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Journal American Rhododendron Society

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


Volume 19, Number 2
April 1965

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"Visit to Laurelwood Gardens"
The Home of Mr. and Mrs. John F. Knippenberg
New York Chapter Notes, February 19, 1964 by Betty Hager, Secretary

        An enthusiastic group of members met at Schrafft's in New York to visit, by way of an excellent slide program, beautiful "Laurelwood Gardens," the home of Mr. and Mrs. John F. Knippenberg.
        Following are some of the taped comments of Dorothy Knippenberg: "Our thirty acre woodland was begun 44 years ago. Great effort has gone into the preparation of the area and many tons of topsoil, sand, and humus are constantly being worked in as new areas are being cleared and existing nurseries replanted. The naturally hilly woodland is dominated by towering Canadian Hemlocks, a wonderful wind protection for our rhododendrons. Two ponds have been dug and a natural spring-fed brook meanders through the lowland and is surrounded by interesting rolling terrain, with declining Northern slopes that have been thinned to provide a congenial home for the many classes of rhododendron hybrids and species that are constantly being added. Our woodland is located in hardiness zone 6A. You may also be interested to know that in 1960 the entire thirty acre garden was presented to the township of Wayne and will become a public rhododendron park following our lifetime. For this reason we are trying to assemble masses of the hardiest varieties. (Our slides are arranged in sequence of bloom.)
        Come now and visit with us our many colored dwellers of our woodland - the days are lengthening, it is late March, as we eagerly examine the swelling buds, with color already showing on early Magnolias and R. mucronulatum. When Star Magnolia blooms, it coincides with R. mucronulatum, whose arrival signals the end of winter, with her delicate flurry of rosy-lavender blossoms. Willowy and rugged, this rhododendron has been a favorite for generations and a large specimen is an exquisite sight. The largest specimens in this planting are about 4 feet high, planted about ten years ago, with some doubt as to their survival due to the hot dry location and no water available, only rain. Certainly proof of their hardiness and adaptability, the memorable picture is more impressive every year. The clonal 'Cornell Pink' form blooms for us about one week later, an appealing tint of pure clean pink. It silhouettes beautifully against the green of the foliage of rhododendrons.
        From the beginning, plant breeding has been an unfailing fascination and lively interest at Laurelwood. Due to the pure color and hardiness of 'Cornell Pink', it naturally became a favorite parent. Here is a happy combination, a cross of R. 'Bric-a-brac' x 'Cornell Pink', called 'Snow Maid', due to her early bloom. A neat, slow growing, compact shrub with completely evergreen foliage, similar in appearance to 'Bric-a-brac'. The flowers arc a large clear, apple blossom pink, with prominent pink stamens. When Magnolia soulangeana blooms, R. schlippenbachii takes over the spotlight with its profusion of pink and pure white blooms, as lovely a sight as could be desired, unfailing and dependable.
        One of our earliest to bloom is 'Rosa Mundi' an old caucasicum hybrid, much admired for her dense compact habit. Her flowers are pale blush pink, growing in full exposure here, but she prefers just a little more shade. She is surprisingly hardy for us. A similar hybrid 'Christmas Cheer' resembles her closely.
        The superior Gable hybrid, 'Pioneer' is a most prolific bloomer, and one of the few rhododendron that excel in full sunlight. It's hardiness, vigor, and adaptability have been inherited from its parent R. mucronulatum. It is brilliant pink and very showy against the still bare winter landscape. In addition to having multiple flowered terminal trusses, it blooms as well in the axils of the leaves all along the stems. It's very easy to grow and valuable for filling a gap so early in the season. 'Pioneer's' winter habit is semi-deciduous.
        'P.J.M.' is a very hardy hybrid that blooms at the same time and is fully evergreen. It takes on marvelous shades in the winter, rich plum purple, altogether different from its green summer dress. The very early, bright violet flowers show off dramatically against the still purple-tinged winter foliage. A worthy addition and dependable grower, it thrives in full sun.
