THE EFFECTS OF AIR POLLUTION ON RHODODENDRONS
BY FRED R. DAVIS
Man's activities in producing energy, manufacturing goods and disposing of waste materials result in releasing pollutants into the atmosphere which may alter plant metabolism and induce disease. Air pollution damage to plants has been known for several decades. Its extent and importance, however, increased with the world's increasing population, industrialization and urbanization.
The air pollutants which cause plant injury are primarily gases, hut some particulate matter or dusts do affect vegetation. The gases which cause widespread damage are sulfur dioxide, nitrogen dioxide, ozone, hydrogen fluoride and peroxyacyl nitrates. High concentrations of or tong exposure to these materials causes visible and sometimes characteristic symptoms (e.g., necrosis) on the affected plants. Dosages of these pollutants (less than those that cause acute damage) may suppress the plant's growth and productivity due to the interference with plant metabolism. The purpose of this article is to describe pollutant sources and their effects on plants.
The sulfur oxides are common atmospheric pollutants which arise mainly from the combustion of fuels. Solid and liquid fossil fuels contain sulfur, usually in the form of inorganic sulfides or sulfur-containing organic compounds. Combustion of the fuel forms about 25 to 30 parts of sulfur dioxide to one part sulfur trioxide.
Sulfur dioxide may cause acute or chronic leaf injury to plants. Acute injury: produced by high concentrations for relatively short periods, usually results in injured tissue drying to an ivory color; it sometimes results in a darkening of the tissue to a reddish-brown. Chronic injury, which results from lower concentrations over a number of days or weeks, leads to pigmentation of the leaf tissue, or gradual yellowing, or chlorosis in which the chlorophyll producing mechanism is impeded. Both acute and chronic injury may be accompanied by the suppression of growth and yield.
Acute injury apparently affects the plant's ability to transform absorbed sulfur dioxide into sulfuric acid and then into sulfates. At high rates of absorption, sulfite is thought to accumulate, resulting in the formation of sulfurous acid which attacks the cells. The amount of acute injury depends of the absorption rate which is a function of the concentration. Different plants vary widely in their susceptibility to acute sulfur dioxide injury. Some species of trees and shrubs have shown injury at exposures of .5 ppm for seven hours, while injury has been produced in other species at three hour sulfur dioxide exposures of .54 ppm and, still others, at eight hour exposures of .3 ppm. From these studies, it appears that acute symptoms will not occur if the eight hour average concentration does not exceed 3ppm. However, sulfur dioxide concentrations from .05 to .25 ppm may react synergistically with either ozone or nitrogen dioxide to produce moderate to sever injury to certain sensitive plants. Rhododendron and kalmia show damage at exposures of .5 ppm for eight hours The damage consists of bleaching of the interveinal tissue and some chlorosis of the leaves. Chronic plant injury results from the gradual accumulation of excessive amounts of sulfate in leaf tissue. Sulfate formed in the leaf is additive to sulfate adsorbed through the roots and when sufficiently high levels accumulate, chronic symptoms, accompanied by leaf drop, occur.
It has been suggested that sulfur dioxide might suppress growth and yield without causing visible injury. One investigator reported that yields of rye grass grown in unfiltered air were significantly lower than similar yields of plants grown in filtered air. No visible symptoms of injury were observed.
Sulfuric acid mist which may occur in polluted fogs and mists also damage leaves. The acid droplets may cause spotted injury in wet leaves at concentrations of .1 mg/meter 3
We must all be aware of this molecule and its adverse effect on vegetation when its concentration reaches .05 to .2 ppm (annual mean). At these concentrations, one generally observes chronic plant injury and excessive leaf drop.
Nitrogen dioxide (N02) is produced from oxygen and nitrogen in the air by hot combustion sources such as open fires, furnaces, and automobile combustion chambers. Nitrogen dioxide in concentrations of 2 - 3 ppm causes bleaching of plant foliage similar to that caused by sulfur dioxide. There is evidence that at even smaller concentrations it suppresses the growth of some vegetable plants.
This substance is not as severe a pollutant as some other man-made molecules, since during rainfall it dissolves in the water to produce nitric acid which gives rise to soluble nitrates that are beneficial to most plants.
Ozone (03) is one of the most widely occurring air pollutants and one of the most destructive to plants. Ozone originates from the ozone-rich stratosphere by vertical winds. It may be a by-product of photochemical reactions between nitrogen oxides and plant producing terpenes, particularly in conifer forests. Ozone is also produced from the activities of man and his civilization.
