland type of natural landscape consisting of mixed deciduous trees and hardy plants from the northeastern part of North America. This conceptualized American Garden was relaxed and informal, a natural appearing though contrived woodland both cool and shaded. Thus rhododendrons from early on became identified as woodland shade loving plants.
Paralleling this "natural" use of the rhododendron as a landscape plant was the Victorians' (again most exclusively English) fascination with and demand for, the unique, new, bizarre or colorful in individual plants. It was a turn of events that led to the development and hybridization of the rhododendron as a horticultural specimen plant, with almost exclusive emphasis on larger, more brightly colored flowers. These new specimens were set out, dotted or spotted in the front lawn along with the Monkey Puzzle tree, Pampas Grass and the ubiquitous Yucca. Some were grouped together in a border, but generally the individual rhododendron was used as a single isolated item.
Soon, (from the 1880's to the first war), one collected rhododendrons like one collected stamps. Good gardens were collections of choice plants and, as with horses and dogs, we strove to develop and select the best of the breed; the finest colors, the best truss, and most vigorous plant. With few exceptions, gardens were not landscapes. The worst were zoos of plants, the best, large gardens and parks which created a kind of landscape with rhododendrons naturalized or grouped as an understory of oak, beech, and pine woods.
Some nice landscapes of rhododendrons were developed using large drifts at pond or lake edges. But you don't need a choice delicate large flowered hybrid to create this kind of landscape. R. ponticum will do fine - so will 'Cunningham's White' (one of the earliest rhododendrons to be named). Both mass and naturalize beautifully as do the R. smirnowii and R. smirnowii - R. fortunei crosses. A fine example is the naturalized woodland setting in the late Leslie Hancock's nursery woodlands in Mississauga, Ontario.

Natural Landscapes
Every rhododendron collector's idea of the perfect garden for his or her rhododendrons seems to be this woodland setting. Before discussing the many types of modern landscapes we can create using rhododendrons, I'd like to mention some examples of natural rhododendron landscapes where the rhododendron is the dominant plant in the landscape. With few exceptions, these landscapes have not been adapted or used in our garden or park landscaping.
Like the late great Joe Gable's discovery in World War I, I, too, discovered rhododendrons in England, one war later than Joe's war. Unlike Joe, my interest was mainly in landscapes. The landscape that impressed me most and that I came to identify with was somewhere in the south of England; the woodlands of Hampshire, Surrey, in particular the New Forest area. Here R. ponticum edged the woodland of oaks and beeches, roads and open spaces. R. ponticum seemed the perfect edge and understory shrub. The beautiful soft color and size of flowers impressed me greatly. I've never forgotten the impression those woodlands in southern England with R. ponticum made on me. Today I still cringe slightly when I read or hear of someone damning or decrying R. ponticum as a pest. I still carry the picture of the great banks of it in full bloom. I've not been back since 1944 - it's most probably gone by now, and best kept as a memory.
Natural landscapes where R. catawbiense and R. maximum and the eastern azaleas dominate are among some of the choices to Eastern North America's mountain landscape scenery. I find the lack of interest in publicizing these fine indigenous rhododendron landscapes sad, for it is only with publicity that the public will gain knowledge and appreciation of this heritage.
With knowing comes possession and with possession, protection. The only photographs which I, as a western North American have seen of these landscapes in the rhododendron literature are from Europe. I believe we do the genus we esteem so highly a great disservice by not promoting and publicizing these great American landscapes of rhododendrons. They're equal to the rhododendron landscapes of China and the Nepal, Sikkim, Bhutan and Tibetan Himalayas. Always it seems the exotic and far away is more beautiful or more important.
The landscapes of the two western North American members of the genus, R. macrophyllum and R. occidentale , are probably even less known. On the Olympic Peninsula in western Washington state there is now probably ten times the number of R. macrophyllum than existed on that day in 1792 when Archibald Menzies and Captain Vancouver stepped ashore at Discovery Bay and found it growing with Arbutus menziesii (the Pacific Madrone) and Arctostaphylos columbiana (the Hairy Manzanita). A note for trivia collectors, these three quite diverse members of the family Ericaceae do not occur naturally in association anywhere else, except in the rather limited area of the northwest part of the Olympic Peninsula. These plants still occur together in the same spot where Archibald and George stepped ashore 293 years ago.
