Rhododendrons are among the most practical and most beautiful of all evergreen shrubs. This huge group of plants is so varied and versatile. They have a much wider variety of purposes in the landscape than the average gardener realizes.
The popular conception of Rhododendrons is – they are large shrubs with big evergreen leaves and produce spectacular heads of flowers around the first of June. They are mainly suitable for woodlands and large estates requiring expert care.
But this is only a tiny fraction of the complete rhododendron story and a distorted view.
Rhododendron Growth
Rhododendrons cover a tremendous range which includes ground-hugging mats of the following:
- Moss-like plants 2” to 3” inches tall
- Dwarf growths, a couple of feet tall, resembling heather
- Intermediate shrubs up to 15’ or 20’ feet in stature
- Trees that may reach a gigantic 80’ feet
The leaves of rhododendrons may be 2 ½’ feet long and a foot broad, or they may be so small that they resemble the needles of spruce, hemlock, or yew.
They may even be shed in winter so that the plants are naked of foliage.
Some rhododendrons like lots of shade, while others need full sun to do their best. Their blooming season extends from February to September.
Uses Of Rhododendrons
Any group of plants that presents such varied attractions offers a rich reward to the homeowner who looks into its resources for unusual landscaping opportunities.
There are rhododendrons suitable for the following:
- Hedges
- Foundation plantings
- Rock gardens
- Screens
- Shrubs
- Borders
- Woodlands
Severe climates cannot enjoy the full limits of such variety, but the possibilities for the rhododendron-growing East and Northwest regions are seldom realized.
Rhododendron “Guyencourt Hybrids”
One of the most unusual and beautiful dwarf hedges in existence can be made up of plants of a new race of rhododendrons called the Guyencourt hybrids, which have a growth habit exactly like junior-sized Japanese barberry.
These are six different garden varieties created by the breeding talents of the well-known rhododendron authority, Guy G. Nearing.
The Guyencourt rhododendrons strike a fresh note for eastern gardens. They grow to several feet and are admirably suited for use as low, informal garden boundaries in climates similar to New York City and favored sites along the coast farther north.
Their small leaves give the plants a pleasing air of delicacy and grace appropriate to their stature.
The flower clusters are as much as 3” inches across, are produced in lavish abundance, and in one of the hybrids, they are pale yellow, a coveted color in rhododendrons.
Guyencourt Hybrid Varieties
The named garden varieties are:
- Delaware – pink-tipped flowers, yellow throats; blooms after May 1.
- Lenape – pale yellow flowers in late April.
- Brandywine – rose-pink blossoms in late April.
- Hockessin – pinkish-yellow flowers; blooms in late April.
- Montchanin – clear white flowers in late April.
- Chesapeake – yellowish-pink flowers produced in early May.
Hockessin and Chesapeake make the tidiest hedges since their growth habit is a little more dense and regular.
Of course, only one variety should be used by those who want the uniform effect usually desirable in a hedge.
In fully exposed positions, the Guyencourt hybrids’ foliage tends to be scorched by the sun in bright winter weather, so partial shade is recommended for their planting position.
Rhododendron “Boule de Neige”
Rhododendrons of a more familiar type are suitable for larger hedges and screens.
With its dense, crowded foliage, the standard commercial hybrid, Boule de Neige makes a splendid hedge 4’ or 5’ feet tall with an impressive floral display of clear white flowers in large clusters in mid-May.
This rhododendron should also have some shade to forestall attacks of the lacewing fly, which lends to infest it in full sun.
It is hardy almost anywhere. The lavender-flowered Roseum Elegans make an admirable hedge of larger dimensions, suited to more exposure.
Rhododendron Hybrid “Caroline”
For a hedge 10’ or 12’ feet tall or to block out an unpleasant view, the new rhododendron hybrid, Caroline, produced by the veteran hybridist, Joseph B. Gable, is an attractive choice.
It combines a faultless habit of growth, branched to the ground with delicate, lustrous green leaves, and it has huge pale mauve flowers.
Added to that, the blossoms are deliciously fragrant. It is probably the only floral evergreen hedge plant with scented flowers available to gardeners in the more severe climates of the Northeast.
Caroline is hardy to Boston and probably in colder regions. However, it is too new to have been tested to the limit of endurance.
Rhododendron Maximum
Our native rhododendron species from the wild, Rhododendron maximum, make a handsome hedge or screen the year around when planted with an open exposure toward the north in a large garden.
So situated with a woodland or other protection to the south, it receives just enough shelter to thrive and enough light to encourage the fullest development of its fine foliage.
Rhododendron maximum grows ultimately 15’ to 20’ feet tall after many years of cultivation.
Its white to pale pink flowers, produced in early July, are small compared to the best commercial hybrids and the spring growth somewhat hides them.
In situations where the floral display is to be stressed, it can be had in early June on another robust growing rhododendron, Album Elegans, a hybrid of ironclad hardiness that produces its white flower clusters with exceptional freedom.
It grows to impressive proportions for a tall hedge or screen without the shade and shelter required for Rhododendron maximum.
Gardeners who plan to use rhododendrons for hedges should select them with special care.
There should be at least four main branches close to ground level, and the plants should be well-shaped and compact for the further dense branching needed for a good hedge.
Continued compact growth can be assured while the plants are young by pinching out the small terminal growth buds in the autumn.