Exhausts of automobiles and other internal combustion engines are probably the most important sources of ozone and other phytotoxic pollutants. Tons of incompletely burned hydrocarbons and are released into the atmosphere daily by automobile exhausts. in the presence of ultraviolet light from the sun, the nitrogen dioxide reacts with oxygen and forms ozone and nitric oxide. However, in the presence of unburned hydrocarbon radicals, the nitric oxide reacts with these instead of ozone, and, consequently, the ozone concentration increases. Ozone, too, can react with certain unsaturated hydrocarbons, but these products, organic peroxides, are also toxic to plants. The noxious fumes produced by automobiles and other engines are swept up by' warm air currents from the earth's surface rising into cooler air above where the fumes are dissipated. However, during periods of calm, stagnant weather, an inversion layer of warm air is formed above the cooler air and this impedes the upward dispersion of atmospheric pollutants. The pollutants then are trapped near the ground where after sufficient build-up they may seriously damage living organisms.
Ozone causes mottling and chlorosis of leaves that is confined primarily to the upper leaf surface. The spots may be small or quite large and may vary in color from bleached white to tan, brown or black, depending on the plant and on the severity of injury. In some plants, such as citrus, grapes, pine, yews and broadleaf evergreens, ozone injury causes premature defoliation and stunting.
Ozone enters leaves through stomata. Once in the leaf, it concentrates in the palisade layer where it causes collapse and bleaching or discoloration of the palisade cells. Ozone primarily affects expanding leaves, but not very young or mature leaves. Several mechanisms by which ozone can damage plants have been suggested, including inhibition of mitochondrial activity, destruction of the permeability of the cell membrane, inactivation of auxin, and inhibition of protein synthesis and photosynthesis. Although each of these effects has been observed in at least some of the hosts affected, it is not clear how ozone brings these about.
Plants can be protected from ozone damage in several ways. For example, plants escaped damage from ozone when they were watered with ascorbic acid (presumably an inhibitor of oxidation in cells); also, certain antioxidants and antiozonants such as dithiocarbamates provide some protection. In addition, some plant varieties are considerably more resistant to ozone injury than others
Hydrogen Fluorides and Fluorides
Fluorides are emitted from stacks of factories and are spread by diffusion or carried by air t;urrents. Hydrogen fluoride (HF) is very toxic to plants, e.g., corn, peaches and tulips, where Injury is caused by concentrations as low as .2 to .2 parts per billion (ppb). Fluoride accumulation in foliage generally injures the leaf margins of dicotyledonous plants and tips of leaves of monocotyledon plants. Injured areas turn tan to dark brown, die and may fall from the leaf. Plants differ in their sensitivity to fluoride. 'The more tolerant ones are able to accumulate much more fluoride (up to 200 ppm) without showing necrosis. Instead, they develop a slight chlorosis, followed sometimes by premature defoliation. Actively growing plants, particularly when their leaves are wet, are generally more susceptible to fluoride damage. Fluoride seems to be absorbed by the leaves through the cuticle and translocated to the leaf margins and tips. When a toxic concentration is reached the cells from the epidermis collapse and die. Fluorides may also escape from the plant through volatilization and washing, and the plants may recover from chronic fluoride symptoms within a couple of months. The author has witnessed very sever fluoride damage to evergreens in the neighborhood of an industrial plant which manufactured fluorides for catalysts. This type of damage is irreversible.
Peroxyacyl nitrate is produced from the exhaust pipes of cars, with ozone, nitrogen dioxide and probably other oxidizing substances in the presence of sunlight.
Peroxyacyl nitrates cause a plant disorder known as 'silver leaf' which produces spots on the lower leaf surfaces of the plants of many herbaceous crops. The color of the spots may range from bleached white to bronze. The silvering or glazing of the lower leaf surfaces injured by peroxyacyl nitrates results from air filling the space created by dehydration and shrinking of the mesophyll cells. Meanwhile, the guard cells become congested and the epidermis cells collapse.
Peroxyacyl nitrate injury has been observed primarily around metropolitan areas where large amounts of hydrocarbons are released into the air from automobiles. The problem is particularly serious in areas such as Los Angeles and New Jersey where the atmospheric conditions are conducive to inversion layer formation. Many different kinds of plants, vegetable and ornamental, are affected by peroxyacyl nitrates.
Carbon monoxide (CO) is a gas produced by incomplete combustion of carbonaceous material. All internal combustion engines produce this gas. The amount produced is a function of the temperature and oxygen supply, with well tuned engines producing less than improperly tuned engines.
Carbon monoxide injury involves foliage damage and poor plant vigor. Some pines, particularly white pine, will lose their needles when carbon monoxide injury occurs.