R. macrophyllum has greatly increased in numbers along the Pacific Coast and most particularly in the Olympic Peninsula due to logging and road building. It is among the first pioneers to grow in these logged-over lands facing Puget Sound and Juan de Fuca Strait.
It thrives on the fully exposed, dry, poor gravelly mineral soil. Some things are for sure - drainage is very good, soil nutrient is low. There is little or no organic matter, little summer rainfall, and no shade. These plants thrive, multiply and survive. R. macrophyllum goes against everything a well-behaved rhododendron should be - poor R. macrophyllum .
Everyone who has ever written about it has been wrong, or maligned it. Millais places it in the Rocky Mountains, Krussman places it in the Smokeys in eastern North America. Stevenson in the Species of Rhododendron gives the habitat on mountains at 1500 ft. altitude, and Cox places it from sea level to 1200 feet in coniferous forests. In actuality R. macrophyllum has a range from sea level along Puget Sound to 5000 ft. in the Olympics in Washington and the Skagit in British Columbia.
A landscape with R. occidentale that I like is the one in California where these azaleas become the massed base of foliage and flowers in several stands of the Big Trees ( Sequoiadendron gigantea ). This landscape, however, is one hardly adaptable to a suburban or urban garden, considering that these trees are the largest living things in the world.
Natural rhododendron landscapes, massed rhododendrons on hillsides and forests of rhododendrons, occur in Sikkim, in Nepal along the Himalayan Foothills, in the mountains above Dali (Tali) and in the Goaligong Mountains bordering the Salwin (Nujang) River both in western Yunnan Province.
These natural rhododendron landscapes also occur on the slopes and wooded area of Mount Omei in western Sichuan Province and as well in the mountains on the eastern rim of the red basin in Sichuan and again in the wild northwestern parts of this great central Chinese province.
My favorite natural landscape with rhododendrons is the sublime and picturesque vertical landscape we found on Mount Omei (Emei Shan) in the deep crevices beside the trail just below the 7 li stairway. The only other place I've seen a similar vertical landscape with rhododendron is in Scotland (this latter however, is a beautiful man-made landscape).

Planned Landscapes
The Japanese garden is a true landscape and not a garden in the Western sense of a collection of plants. The Japanese have successfully created for small sized areas appropriately scaled landscapes composed of a selection of plant material and managed to remain in appropriate scale that does not destroy the size or form of the landscape. Another reason a Japanese garden is a landscape and not just a collection of plants, is because it uses a very carefully selected and narrow range of plant material.
The rhododendron collector can also achieve this, providing he is also willing to be very selective. It doesn't matter whether the rhododendrons he chooses are trees, shrubs, or ground covers, hybrids or species, varieties, seedlings, grexes, clones, sorts or whatever. Even those having different colors, or leaf color don't really matter as long as leaf shapes are similar.
While the three basic leaf colors, yellow-green, mid-green, and dark green, can be used to increase or decrease apparent distance by gradation in a grouping of rhododendrons, the all important unifier is not the color but the shape of the leaf. As a landscape grows and develops it must present a permanent year-round picture.
Seasonal change by flowers is too fleeting (2 weeks maximum out of 52) to serve as the basis for arrangement to create the framework of a landscape. It is a great bonus but only that. Leaf indumentum also is for the zoo collector and close-up horticultural botanical viewing, it's not usually part of a landscape view. The fall coloring of azaleas and deciduous trees, too, like flowers, is a fleeting phenomena and for this reason cannot be the basic or major element that provides the unity and structure that makes a garden a landscape.
The making of a landscape for the rhododendron collector or enthusiast can be difficult for those who want to collect one of everything in rhododendrons - or one of every type of rhododendron. However, if one is willing to become selective or specialized, there is some real chance of creating a landscape using rhododendrons.

