Over a century ago, the word “rhododendron” was a name touched with magic, conjuring up images of mansions framed in priceless shrubberies, the utmost in beauty and exclusiveness. Today that magic is slowly fading from the name.
What has happened? A wild shrub, Rhododendron maximum, with leaves resembling garden rhododendrons but with ungraceful stalks and disappointing flowers, has been sold by the millions under this enchanted name.
Actually, it is a rhododendron, so there can be no charge of fraud. But there is nothing magical or even desirable about this wild shrub. So, for many people, the name rhododendron eventually brought to mind a picture of that inferior rhododendron rather than the magnificent race of hybrids.
But a new era has dawned for the East as it did long ago for the Pacific Northwest. Rumors have long been brought to us by those who travel in the south of England, Wales, or along the western coast of Scotland.
Superb as are the older garden hybrids compared with their wild relatives, a still more wonderful group has been in the making – actually many groups – though only the forerunners of the first were ready for planting by 1952.
Emergence Of The Dexter Rhododendrons
The new rhododendrons do not render those we have less beautiful or less beloved, nor shall those yet to appear. If you have a fine specimen of one of the better sorts and take proper care of it, it will remain 50 years hence a landmark and a sight to marvel at.
Much like the rose and iris, new varieties do not efface the choicest of the old but rather supplement them.
Nor will the best of the new kinds come upon us in one big flood. Instead, it involves the painfully slow work of hybridizing, the growing of millions of seedlings, the rejection of hundreds of thousands as unworthy and unfit, and the watching of an eventual few selected for their superior qualities, while frigid winters and torrid summers thin their ranks.
For, sad to say, the most spectacular cultivars of all are most often the least hardy.
Separating The Proverbial Wheat And Chaff
The cultivars so long rumored were bred for milder climates. All that work of breeding and all the waiting had to be done over for gardeners of the northeastern states. Meanwhile, those who live along the Pacific are already enjoying the glories we anticipate.
Back in the early 1950s, we were deluged with unnamed seedling hybrids, rejected but not destroyed. These continue to be offered under the name of Dexter hybrids. Most of them aren’t hardy. Initially, few were even as good to look at as the rather frowsy wild rhododendron from the nearby hills.
Out of perhaps 20,000 Dexter seedlings that have outlived their originator, Charles O. Dexter, perhaps 20 or 30 superb ones were selected during the following two or three years by a group of expert judges. These few were then propagated and given appropriate names.
Sadly, it proved presumptuous to attempt any early estimate of the best individual plants while gardeners awaited said decision.
While a large proportion of the Dexter seedlings proved utterly worthless, many did possess some merit. But, unfortunately, the best of them ended up so close to the final few chosen that their judges faced many a difficult decision whether to accept or reject a given plant.
Of these borderline cases, some were named and propagated by enthusiastic owners. In contrast, others had enough public support to become the Dexter and Cowles rhododendrons we know today (the Cowles varieties being closely related).
Therefore, it would be foolish to condemn all the unnamed Dexter hybrids still appearing each year without qualification. But before you buy any of them, take this advice: Select them while in flower and make sure that they have passed at least one winter and one summer in a climate as severe as your own.
Their original home on Cape Cod is on a par with the shores of Long Island and southern New Jersey, much milder than at the same latitude a few miles inland.
The Gable Rhododendrons
Meanwhile, Joseph B. Gable started his breeding about a year before Charles 0. Dexter with approximately the same parent species. He selected the few best plants among his thousands of seedlings.
These have been in the hands of propagators for several decades now, and 1952 saw the introduction of ‘Caroline’ (not to be confused with the utterly different Rhododendron carolinianum, AKA Rhododendron minus var. minus). ‘Cadis’ and ‘Disca’ soon followed, both named offspring of Caroline.
How do these new varieties differ from the best of the older ones? Many new are cultivars slowly shaping up every year, some large, some small, some very dwarf.
Others may be blooming with shapely hells (i.e., dense, bloom-covered thickets) which droop on long stalks, some with a flaring calyx colored like the petals, and in the dim distance, numerous sorts vaguely defined.
There are starlets, yellows, and shades of salmon and orange, many of them still years away, so far as our colder climates are concerned.
The Oriental Parentage Of Modern Cultivars
The hybrids we’ve seen the past few decades come chiefly from a group of Chinese and Indian species bearing huge fragrant flowers with marvelous modeling in shades of delicate pink and satiny white. Primary among these species, in both date of discovery and size of flower but last in hardiness, is Rhododendron griffithianum from Sikkim.
It has been known for over 150 years but is slow to flower, challenging to grow, and prone to pass its lack of hardiness to the offspring. Each flower in the enormous cluster may spread to 6″ inches across. The palm of an adult’s hand is roughly 3 1/2″ inches wide; therefore, both palms side by side would only slightly cover this one floret.
