Logo for the Journal American Rhododendron Society

Journal American Rhododendron Society

Current Editor:
Dr. Glen Jamieson ars.editor@gmail.com


Volume 5, Number 4
October 1951

DLA Ejournal Home | QBARS Home | Table of Contents for this issue | Search JARS and other ejournals

Hardy Azaleas at Lindum Gardens
Irving B. Lincoln

        A new interest and a great interest is constantly being shown in azaleas, both deciduous and evergreen. Their ease of cultivation, their dependability of blooming, their hardiness, and the blazing colors in their annual Spring Show is winning for them a larger and more permanent place in our gardens. There is a wide variety of shapes, sizes, types, and colors of azalea plants so that they fit into a wide variety of situations and uses. There are tall growing varieties; low spreading varieties; evergreen varieties and deciduous varieties; early varieties and late varieties; varieties that will stand full sun and those that like part or all shade.
        Many of the varieties can be used can be used both for house plants as house plants and some varieties and garden plants. Many varieties are especially adapted to the small garden. And no other shrubs produce every year, year after year, such a mass of blooms in such a riot of colors and beauty of flower. They really lift a garden out of the commonplace.
        But very little has been written or recorded about the quality and hardiness and adaptability of the different varieties or respective tests and ratings given so that it is difficult to write an authoritative article on these choice plants. Compared to the mass of information printed about rhododendrons, that available about azaleas is meager. However, from the experience I have had in Lindum Gardens and the information gained from other sources I will give a brief description of the different types and varieties of azaleas, tentative unsupported by tests though it may be.

New Hybridizing
        Considerable hybridizing is being done to improve the quality and hardiness of azaleas but tests of the hardiness and quality -with published ratings for the different varieties have not been carried on to the same extent as with rhododendrons. Therefore, we have to take the opinion of growers of the different varieties. Hybridizing of evergreen azaleas has been carried on in the Eastern United States. In England the hybridizing of deciduous azaleas has been extensively done. And in Holland new hybridizing is being done to improve the color and size of the flowers of the hardy 'Malvatica' x kaempferi hybrids and the Vuykiana azaleas.

'Malvatica' X kaempferi Evergreens
        This new group of showy, hardy plants from Europe is being given a larger place in our gardens. It is considered by some the best hybrid of recent introduction. They have small persistent leaves and the different varieties vary in height and spread but the larger ones will reach a height of over 4 feet and spread of five feet or more. It is a rounded open shrub that will stand pruning as it gets older. In color the flowers range thru the different shades of pink and salmon and rose and orange and red. They have comparatively large blossoms, which have a diameter of 2 to 3 inches and in Spring the plants are a solid mass of flowers.

R. 'Pink Treasure'
    Fig. 34:  R. 'Pink Treasure'.  An azalea of
    excellent merit growing at Lindum Gardens.
    Lincoln photo

        They are rated among the best of azaleas and many of the varieties have been given two stars by the Royal Horticultural Society of England. Last Spring I visited some of Portland's finest gardens in the garden clubs visit. One of these 'Malvatica' azaleas was the showiest plant in one of the rock gardens. It was in the shade near a porch and gave forth its full brilliance. In our own rock garden I have several varieties. I well remember seeing a 'Pink Treasure' making a fine show in the shade with its clear shining pink for nearly a month. In full sun the blossoms are apt to fade and not last as long. The best effects from this variety is in part shade because their flowers fade in strong sunlight.
        In making this fine hardy group of azaleas, 'Malvatica' (a hardy obtusum hybrid) was crossed with the Japanese azalea kaempferi also hardy, sometimes called an obtusum variety. It grows wild in the mountains of Japan to a height of 8 feet and is semi-deciduous. The Kurume azalea 'Hinodegiri' is also used in some of the crosses. These crosses give several fine varieties.
        'Pink Treasure' is my favorite. It is pure, clear, shining pink, a real gem. The plant is a trifle lower growing than the other varieties and has a two star rating. (Fig. 34)
       'Fidelio' and 'Fedora' are more of a salmon pink or phlox pink, while 'Kathleen' is a little deeper in shade, more of a rose pink or rose red. This also is one of my favorites. 'Othello' is another variety - an orange red or porcelain rose. 'Amy' is a deep orange red. 'Betty' is a deep orange pink with darker shadings.
       'John Cairns', is low growing and spreading and good for a ground cover. Its leaves are a bit larger and more persistent than some of the others. It is a blood red or Indian red. 'Martha' is a dwarf spreading plant with shiny leaves and orchid-pink flowers shaded orange.
        Many of these 'Malvatica' x kaempferi hybrids inherit the small leaves of Kaempferi that are semi-deciduous.