Rhododendrons As Trees
First of all, if one is not blessed with a ready source of hardy hybrids or species that have already formed very handsome small to medium-sized trees in other peoples' gardens, or that have to be moved for redevelopment to townhouses or condominiums, one has to grow one's own and quickly. There are a number of hardy rhododendron hybrids which will make fine small single and multi-stem trees from 12 to 20 feet in height. These tree rhododendrons would be multi-stemmed or single-stemmed, and each would have a natural picturesque and individual character form for trunk or trunks and canopy.
The reason why rhododendrons are rare as trees and this tree potential has not been exploited fully, has been because rhododendrons have been pigeonholed as shrubs. The connotation of leggy has sounded the death knell for many a shrub rhododendron that would, instead, make a fine small tree if grown from the start to be a tree.
Just imagine, a single large 'Cynthia' with its beautiful trunk and canopy in a patio or large tub in a courtyard. It would be picturesque, exotic, and in scale with today's smaller spaces.
What an opportunity for the rhododendron collector to mass under this rhododendron tree some small leaved mound and carpeting rhododendrons such as Polly Hill's North Tisbury and Robin Hill hybrids or Dietrich Hobbie's hardy R. williamsianum and R. repens crosses from Germany developed for the Swedish market or Warren Berg's R. pronum and R. keiskei 'Yaku Fairy' hybrids from the Pacific Northwest - all are fully hardy in USDA Zone 4, -20F. (-30C). Of similar hardiness are seedlings that will make fine trees of R. fortunei , R. decorum and R. ponticum , 'Parson's Gloriosum', 'President Lincoln', 'Catawbiense Boursault', 'Cynthia', 'Roseum Elegans' and 'Roseum Superbum' - all are hardy in USDA Zone 4.

Group Planting
What makes the large rhododendron landscape effective (man-made and natural) is the massing of many of the same variety. In the wild these groupings have been called swarms.
Our gardens today are too small for the landscapes we'd like to see using swarms of R. ponticum or R. maximum or R. macrophyllum or R. carolinianum or R. arborescens . These should now be the landscape of our public parks and gardens. A valid approach to this public landscape is where rhododendrons are grouped and massed, at the edge of ponds and lakes, along both sides of woodland trails, or billowing at the edge of broad sweeps of lawn.
These larger landscape images, however, can only be duplicated in the rhododendron collector's garden through the selection of rhododendrons that will provide a more appropriate scaled down version for the smaller space of the urban and suburban rhododendron fancier's garden. This does not always mean smaller growing rhododendrons. It can also mean rhododendrons with smaller leaves that will give a finer range of texture to the groupings.
By grouping many rhododendrons together sharing the same basic leaf shape and selecting from those rhododendrons with smaller leaf sizes, we have the basis to create rhododendron landscapes. A rhododendron landscape on a quite small scale for a 50 X 50 ft. backyard can be created with the use of the evergreen azaleas.
Those lovely Robin Hill and North Tisbury hybrids combined with the tall growing leggy and hardy ones developed by Joe Gable - a carpet of massed 'Yaku Fairy,' or 'Red Carpet', or R. racemosum can take the place of a lawn. There are carpeting rhododendrons for every climate.
Great, massed swarms of 'Blue Diamond' and 'Blue Tit' with 'Hinodegiri' and 'Hinamayo' can be backed up with thickets or copses of Triflorums - R. augustinii and R. yunnanense seedlings. The Triflorums like R. carolinianum and R. desquamatum when massed make great natural hedges and backgrounds. These also combine well with the many deciduous azaleas with the same leaf shape.
Another way to create a landscape or garden of rhododendrons is with a staging process. In Stage I, begin by planting groups of rhododendrons, each group combining varieties that have the same leaf shape. Plant them very close together so they can achieve an instant fully-clothed effect to your landscape. As these grow and stretch out, they will begin to free up the ground below.
