Rhododendrons in the Modern Home Grounds
By Ruth M. Hansen, Portland, Oregon
Fig. 31. Dwarf rhododendrons, with a background of taller varieties.
C. Smith photo
The genus Rhododendron has given gardeners one of the greatest selections in plant sizes known to man. Every size of plant is represented from tiny mat-like creepers up to the heath-like lapponicum group, then on to those whose ultimate height averages from four to six feet, again another height group, those which serve best as background material reaching probably ten to twelve feet or more. After this group we are then into the trees which will attain forty or fifty feet. Last of all are the epiphytes, those lovely, fragrant and tender varieties used primarily as Coolhouse specimens. The only type of plant not represented in the genus rhododendron is a climbing variety, and who knows, perhaps that is still waiting some lucky plant explorer.
Aside from the wide range in heights, rhododendrons give us an almost complete color range. Granted, there are no true greens or blues, but the beautiful chartreuse green of R. ambiguum and R. brachyanthum and the varying blue shades of R. augustinii (Fig. 32) are ideal for blending purposes and should be used as such. There are some 700 named species and over 10,000 named hybrids and to use, say, two or three hundred of these plants requires a profound knowledge of their cultural requirements, their likes and dislikes as to exposure, sun, wind, shade and to their surrounding associates.
Fig. 32. R. augustinii in the Society Garden,
Crystal Springs Island.
C. Smith photo
In the past few years we have noted a change in the architectural design of houses, the trend now being long, low and spread out, often referred to as Ranch style. This change in house design has necessarily meant a change in the landscape design. Outdoor paved areas have now become an integral part of our daily lives to the extent that flagged and terraced areas have increased and lawns have diminished to a minimum, almost entirely in some cases. There is a greater freedom in the use of materials both architectural and plant, and one finds that the low-growing rhododendrons lend themselves admirably to our modern landscaping; as few shrubs can offer the year-round interest and beauty that is found in rhododendrons.
Landscaping any home ground calls for the grouping of plant material so that there is harmony of color and texture throughout the year. This is commonly called plant composition, though it is nothing more than the creation of beautiful pictures with living plants. The color of the foliage is just as important as that of the flower and with rhododendrons there is a vast color range, indeed a charm to rhododendron foliage. Some are remarkable for their felted indumentum on the under-surface of the leaf, namely R. fulvum, R. bureavii, and R. beanianum are strikingly beautiful when planted so that one can enjoy their added beauty. Then there are those with a green and white combination, R. smirnowii and R. yakushimanum. These are intimate plants and should be grown beside a path so the passer-by can appreciate the soft white indumentum. To my knowledge there are no other garden plants that have such glaucous, blue-green foliage as do certain rhododendrons. Plants like R. aeruginosum, R. fulgens, R. concatenans, R. artosquameum, R. oreotrephes, and a number of others are always beautiful. For garden use possibly R. oreotrephes, R. equisetum and R. artosquameum are the most readily available in the blue-green rounded leaf type. These can well be used in either a border planting in the small home ground or as specimens. R. oreotrephes is an excellent plant whether used as a specimen, an accent plant, or in a grouping. It is beautiful in flower and without flower and is a joy throughout the year.
Fig. 33. R. 'Bow Bells'
R. Henny photo
Fig. 34. R. keiskei (dwarf form)
C. Smith photo
Another important item is the new growth. Many rhododendrons produce new growth that is just as beautiful as the flowers, R. 'Bow Bells' for instance and in fact all the members of the R. williamsianum family send forth bright red growth that is perfectly stunning in a massed planting. The baby leaves of R. leucaspis change from a beautiful bronze to deep mahogany and finally the soft green of the adult foliage. Nearly all the big leaved species produce exotic looking new growths but as these varieties are not particularly suitable for the small home ground they will be passed over at this time.
The modern house seems to have been created for the use of rhododendrons, especially in the foundation planting as it is more adaptable to the use of these plants now than at any time in the past. This is due to the long lines of the house which are readily accentuated by the low-growing rhododendrons; however the window height off the ground determines the ultimate size of the material used. A few rhododendrons particularly suited for foundation plantings are: R. 'May Day', R. 'Elizabeth', R. 'A. J. Ivens', R. 'Moonstone', and R. 'Bow Bells', (Fig. 33) for a medium growing type, R. 'Britannia', R. 'J. H. Van Nes', R. 'The Hon. Jean Marie de Montague' make excellent corner ties. In the foundation planting as in the general landscaping, it is necessary to introduce other kinds of plant material to either lighten the entire effect or for contrast. Here, one can use various azaleas, daphne, kalmia, andromeda and even the delightful dwarf roses for summer bloom.