'Malvatica' X kurume
        This group is closely allied to the Kaempferi group but the influence of the Kurume Hybrids give them larger, more shining and more persistent leaves and a more compact bush. 'Orange Beauty', a 'Hinodegiri' x kaempferi cross, is early flowering with beautiful trusses of large flowers, salmon-pink with orange shading. A mass planting of these azaleas puts on a show in the spring that will be long remembered. They do better in part shade as their flowers fade in full sun. Also, their early buds or blooms - are apt to be touched by a late frost. All in all it is one of the very best of the evergreen azaleas, though possibly not quite as hardy as the straight 'Malvatica' x kaempferi plants. It is one of the finest for hedges and mass planting.
        Another new variety from Holland that is destined to take a large place in our gardens is 'Addy Wery'. It is a cross between 'Malvatica' and the kurume 'Azalea Flame'. It is similar in habit to 'Hinodegiri' but its foliage is larger in size and of a rich green glossy texture. Its flowers come in mass profusion-a true blood red, without a trace of magenta or pink or purple. It should also be a little more hardy than 'Hinodegiri'. It was given an Award of Merit last year by the Royal Horticultural Society after trials in their garden at Wisley. They describe it as dwarf and compact and very free flowering, five petals, blood red on orient red with a dull orange-bronze flush. When this variety becomes well known it should be even more popular than 'Hinodegiri'.

Vuykiana Hybrids
        This group in hardiness is in between 'Hinodegiri' and the 'Malvaticas'. One of the hardiest and most popular is 'Palestrina' a pure white with a small green spot. It is hardier than Ledifolia alba and by many preferred. The plants that I have are more vigorous in growth than the 'Malvaticas' and have larger leaves. They make a very fine shaped bush. Other varieties are 'Mozart', a clear, silvery pink. 'Schubert', a deep pink. 'Mrs. Vuyk Van Ness' is light Bengal red with a deep red center. It's fringed straight up growing flowers are 2 inches across.

Kurume Evergreens
        The now well known Kurume azaleas were developed in 1818 in Japan from the wild azalea Obtusum, variety Japonicum, found at an elevation of 3000 feet on volcanic Mt. Kirishima in the extreme southern part of Japan at a latitude the same as northern Mexico and Charleston, South Carolina. It is rated as hardy in the Rhododendron Year Book. But many of the hybrids are damaged by a real cold winter in Portland, although other varieties like 'Hinodegiri' wintered very well.
        These azaleas were introduced to this country between 1915 and 1919 and their profusion of blooms in a myriad of bright colors and their shapely bushes rapidly won for them great popularity both as house plants and garden plants. They are so well known that I will not describe the different varieties. Among the best ones are 'Apple Blossom', 'Cherry Blossom', 'Daybreak', 'Pink Pearl', 'Snow', 'Coral Bells', 'Hexe', and 'Hinodegiri'.
        The Chinese azalea simsii, a later, low growing, spreading plant with large flowers has several forms. The ones available here are 'Gumpo White'; 'Gumpo Red'; and 'Gumpo Fancy'.
      'Hinomayo', one of the best evergreens, is an Obtusum, variety 'Amoenum', but in most catalogues is listed as a Kurume. It has a two star rating.
        In the Eastern States hybridizing is being done to get finer flowers on hardier plants. Mr. Morrison of the U. S. Dept. of Agriculture has developed the Glenn Dale Azaleas for the Washington D.C. Area south through Virginia.
        Joseph Gable has developed more hardy, hybrids that will match the hardiness of the 'Malvatica'-kaempferi azaleas in certain varieties.

Exbury Evergreen Azaleas
        At the Rothschild Estate in Exbury England; they have developed a new strain of evergreens that deserve recognition. So far so few plants have been introduced here that first hand information is not available. Their hardiness has not been published.

Deciduous Azaleas

        In brilliance and range of color these plants rank at the very top in the annual Spring display. They are free blooming and never fail to put on a fine show. At Lindum Gardens there is a continuous bloom for nearly two months with early and late varieties. They range in color-red, orange, yellow, gold, white, copper, pink, bronze, crimson, mauve and variegated. First come the Mollis, then the occidentales and then the Ghents and late double varieties.