        Another mucronulatum hybrid is 'Conewago', a cross of carolinianum X mucronulatum, which extends the blooming season another ten days. Easy to grow, and of endearing character, the large 1½" florets are a pastel lavender pink. For early bloom, all the 'Jacksoniis' are indispensable. The Gable selection, 'Jacksonii #5' a cross of R. caucasicum x 'Nobleanum, shouldn't be hardy and the young plants are not, but when they reach a mature size they show unexpected adaptability, and come in late April along with R. hippophaeoides and R. keiskei and manage to escape frost. We can expect a display of the char rose pink blooms every year. For this beautiful show, she was rewarded in late November with a half pail of apple pomace, spread gently about her roots, not over the ball, but near the feeding roots. I think this may be beneficial, have been using a great amount of it from a cider mill, and will report on it again. 'Jacksonii #6' blooms later and has a large truss, deep brilliant red, that is quite pure. It's long leaves and foliage resemble 'Atrosanguineum' somewhat, as if it might be a relative.
        What could be more rewarding than a large drift of that most obliging Nearing hybrid, 'Ramapo'? One of the few truly hardy dwarfs for the small scale garden, suited to a prominent place in the rock garden, or foreground, wherever it's gem-like individuality can be appreciated at close hand. It is a rich violet blue, best seen here in an open position, shaded lightly from the noonday sun. This is a northern slope. 'Ramapo' is of remarkable interest in winter when its leaves during late December suddenly take on a deep metallic, hazy purple winter hue that remains until it blooms.
        Early every May we rejoice and are indebted to Joe Gable for Azalea 'Springtime', a very hardy plant. Usually in bloom about the fifth of May, the large single blossoms are very clear pink. It is recorded as an F. hybrid and is a cross of poukhanense X kaempferi. In the distance the pink rhododendron in bloom is R. metternichii. As mid-May approaches, the whole landscape sings, when an endless variety of azaleas bloom. We can expect a good performance from most of the Kurumes and Kaempferis planted here. With native dogwood as the background, the picture is really beautiful - such as 'Snow', 'Rose Greeley', 'Hino-crimson', 'Morning Glow', 'Glory', and the Kaempferis such as 'Fedora' and 'Othello'. The exquisitely scented varieties azalea, 'Corsage' has misty lavender blossoms, like orchids poised on strong stems. It is one of the best background azaleas, to tone down too much color and to add distance to the scene. 'James Gable' is surprisingly hardy for us, an exciting deep vermillion, even more brilliant than 'Hino-crimson . 'Louise Gable' is one of the most beautiful of all the double hardy salmon pinks. It adds two weeks to the azalea pageant. Another extraordinary Gable introduction, beautiful in all stages of opening bud, like miniature rose buds, 'Rosebud' never fails us. We grow three forms. One form was introduced by Koster Nursery, one is called 'Lorna'.
        A common native azalea in our woodland is R. nudiflorum. Although sparse blooming in the shade, when planted in the open, it gives a good account of itself. R. keiskei is best grown in an open location with the roots shaded from the hot sun. It is completely hardy with us at a large size, but if you have small plants, grow them in a nursery as they often bark split when young.
        Blooming long before its hardy parent, 'Boule de Neige', 'Laurel Pink' is our own creation, almost ten years old. A cross of 'Boule de Neige' x R. catawbiense x 'F. C. Puddle' the flowers of good substance possess a lacelike delicacy. Twelve florets per truss form neat pink balls of bloom late in April-it's a handsome small shrub all year and completely bud hardy. R. racemosum, very desirable and unexpectedly hardy, it's small leaves silvery white beneath, blooms early in May in a burst of beauty from clear pink to pinkish white. In its native Himalayan Mountains it flourishes on craggy hillsides - here it enjoys a location surrounded by rocks. 'Windbeam', a very endearing plant of refinement and character, is easy to grow in any location. Here it is growing in full sun. It is very hardy as these plants bloomed perfectly after a recent winter when the thermometer at our place plunged to sixteen degrees below zero. It is a continuing joy all through the winter months and the foliage is highly aromatic.