In about 5 years, begin planting the carpeting and low-growing rhododendrons, the ones that have similar leaf shape to those overhead, along with the many non-rhododendron ground covers, like Cyclamen, Epimedium and the Asarums. These are perfect with heart-shaped and round-leaved rhododendron, while Pachysandra, Kinnikinnik and Vinca go well with many of the lepidote rhododendrons.
The dwarf and carpeting rhododendrons have not been exploited for landscaping, or for ground covers at all, always being considered as an individual plant. If they can grow massed in the wild, surely they can do the same for a garden landscape.
The culture of these second stage ground cover rhododendrons you plant now changes; these should be kept low or compact - by pinching back, even some severely by such as power pruning and mowing to create irregular carpet and natural-like masses where no plant can be singled out as an individual. Never, however, shape or make distinct by pruning the individual rhododendron plant. This kind of topiary where the individual plant is shaped into a jellybean or gumdrop is not creating a landscape and is out of place in a natural landscape.

Leaf Classification
There are 5 broad but distinct leaf shape groupings for rhododendrons.
Group One - The classic rhododendron leaf - the elliptic ovate, long oval shape of R. catawbiense , R. ponticum , R. maximum , R. fortunei , R. decorum , and R. campylocarpum . There are many examples of this leaf shape from the old Ironclads to new hybrids such as, Shammarello's 'Ice Cube' and 'Pinnacle', Gable's 'Cadis', 'Catalgla' and 'County of York', many of the Dexter R. fortunei hybrids such as 'Brown Eyes', 'Champagne' and 'Dexter's Pink'.
Group Two - The second type of leaf shape grouping is the distinct blunt tipped orbicular round and heart-shape of R. williamsianum , R. orbiculare , R. wardii , R. souliei and their hybrids, some in this leaf group are Gable's 'Henry Yates' and 'Joe Gable', Dexter's 'Scintillation', Nearing's 'Magnaglos' and 'Ramapo', Leach's 'Robin Leach' and 'Applause' and Knippenberg's 'Hardy Giant'. Usually, leaves of these rhododendrons are shiny and bright, with a leaning toward the yellow-greens rather than blue-greens.
Group Three - A third type of leaf shape grouping is the lanceolate long narrow rolled edge shapes of R. yakushimanum , R. strigillosum , R. griersonianum and the more hardy R. smirnowii , R. degronianum , R. makinoi and their progeny. Leaves of this grouping are more dull green, mainly long and narrow, usually with grey, white or tan indumentum on the underside of the leaves. There are many new hybrids of the species R. yakushimanum , such as 'Serendipity', Shammarello's Yaku Royalty series, 'Yaku Prince', 'Pinnacle' and 'King Tut'. Other hybrids include 'Ethel V. Carey', 'May Time', 'Pink Parasol' and David Leach's R. maximum album , and R. yakushimanum crosses, 'Anna Hall' and 'Pink Frosting'. The species themselves R. yakushimanum , R. smirnowii , R. caucasicum , R. degronianum and R. makinoi are all good landscape plants in this leaf grouping. There are many new hybrids with this narrow rolled leaf shape, and, when used singly, always seems to look out-of-place among other rhododendrons with more traditional leaf shapes - e.g. the old ironclads. The stand-out quality may be why they are so popular.
Group Four - A fourth leaf grouping is the oblong medium-sized leaves of the R. heliolepis , R. triflorum , R. cinnabarinum , R. carolinianum , their selections and hybrids. Leaves in this grouping are never much more than 2 - 3 inches in length " - " in width - mostly dull mid-green. These group well with the mid-sized leaved evergreen azaleas and the carpeters like R. rupicola or R. pronum . Some of the hybrids in this leaf grouping have the greatest potential for the medium-sized landscapes. Several of the selected forms of R. carolinianum album are suitable along with the many Triflorum series species and selections of R. augustinii , R. yunnanense , R. oreotrephes , R. ambiguum , R. lutescens , R. keiskei , R. triflorum and R. davidsonianum . Nearing's R. carolinianum and R. keiskei hybrids: 'April Blush', 'Ramapo', 'Windbeam' and 'Wyanokie' and the Guyincourt hybrids: 'Brandywine', 'Chesapeake' and 'Delaware' are Zone 5 hardy and belong in this medium sized leaf grouping.