The foundation planting of a house calls for rhododendrons requiring four different exposures and the knowledge of their likes and dislikes is essential. The north and east exposures are both excellent for most all rhododendrons so the selection can be entirely based upon the kind of material used in the construction of the house and its color. Some red rhododendrons do exceptionally well on the north exposure and being on the shady side they hold their color longer. The east exposure is especially well suited for the early spring varieties. One delightful spring grouping is a planting of the lovely white R. 'Bric-a-brac' as a foreground grouping to R. 'Tessa' which is taller growing and of a pinkish-lilac color. Where windows come almost to the ground, a mass planting of R. 'Rose Elf' can be most effective. The south and west side of the house offers our greatest problems due to intense heat reflected off the house. I have found that varieties blooming before the middle of May are more satisfactory in these exposures as the chances for having wilted blooms are lessened. Some varieties which can take full sun against a house are: R. 'Unknown Warrior', R. 'C. B. Van Nes', R. 'Christmas Cheer', R. 'White Swan', R. 'Jan Dekens' and R. 'Van Nes Sensation' to name a few.
Along with foundation plantings one must not overlook the planter box. Here is an opportunity to grow a variety of dwarf rhododendrons in a very small space with a minimum of effort, the only thing required is that the soil be deep, free of lime and that the plants receive some shade during the heat of the day. Shade is not only necessary in keeping the plants from wilting but is necessary to protect the deep reds and pink colors from fading.
R. 'Jock', a pink two-bell flower, is a spreading grower and will droop gracefully over the sides of the box, so will R. 'May Day', R. 'Arthur Osborn', R. 'Goblin' and R. 'Elizabeth'. The early blooming R. keiskei, R. racemosum and R. ciliatum can also be used, in fact most of the dwarf varieties can be used successfully in a planter box if given the proper care. For low compact plants, the repens hybrids are commendable such as R. 'Carmen', R. 'Adrastia', R. 'Little Joe', R. 'Little Bill'. R. 'Treasure' and for accent a few taller growing varieties can be used as R. 'Conemaugh', R. 'Yellowhammer', and R. hippophaeoides. Even some of the more tender varieties as R. spinuliferum, whose flowers resemble small lady firecrackers, can be placed against a brick wall and the delicate tracery of its branches will give an almost vine-like effect.
Rhododendrons are also well adapted for tube use on the terrace and have been used for many years as such in England. Now that our terraces and flagged areas have increased around our houses we find it necessary to soften the effect by introducing tube material such as small flowering trees and rhododendrons. As rhododendrons grow so luxuriantly in our Pacific Northwest climate, it is suggested that the tube varieties include tender species and these hybrids of the Edgeworthii and Maddenii series which can be enjoyed during the spring and summer months gracing the terrace and then brought indoors during the winter. Recommended varieties are: R. 'Exoninesis', R. 'Fragrantissimum', R. 'Countess of Haddington', R. 'Countess of Sefton', R. lindleyi, R. polyandrum and R. crassum.
The landscaping of banks and slopes have often created a problem but they lend themselves admirably to the use of medium growing rhododendrons with a few low-growing varieties along the edges. If the bank is of considerable size then other material can be introduced to provide shade and added interest. Cotoneasters, Viburnums, and the green-leaved Japanese Maples can be used in such plantings.
The rock garden is another method of clothing banks and this gives one opportunity to revel in the beauty of the precious little jewels of the rhododendron world. Most rhododendrons, like heather, prefer growing in masses especially the dwarf species, and no planting sets them off quite like a rock garden, but a successful planting calls for drifts of a dominant color perhaps two or three, depending on the size of the garden, interwoven with drifts of blending colors. The Lapponicum group offers a range of colors from various shades of lavender to deep purple, pink, yellow and white all of which can be grown together in perfect blending and harmonious relationship. Not only is this group valued for their prolific blooms but the beautiful coppery shades of their winter foliage gives them added charm and seasonal interest. R. saluenense, R. keleticum, R. calostrotum and others are also valuable in the winter landscape as their bronzy red foliage reminds one of our native Mahonia aquifolium, Oregon Grape. Such rhododendrons as R. repens and its many hybrids prefer having their roots tucked under some cool rock and in a matter of a few years they will put on a glorious show of waxy bell-like flowers from the deepest reds to brightest crimsons.