        We imported our plant of R. metternichii, F.C.C. form, from England in 1955. It is a grafted plant, a choice ornamental, hardy species from Japan. The long narrow leaves are felted beneath while the flowers are a clear rose pink. It is worth growing for foliage alone. 'Boule de Neige' is a superlative plant at all times. Around the tenth of May you can expect a fine display of delicately frilled snow white flowers. Magnificent in habit, growth, and foliage, for early blooms it is second to none. In an attempt to produce a hardy yellow, we crossed 'Boule de Neige' x 'Hawk' (R. wardii x 'Lady Bessborough'). Shown here is one of the first of the cross to bloom - an intermediate shade, as expected when a white rhododendron is crossed with a deep yellow. By either self -pollenizing this flower, if it will take it's pollen, or re-crossing the two best of the group, we should be able to come up with a yellower color, more the color of wardii and still have the compact hardiness of 'Boule de Neige', if enough seedlings are grown. Yellow is recessive and difficult. We are always trying to obtain a deeper color in a hardy compact plant is recessive and difficult. We are always trying to obtain a deeper color in a hardy compact plant.
        Early in May, the exotic griffithianum hybrid, Jean Marie de Montague', blooms a bright scarlet red. A plant breeder's inspiration, we pamper her to make use of her aristocratic pollen. We often cross her pollen on a red hardy hybrid like 'Atrosanguineum' or 'Kettledrum', and we should have some good colored things coming along soon. We move this plant in winter into a cold frame as it seems that by just covering it with glass and closing the sides, with no heat at all, we are able to winter the flower buds. In the open at our place, the foliage will burn badly and most winters the flower buds will only open partially, or not at all.
        We have a group of 'Conestoga' seedlings, a cross of carolinianum and racemosum. All these plants are very fine and vary from white, to pink, to peach, and make wonderful background plants. We crossed 'Conestoga' with hanceanum annum, a species of the Triflorum Series, a compact shrublet under a foot high, with flowers of pale creamy yellow. The result was a quite compact little plant, but the yellow is rather recessive again. It is a pretty thing, and surprisingly hardy.
        On a hillside we raised 6000 Dexter seedlings and are now removing plants as they bloom well and have some unusual trait. A very pretty plant is 'Blush Button'. The button is where the stamens should be - the stamens have reverted to a ruffle of petals, resembling a button in the center. 'Caroline Gem', another of our own hybrids, had Gable's 'Caroline' as the seed parent, crossed with the deep red 'Elizabeth'. This interesting hybrid of conveniently small dimensions resulted. Unusually lustrous leaves are its outstanding virtue. As would be expected, the intermediate rose-red shade of the color is about half-way between the lavender flowers of 'Caroline' and the vivid scarlet red of 'Elizabeth'. By carrying this into the second generation, we could hope for a scarlet of the same compact habit. The species makinoi, a very hardy species of the Ponticum Series, blooms later than metternichii which it resembles. The recurved leaves are very long and narrow with a thick wooly suede on the lower surface. The feathery appearance of its exotic leaves create a dramatic oriental effect when planted near a pine.
        'Sappho', an old Waterer hybrid is a very striking white, heavily blotched, but temperamental, as 'Sappho' only survives with us and isn't hardy enough unless we put her under glass in winter. I believe this could be crossed with some white form of catawbiense and the blotch may come out. Another old Waterer hybrid, the deep red griffithianum 'Mars', is astonishingly hardy for us, and blooms every year. The almost-white stamens add to the beauty of the wide open flowers, but 'Mars' is not as vigorous a grower as we would like. We have crossed this in many ways and our seedlings are beginning to bloom.
        Around the middle of May, the Dexter garden comes into bloom. For some years we have been growing and testing a large quantity of numbered as well as named Dexters. Among them is the 'Scott #I' and 'Wissahickon' (originally Morris #3). 'Wissahickon' is a sun-splashed carmine that lights up the woodland with its dazzling glow. A numbered Dexter 12507-5 is a combination of many colors, rosy-red with cream-colored center, and it's blotched creamy peach. Another, 12507-2, is a bright pure glistening scarlet, startlingly blotched with black, but the blooms are not dependable with us. Dr. Wister's plant winter-killed, so I believe we are the only one to have this. It seems to be a fine plant for use in breeding, even more red than 'Jean Marie de Montague'. The flowers remind me of 'Essex Scarlet'. 'Scintillation', introduced by our keen evaluator, Paul Vossberg, is one of the hardiest, with dark green foliage, ideal plant habit, large trusses of luminous pink and excellent substance. For us, 'Scintillation' prefers light shade. Not as hardy in New Jersey is 'Mrs. W. R. Coe', a deep brilliant pink with crimson throat.