Ghent Hybrids
        Only one hundred and twenty-five years ago, in 1825, a baker in Ghent, Belgium started making crossings of deciduous azaleas. He crossed the native European azaleas with Eastern North American varieties. Other varieties from Western America including R. occidentale and varieties from Asia including R. mollis and R. japonicum were latter crossed and re-crossed with the original crosses until it is now impossible to trace the parentage of either Ghents or occidentale hybrids. The so-called hardy Ghent hybrids are real hardy and will stand our coldest climates. Most of the Ghent varieties have flaring honeysuckle shaped flowers in brilliant colors coming in great profusion, slightly fragrant and latter than the Mollis or occidentale. They have a wide variety of strong colors both in true colors and variegated forms. They are red, orange, yellow, light yellow, white, copper, bronze, pink, crimson, mauve and purplish red and others.
        'Unique', 'Coccinea Speciosa', 'Gloria Mundi', 'Nancy Waterer' and 'Bouquet de Flore' I consider the five best but others are rated equally as high. 'Unique' is a tall growing plant with large clusters of flowers, bright orangeyellow, very striking in appearance, just like a real ripe orange in prime condition, a magnificent azalea. 'Gloria Mundi' and 'Coccinea Speciosa' have flowers that are almost alike but the shape of the plants are different. The flowers are orange and red with yellow markings, darker in shade than Unique and blooming later. 'Gloria Mundi' is a wide spreading plant whereas 'Coccinea Speciosa' is more rounded and a little taller, with leaves a little larger. 'Nancy Waterer' is a bright golden yellow with lighter markings-a bridge into the new Knaphill azaleas. 'Bouquet de Flore' is a late blooming, low growing plant, with bright pink flowers with lighter stripes, one of the very finest. 'Davisii' is a very hardy creamy white with a yellow eye. Others blooming here are 'Pallas', an earlier red; 'Narcissiflora', a tall light yellow; 'Fanny', a rose pink; 'Dr. Chas. Bauman', a blood red; 'Ignea Nova', a carmine red; 'Sang de Gentbrugge', a dark crimson; and 'Raphael de Smet', white and rose.

Fragrant occidentale Hybrids
        This group of plants is of particular interest to the Pacific Coast because our native azaleas from Southern Oregon has been crossed with the Ghent azaleas and others to form one of the most beautiful and fragrant groups of plants. Their colors are softer than the Ghent or mollis hybrids. The flowers are larger and more abundant than those of our natives, and the masses of blooms in large clusters have a wider range .of colors-each variety true to its color and time of bloom.
        There are six varieties each having a two star rating given by the Royal Horticultural Society. 'Irene Koster' is the first to bloom in the Spring and the most fragrant. It is a soft, lovely, bright pink, loaded with flowers every year. We have a hedge 'Irene Koster' that is greatly admired by our visitors every Spring. Following 'Irene Koster' come 'Magnifica' and 'Graciosa', a little darker in shade with a more contrast of colors-creamy pink with orange and yellow markings. 'Superba' is a deep pink with a yellow and apricot blotch. Also late is 'Exquisita', a light pink and creamy white with yellow markings. One of the finest 'Delicatissima' is creamy white with yellow and orange shade.
        All of occidentale hybrids are fragrant.

Mollis hybrids
        The mollis sinensis or mollis japonicum group of azaleas was developed by crossing the Chinese azalea mollis with the Japanese azalea japonicum and other varieties. They have large, bright, fiery, colored flowers that come in clusters. They do not grow as tall as the Ghent types but range in height from 3 feet to 6 feet. They are hardy, sturdy plants that stand full sun. In color they range from light yellow and cream through the fiery orange-reds to pink, and apricot and salmon and variegated and blotched. I have twenty-five of the best varieties, all given high ratings by the Royal Horticultural Society. Many of them are very outstanding.
        There is 'Adriaan Koster', a clear, pure, light yellow. The largest flowered mollis hybrid is 'Mrs. Van Noordt', a clear salmon-pink. 'Dr. M. Oosthoek', 'Kosters Brilliant Red', 'Kosters Dark Red' and 'Speks Brilliant' are four of the finest reds. Practically all of the mollis reds have a little orange tint which is inherited from japonicum which has an orange blotch. 'Kosters Dark Red', however, has very little orange in it. It is the nearest to a clear red that I have been able to find. The other reds given are orange-red. 'Dr. M. Oosthoek' is a large bright salmon-orange-red with a luster to it. It stands up well in the sun and the plant is a vigorous grower.
       'Christopher Wren' has large trusses of fine deep yellow flowers, orange in bud. 'Kosters Yellow' is a clear light yellow. Evening Glow is the largest and finest red-a glowing orange-red. 'Prof. Amundsen' is a soft rose with a red border and a yellow blotch, very distinct. 'Golden Sunlight' is as its name implies - a rich golden yellow, considered in Holland on a par with 'Adriaan Koster'. 'Alice de Steurs' is a yellow overlaid with pink with a red orange blotch.
       'Lemonora' has a variegated flower, apricot and rose, a fine shaped plant and one of the best. 'Queen Emma' is a companion of 'Lemonora'. It is salmon tinted orange. 'Floradora' and 'Hamlet' both are large flowered with a deep red blotch. 'Floradora' is bright salmon-orange and 'Hamlet' is salmon with sharper contrast between the salmon and the large dark red blotch. 'C. B. Van Nes' is fiery orange-red. 'Clara Butt' is a large flowered deep salmon-pink. 'Mrs. Oliver Slocock' is a tangerine suffused with terra cotta.