Group Five - A fifth leaf form that is close to group four is the smaller privet leaf shape of the Kurumes, Indicums, Kaempferis, Obtusums and R. impeditum . The range of rhododendrons both evergreen and deciduous forming trees, shrubs and ground covers in this grouping is extremely wide. Next to the round and heart-shaped leaves of the R. williamsianum , R. wardii , R. orbiculare group two crowd, this grouping of small leaved rhododendrons offers the best opportunity to create natural landscapes for the small garden.
Beatrix Farrand, the great plants-woman and landscape architect, always used the fine textured evergreen Ilex crenata (Japanese Holly) to unify and give a continuity to her landscape plantings. So too, or why not use instead, the small leaved rhododendrons with the added bonus of the flowers, which the Ilex does not have, to provide this essential continuity to the landscape.
Some examples of the many persistent leaved azaleas in this leaf group, or Kurume type, are: Morrison's (Zone 6) Glenn Dales, those over 5 ft. tall, like 'Samite', Tango' and 'Gypsy' to the medium sized ones such as 'Ivory', 'Pippin' and 'Viking' to the low growers 'Niagara' 'Cupid' and 'Mandarin'. Shammarello's medium dwarf and hardy (Zone 5) 'Hino-white', 'Hino-pink' and 'Hino-red' also belong in this leaf group as do Joe Gable's large tall growing Gable girls, Louise', 'Elizabeth' and 'Caroline' and Polly Hill's prostrate Satsuki azaleas - 'Louisa', 'Pink Pancake' and 'Joseph Hill'.

Utilizing These Ideas
Perhaps the ideal design for a rhododendron fancier's landscape is a layout combining one or more of the rhododendron landscape leaf groupings just described, each grouping designed in a finger or pocket. These five fingers can be arranged around a central area like the palm of one's hand or pockets along an open, or pergola covered, walk or beside the edge of a grass allee. The rhododendrons within each finger or pocket would be clustered and arranged around an irregular or informal edge of a lawn, a carpet of massed prostrate rhododendrons or a pool of water. If these finger, or pocket, planting areas can be designed large enough, there could be a looped crushed stone walk incorporated around the irregular informal edges of grass, rhododendron carpet or water. Each finger, or pocket, would become a landscape display, or a community of those rhododendron hybrids and species which are leaf compatible.
The central area could evoke a real rhododendron landscape such as an Appalachian bald with one or more large glaciated grey granite boulders. These would be buried to show only the scalp of bald pate among a carpet of prostrate rhododendrons.
A theme for another of these self contained rhododendron landscapes might be a central stretch of water surrounded in whole or in part by a floating edge of rhododendrons. This would evoke yet another real rhododendron landscape, a Yunnan mountain lake.
In this ideal rhododendron fancier's garden, a series of thickets of tall growing rhododendrons would fill the interstices between the fingers forming divisions, backgrounds, transitions or frames for the landscapes but also becoming an integral part of these landscapes.
These thickets could as easily be copses of one or two of the small tree species. The multiple stems of the Trident Maples, Acer tartaricum , A. ginnala and A. griseum , the Shad-bush and the Saskatoon Berry, Amalanchier canadensis and A. alnifolia , the Snowbell Tree, Styrax japonica , the Snowdrop Tree, Halesia carolina , the Sorrel Tree, Oxydendron arboreum or the Camellia Tree, Stewartia ovata are all suitable for this purpose. Also what better place among and behind these thickets or copses to have garden service areas for compost, rhododendron seedlings and cutting frames, and small tool storage sheds all hidden from the landscape, but close at hand.

Clive Justice, landscape architect, based in Vancouver, British Columbia, has traveled extensively and designed gardens in many parts of the world.