No rock garden would be complete without the mat-like creepers as R. camtschaticum, R. tapetiforme, R. prostratum, and R. radicans which will gradually spread over the rocks and assume their form. All dwarf rhododendrons can be used in the rockery but care must be exercised to group them according to color of bloom, color of foliage and type of foliage. Scale also enters the picture, the smaller growing varieties would naturally be placed along the path or towards the front, while the taller and more leggy growers would naturally be placed among the larger rocks.
Dwarf growing companion plants should also be introduced into the rockery. Gaultheria, Leucothoe, Vaccinium, Myrsinites, miniature bulbs of species tulips, daffodils, crocus, Erythronium, etc., all add wonders to the enchantment of a rhododendron rockery.
The border planting of the home grounds requires large shrubs and offers the taller growing rhododendrons a chance to show off their beauty and usefulness. R. 'Beauty of Littleworth', R. 'Faggetter's Favorite', R. 'Mrs. E. C. Sterling,' R. 'Susan' and R. 'Gomer Waterer' are all good background plants and can be blended wonderfully well with other varieties. The background planting should also have a selection of small trees to compliment the rhododendrons. Flowering Cherries, Crab-apples, Prunes, Dogwood, Styrax, Hamamelis and Koelreuteria are all excellent trees for background use in a small garden. There are any number of medium growing rhododendrons suitable for planting in front of the larger varieties and almost any combination of colors can be arranged. One delightful early spring arrangement is a combination of pink and white with just a touch of lavender. Let Magnolia stellata serve as the white background material and R. 'Carex Blush', a medium growing spreading type with light pink fleshy bells, serve as the primary pink motif, in the foreground a planting of R. racemosum, pink again, with Narcissus 'Moonshine' or 'Thalia', white repeat. Let this be the dominate planning, now pick up the pink color further along using R. 'Racil' or R. 'Cilpinense', daffodils again or a plant of R. 'Snow Lady' to weave the white theme through the garden. To add the final touch add a plant of R. hippophaeoides, lavender color between the white daffodils and the Magnolia.
For a really peaches and cream effect one can't beat the beautiful orange shaded rhododendrons. Alone or used as groups they are outstanding and bloom after the great splash of color is past, usually towards the end of May and carry over into June. The old favorite R. 'Goldsworth Orange' is still excellent and used with R. 'Iviza' as a foreground plant makes a charming combination. Nor can we overlook the R. 'Margaret Dunn' varieties, good foliage, well shaped plants and beautiful flowers. Of the newer orange flowered hybrids, R. 'King of Shrubs', R. 'C.I.S.', R. 'Backer's Gold' and 'Lem's Goal' are all wonderful additions to our gardens. Personally, I like to use these orange colored rhododendrons as foreground plantings to the purple-leaved Prunus pissardi or P. bliriana.
Once again, other plant material should be used along with the rhododendrons and in a background planting there is a definite place for Syringa microphylla, Daphne Lilac as it blooms along with R. davidsonianum, R. augustinii and the flowering cherries thus creating a composition of pink and lavender shades. Long after these plants are through blooming they can serve as supports for some of the less rampant growing clematis and behold, they bloom again with the large white flowers of C. henryi, the soft blue of C. 'Ramona,' the lovely red of C. 'Crimson King' or any of the other beautiful clematis hybrids. Of course, none of the strong growers like C. montana, C. paniculata or C. ligusticifolia should ever be used in this fashion as they would soon kill out the new growth and bloom buds of the rhododendrons, but there is a definite use for the more delicate growers and they can be used with rhododendrons to good advantage.
Often there is need for a tie-in between a red and pink planting. Several good bi-colored rhododendrons which can serve as transition plants are: R. 'J. H. Van Nes', R. 'Raoul Millais', R. 'Rainbow', R. 'Dawn's Delight', R. 'Lady Bligh' and R. 'Louis Pasteur.' These are all medium growing varieties and can be used as foreground plants.
Occasionally one needs a hedge planting to separate or to define certain areas within a garden. For this, R. desquamatum is excellent being an upright grower, not too heavy in character and a prolific bloomer which covers itself in early April with lilac-rosy colored flowers.
Many rhododendron fanciers are true collectors and end up with a heterogeneous garden, but I find it is possible to have a well designed garden and still be a collector. To do this requires a great deal of skill in the handling of so many varieties, both species and hybrids, as the plants must be grouped according to color of bloom, size and color of foliage and general year around effect. But it can be done. Remember the ultimate goal is the creation of a beautiful picture through the medium of living plants.