Each twig so treated will produce several branches the following spring.
Most rhododendrons grow too tall for foundation planting.
In a few years, they overgrow the windows on the ground floor, and the newer one-story homes are entirely out of scale in their dimensions.
But not so the unfamiliar scaly-leaved rhododendrons, which are as beautiful in their diminutive way as are their larger brethren.
Rhododendron Racemosum
Rhododendron racemosum, a species from Asia, is a gem in the setting provided by the forefront of a house entry.
About 15” inches tall, its small glistening green leaves are borne on arching branches that support myriads of small, light pink to bright rose blossoms clustered along their ends.
This rhododendron looks incredibly well when five or more plants are placed as a group.
It is hardy to Boston, and it blossoms in mid-May when it presents an appearance of miniature elegance.
Rhododendron racemosum has been generous in bestowing its good qualities upon its hybrids.
Several of them, also eminently suitable for foundation planting, are making names for themselves with landscape architects.
Gable Hybrid Varieties
Conestoga, a Gable hybrid, is an engaging rhododendron, neat in growth and attractively proportioned, which flowers profusely far in advance of the midseason of rhododendron bloom.
Its modest stature, not much more than 4’ feet ultimately, and fresh pink flowers commend it as a welcome relief from the regimented similarity of standard foundation plantings.
Conemaugh, another Gable hybrid, is also an attractive small shrub with its pink flowers produced even earlier in the season.
Still, it may not find quite so much favor because its habit is more upright, and its small leaves are not quite evergreen. They are shed in late winter.
Rhododendron Keiskei
Rhododendron keiskei is another wild species from Asia with yellow flowers that can be very effective or badly misplaced in a foundation planting, depending on how it is used.
Planted to fill in a restricted space between two neighboring evergreen shrubs, it will prove an interesting and unusual acquisition, mainly when it produces its unique yellow flower with red anthers in late April.
It should not be used as a featured specimen because its growth is too lanky.
Of variable height, possibly 5’ or 6’ feet eventually, it can be restrained, if necessary, to half of that for practical purposes.
Rhododendron keiskei is satisfactory at the Arnold Arboretum near Boston but close to its winter tolerance limit.
Its small leaves give it an appearance reminiscent of an evergreen azalea.
Rhododendrons As Foundation Plantings
The previous rhododendrons are especially at home in foundation plantings because the added protection afforded by the proximity of a house shelters their early flowers and precocious growth from late frosts.
However, they should not be planted in a situation facing south unless there is some shade to break the intensity of the summer sun.
Reflections from a house foundation multiply the sun’s heat unseasonably early in the spring to cause scorched foliage and encourage the plants to start growing prematurely.
The ideal placement is in plantings facing north, but the east and west sides of a house can be equally successful if the plants are protected against excessive radiation of heat and light from the foundation.
The Guyencourt hybrid group and Bottle de Neige, all of the dwarf stature and described for use as hedges, are equally valuable for foundation planting.
Rhododendron Fortunei
For the open woodland in gardens as far north as Boston, one of the finest large-leaved rhododendrons in existence is available to add color, fragrance, and an evergreen effect all at the same time.
Rhododendron Fortunei, a species from Asia, is boldly beautiful with startling, soft pink to clear white blossoms, 4” to 5” inches across, gathered into trusses of about 9 flowers.
It blooms about 2 weeks before the more familiar commercial rhododendron hybrids in a dramatic cascade of pastel blossoms with yellow throats and a rich, sweet scent.
Rhododendron Fortunei is a shrub of noble proportions with an ultimate height of 10’ or 12’ feet, sometimes as much as 20’ feet.
Its handsome foliage, vigorous growth, and freedom from pests recommend it for naturalizing.
Rhododendron Discolor
For woodlands as far north as New York City, Westchester County, and similar climates, a superb, later-blooming relative of Rhododendron Fortunei can be added to the available shrubs of extraordinary quality.
Rhododendron discolor offers an abundant display of giant pale pink to white blossoms, scented like gardenias, in early July when floral contributions from other shrubs are conspicuously lacking.
The loose clusters of enormous blossoms fall in tiers of color which are much more natural in woodland than the stiff heads of blooms typical of the commercial hybrids.
This Asian species offers a spectacle of stately magnificence when a mature specimen 12’ to 15’ feet tall produces its stunning display.
Modern Garden Hybrids “Naomi Series”
For climates no more severe than that of Philadelphia, a group of modern hybrids of the highest quality is suitable for woodland planting.
The Naomi series, consisting of 11 different named garden hybrids, is everywhere conceded by specialists to be among the finest cultivated varieties in existence.
Their blossoms are 5” inches in diameter, about 9 to each rounded cluster, in colors ranging from deep to pale pink, and are mixed with cream, yellow, and chartreuse in different hybrids.
The best of the Naomi group are the following:
- Stella Maris
- Nautilus
- Exbury
Woodland Planting
Woodland planting does not mean that these rhododendrons can be placed in the dense shade beneath trees against which they must struggle in competition for food and moisture.
If they can have some watering in time of drought, they can be planted beneath the outstretched branches of such deep-rooting trees like oaks and pines, providing the shade is high and open so that there is good light and some sun.
Otherwise, they should be placed beyond the spread of overhead trees, at the edges of clearings, and in similar situations where they can have 40% or 50% percent of the day’s sun, which assures a lavish display of flowers.