A decade after R. griffithianum was discovered, Rhododendron fortunei was brought from Eastern China. Though some specimens are not at all winter hardy, the hardiest can be grown north of New York City. Up to only 4″ inches across, its florets still could not hide behind a single palm.
The floret has a satiny texture with edges peculiarly puckered and remarkable modeling. The upper lobe is tilted back while the two lower ones sweep forward just enough to give it a grace unique among its kind. The habit of the plant is sturdy and treelike.
At the turn of the century came Rhododendron discolor, with Rhododendron decorum from western China arriving a little later. Both resemble R. fortunei but with larger flowers up to 5 inches, a shrubby rather than tree habit, and thicker, deeper green leaves.
Still another species, Rhododendron auricalatum, has fragrant flowers, pure white with a greenish throat much like those of a lily, opening in midsummer.
The Problem With These Species
None of these species is entirely satisfactory as a garden plant, even where they’re hardy. The flowers do not usually come all over the top of the shrub as we like to see them, but a few clusters are borne down among the leaves. During some years, no flowers appear at all.
Anthony Waterer, who was hybridizing in England over a century ago, set as his model something between Rhododendron catawbiense from our own southern mountains and Rhododendron ponticum from southern parts of Europe.
Both are shapely shrubs, well clothed with handsome foliage and bearing dome-shaped flower clusters high above the leaves. By substituting more desirable shades for the weaker purple of R. ponticum and the harsh magenta of R. catawbiense, he gave us many of the best varieties we still cherish.
The Great Challenge
If the larger and more graceful flowers of the fortunei group could be transferred to the hardier, shapelier plants of the catawbiense group, what a rhododendron we might have! And that is precisely what the first wave of new hybrids in the 1950s was, at least in part.
‘Caroline’ is a large shrub of remarkable vigor with clean, bright foliage densely massed and an abundance of great flower trusses (clusters) every year.
‘Cadis’ is superior to ‘Caroline’ in the detail of its flowers, which tend toward the seven lobes of the fortunei group. However, they also have some of the edge frills of R. caucasicum.
The leaves of both ‘Cadis’ and ‘Disca’ show more of the quality of R. discolor, their other parent. All three flower in pale shades, nearly white.
The Ridgewood Cultivars
Using a cross between R. griffithianum and R. decorum with pollen from some of Waterer’s best red hybrids, I obtained a striking cultivar, prevailingly bright rose with a large maroon blotch in the throat and somewhat fragrant.
These were dubbed the Ridgewood hybrids, and propagation of four of the best was soon underway. ‘Beatrice Pierce’ was the first to reach the public through Donald L. Hardgrove. These Ridgewood hybrids resemble some of the Dexter hybrids, many of which had similar parentage and are hardy in northern New Jersey.
One of the most remarkable specimens among these hybrids to open its flowers in this climate undoubtedly has R. griffithianum in its ancestry though the label has long been lost. It put out a cluster 9″ by 11″ inches of florets averaging 4″ inches wide; the color is apple blossom pink with a yellow throat, and it is sweetly fragrant.
Another cultivar, not so far advanced as the large-flowering one but still quite desirable, is founded on Sikkim’s Rhododendron campylocarpum, a medium-sized shrub with yellow bell-shaped flowers.
In more than a century of cultivation, this has given but a single hybrid, ‘Goldsworth Yellow’, which lays any claim to hardiness. While this persists north of New York City, it makes unsatisfactory growth and does little flowering.
‘Lady Primrose’ will grow on Long Island, as will probably ‘Moonstone’, both having some tint of yellow. Yellow and apricot shades appear in the Dexter hybrids, too, but are mainly associated with inferior foliage.
‘Moonstone’, with a neat, dense habit derived from its other superb parent, Rhododendron williamsianum, will probably stand as the role model for new hybrids, from which hardy forms will eventually appear.
Ongoing Goals
Most sought after (yet still elusive) is a hybrid of really scarlet and perhaps orange shades derived from Rhododendron griersonianum, Rhododendron haematodes, Rhododendron dichroanthum, and similar species. The colors are there but neither hardiness nor really satisfactory habit.
Nurseries offer both old and new reds from Holland, some untried, while others tried and found wanting long ago. Many prove reliable on Cape Cod and Long Island, in southern New Jersey, and perhaps along the Delmarva Peninsula.
Unfortunately, to really test a rhododendron variety takes not 2 to 3 years but 2 or 3 decades. For the present, the best dependable reds are the old Anthony Waterer hybrids with their not too brilliant crimson.
Still far away are such possible parents of species as Rhododendron nuttalli, distantly related to Rhododendron carolinianum but with flowers larger than Rhododendron griflithianum; Rhododendron sinogrande, with leaves as long as your arm; and others less spectacular – though perhaps more potentially useful in landscape planting.
Breeding can go on for hundreds of years more before these possibilities are exhausted.