Double Ghent And Mollis Hybrids
        These hardy, early flowery, sweet scented azaleas are very charming. The flowers are smaller than mollis but they are double. The plants are bushy. I have six of the better varieties. 'Il Tasso' is the first to bloom. It is a soft rose-red tinted salmon. It is followed by 'Norma' which is similar in bush and flower only a little brighter in shade. 'Corneille' is still a little latter and taller growing. It is covered with small apple blossom colored rosettes-white with streaks of pink and red. It is charming, distinct and beautifully dainty. 'Aida' is still latter-the first part of June. It is lower growing and bushy and the rose tinted lilac flowers are very long lasting. 'Freya' is a nankeen yellow-tinted salmon-orange. All of the above have a one star rating. 'Velasquez' is a transparent white and a transparent cream.

Hybridizing Of Deciduous Azaleas
        Some hybridizing is also being done to get larger, brighter flowers and better shaped plants in deciduous azaleas.

Knaphill Azaleas
        Several nurseries in England are making great strides in improving the strain of deciduous azaleas. They are striving for larger flowers in finer colors. They are getting a wider, flat flower with a long slender trumpet shaped neck to give lasting qualities. Hybridizing apparently started at Anthony Waterer's Knap Hill nursery as far back as 1874. By 1925 they began propagating named varieties. Development of these Knap Hill varieties was carried on further by W. C. Slocock's nursery and at Rothschilds Estate in Exbury.
        It is claimed that these new strains are a great improvement but there are so few of the plants of blooming size in the Pacific Northwest that comparisons cannot yet be made. I have a few of the named Knap Hill Azaleas which appear similar to the Ghent Hybrids-there is a yellow very much like Nancy Waterer. Others are like the Occidentale Hybrids or a mixture of the two. An unsuccessful effort has been made to get a stock of the named varieties. Both John Henny and myself have seedlings of the Ex bury Azaleas but they have not yet flowered. I understand that some other nurseries here are starting other Knap Hill seedlings that have not yet bloomed. We are looking forward to the results.

Planting and Culture
        Azaleas require the same acid, humus soil as rhododendrons. They like a porous, peaty soil but will grow in any soil that is lime free and well drained. Most azaleas are sun loving plants and hardier in winter where their summer growth is ripened by the sun. They like plenty of water and good air and water drainage and will stand the strongest winds if not laden with ocean spray. In full sun and not too much fertilizer they make a short compact growth with plenty of twigs, tipped with flower buds. Deciduous azaleas need very little commercial fertilizer. Too much fertilizer stimulates rank growth, large leaves, water sprouts and fewer buds. The long sprouts need to be cut back and made to branch out.
        Like most surface feeding plants, Azaleas like a porous soil with air in it, plenty of water during the growing, bud-forming period, but no stagnant water to drive the air from the soil around their roots.
        In producing or maintaining an acid soil, aluminum sulphate or sulphur or a mixture of both is beneficial, although if plenty of peat moss, compost and leaf mold are used in the soil, it will be naturally acid. Aluminum sulphate acts immediately, but sulphur takes a little time to become available. Rotten sawdust is good as a mulch, but' if it is mixed with the soil, it uses nitrogen from soil during its decomposition and this should be replaced or you will get stunted growth and yellowish shaded leaves, especially on the rhododendrons. Ammonium sulphate or ammonium phosphate are good to replace the nitrogen taken by the decomposition of the sawdust.
        The soil should be in good mechanical condition, open, crumbly, friable, not stiff and pasty. If the soil is too light and sandy to hold moisture it should be replaced or improved with woods soil, leaf mold and peat. Likewise if it is too heavy and compact clay, it should be replaced or loosened up with vegetable matter, and porous, humus soil. Leaf mold, also, is the finest food for azaleas, especially when mixed with the soil in planting.
        Azaleas are surface rooters and feeders and should not be planted more deeply than they were in the nursery. A light mulch of rotted leaves applied in the Spring will keep the roots cool and moist in the summer and protected in winter, They can be planted at any time after the flower buds have set in the early Fall until they are in full bloom.


Volume 5, Number 4
October 1951

DLA Ejournal Home | QBARS Home | Table of Contents for this issue | Search JARS and other ejournals