        'Oleander' is another of our own selections from the Dexters, with upstanding trusses blush to white - this is a "mule," has no stamens, so couldn't be bred, but has a very heavy substance flower. Another Dexter, 109, is outstanding in color, floriferousness, good plant habit and hardy. James Wells introduced 'Avondale' (formerly 12507-6), a fine red, but a flat truss and not reliably hardy for us. 'Westbury' is a lively pink selection with golden sparkle and has behaved well in our trials. A Dexter grown on the West Coast is 'Ramona' - it has immense flowers and has wintered at our place, but has been reluctant to set any buds after one heavy crop, so I can't report further at this time. Extending the season another week is the Dexter 12500-4, a very heavy bloomer that has never failed us, creamy white with prominent blotch, beautiful in foliage year round. We are propagating this.
        A planting of 'Cynthia' bloomed in our woodland after minus 8 degrees of winter frost. It is a very old hybrid not expected to be hardy and blooms on the north side of a very large hemlock. Does require some protection or the foliage will burn. As they get older, they seem to have less foliage burn.
        'County of York', a Gable cross of 'Catawbiense Album' X 'Loderi', is a large flowered creamy white of rich satiny texture, very plant hardy for us, but we lose some flower buds in some winters. As the plant matures, you don't get the new growth coming up with the flowers.
        Another of our own, 'Hardy Giant', a cross of fortunei x fictolacteum, has been growing in our woodland for ten years. Although the temperature has dropped to sixteen below zero one winter, this specimen has never shown any winter injury and never lost a branch. But that winter it did lose it's flower buds, as did many of our Ironclads. The flower truss is almost the size of my head, huge creamy bells with raspberry. The leaves on this plant are from 12 to 15 inches long. The young shoots as they come out are almost as attractive as the flowers, they are cinnamon colored. This is a cross made by Don Hardgrove who gave four plants to Guy Nearing, and Guy Nearing shared this plant with us. We were in doubt if we would ever see this plant bloom, and were excited when it set bud and bloomed. It seems to be very hardy.
        We made a cross of 'LaBar's White' x 'Azor' and obtained a large family of seedlings. Some bloom when white catawbiense blooms and some in June when 'Azor' blooms. All are surprisingly hardy, vary in color from pink, to salmon, to deep pink.
        An interesting cross is (R. carolinianum x R. roseum) x R. carolinianum also crossed with 'Conestoga'. A remarkable family resulted. We tried to capture the delicious clove fragrance of the roseum azalea in evergreen form. We didn't get that elusive quality but we did extend the blooming season another two weeks beyond carolinianum bloom. Some have very large trusses in shades of pink and peach, as well as the vivid clear deep pink bloom of roseum. One seedling is very curious because it resembles roseum azalea entirely even to the leaves, except they are evergreen. However, no fragrance. We would like to suggest the plant breeders use some of the pure yellow and reds of the deciduous azaleas and cross them either with the small leaved lepidotes or the elepidotes. We crossed azalea 'Klondike' with 'Boule de Neige', and the cross took. We have a very interesting group of seedlings coming along. Some are completely deciduous like 'Klondike' and some are compact and low growing like 'Boule de Neige'. They may bloom this year.  I feel we may be able to get some deeper yellows in our rhododendrons by using some of the brilliant shades by this method-it's a new field to experiment with.
        We raised 4000 seedlings of 'LaBars' White'. Try raising seeds of this, interesting things result. The seed was open pollinated, and about 10% were pure white. Our select form was the finest of these seedlings, the largest truss, almost a pure white, buds are pure white, too. Only the stamens show a little pink. It has an excellent plant habit. It is very difficult to root.
        (Mrs. Knippenberg showed a collection of Ironclads.) 
        From June 15th to June 30th, the macrantha azaleas lengthen our season - 'J. T. Lovett' is four feet wide, but only a foot high. Another azalea that blooms the first of July for us is 'Hakatashira', a very compact white, said to be a tender plant - but for us it seems to be quite hardy and never fails to bloom. Another late bloomer, 'Balsaminaeflorum', does very well for us, only the rabbits love it, and will eat every flower!
        As fall approaches we have the beauty of the Enkianthus, the Oxydendron, and in late fall we prepare our beds with humus and cow manure for the spring planting. Snow covers us.'


Volume 19, Number 2
April 1965

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