Man has to learn to control air pollutants so that there can be an improvement in the quality of life. Epidemiological studies clearly indicate an association between air pollution and health effects of varying severity. Air pollutants have produced both acute and chronic injury to many species of plants accompanied by suppression of growth and yield.
Some of the material in this article was taken from reports issued by the U.S. Dept. of Health, Education & Welfare (Public Health Service), 'Air Quality Criteria for Sulfur Oxides', (February, 1969).
Fred R. Davis is a chemist with a PhD. in physical chemistry from Kent State University. His avocation is raising azaleas and rhododendrons. with an emphasis on nutrition. He is also interested in breeding for disease resistance. Dr. Davis is a member of the American Rhododendron Society and the American Horticultural Society
SNAP YOUR RHODODENDRONS CLOSE-UP
BY DR. JAY SLAVITZ
Photography can be an invaluable tool for the rhododendron grower as well as a means of expanding the pleasure which these beautiful subjects can provide. It is quite simple to obtain good photographs of an entire plant or group of plants in a garden setting, but initial attempts to get good close-up photos of a single truss are often disappointing. The techniques involved in close-up or 'macro-photography' however are quite simple to master and it is this type of photography that this article is about. We will attempt to assemble an ideal camera set-up which will handle this type' of photography easily. If the camera which you already have is different from what we describe don't despair. Most cameras can be adapted to this type of work easily and give very satisfactory results.
First, the camera: The prime consideration in choice of camera is the least technical. it must be one that is easy and comfortable for you to use. If the camera is cumbersome or difficult for you to use, you won't use it. The next factor would be how close can the camera focus or be made to focus. It should handle the range between 12 and 18 inches for our purposes. Few cameras 'off the shelf' will focus in this range. Most of the simpler cameras on the market focus only to 3 feet. Better cameras focus as closely as l8 inches. We focus closer by moving the lens outward or away from the film plane. Therefore our closest focusing distance is mechanically limited by how far we can extend the lens. If we could remove the lens and extend it further out we could focus much closer. We will discuss how this is done later on, but for now the ability to remove the lens or 'lens interchangeability' is a factor we should consider when selecting our 'ideal' camera.
The next factor in camera selection is the viewing system; what you see when you look through the viewfinder as compared to what the film 'sees'. Many cameras have separate viewing and taking lens systems so what you see and what the camera sees are slightly different. At the distances which most pictures are taken, five feet and beyond, this difference, or 'parallax error': doesn't matter, but at the distances which we will be working, the error becomes considerable, to the extent that the subject we neatly frame in our viewfinder may not show up on the film at all. What we would like, then, is a viewing system which lets us see exactly what the film sees. This we find in the type of camera called a single-lens reflex or SLR, for short. By lucky coincidence most SLRs also feature full lens interchangeability, which we had stated as requirement number one.
The only other major consideration, then, is film size or format Although single lens reflex cameras are available in a wide variety of film sizes, the vast majority are built to take 35 millimeter film. Any specialized requirements not withstanding, 35 mm would be the format of choice, considering the tremendous amount of equipment available in this size as well as the ready availability of numerous film types or emulsions
The camera type described with its normal lens in place will probably focus to about eighteen inches. To get closer we will have to extend the lens further forward than its mounting would allow. To do this then we will remove the lens from the camera and place spacers or extensions between them. These extensions can be either rigid tubes of varying lengths or a continuously-varying bellows, much like that seen on folding cameras of long ago. Both work equally well but my choice would be the bellows because it allows greater variability in its extension.
The choice of film type is next and with 35mm, the choice is endless. Because so much of the beauty of our subjects is dependent upon color, rhododendrons and color photography are almost inseparable. The only exception as I see it would be the special requirements of publication. By far, the majority of 35mm color is in the form of transparencies or slides. They are inexpensive, easy to store and transport, and ideal for display to large groups. It is also possible to have good prints made from slides if you have the need The color in all films represents a compromise, none are absolutely accurate. One type may emphasize reds, another, greens etc. A suggestion would be to try different types and then settle on one or two which render colors most pleasing to you.
Although color perception is mostly subjective, it is possible to obtain objective near-accuracy by using print film. The techniques involved are not difficult but do go beyond the scope of this article.
Having then settled on the hardware, the major consideration must be the light. It is my feeling that the most dependable, consistent, and beautiful light source is natural sunlight. Most of our photography will be outdoors, so the use of sunlight is our obvious choice. The color of the sunlight varies according to time of day. Most out door color film is balanced to reproduce colors most accurately from two hours before until two hours after mid-day. Earlier or later times may cause the finished picture to be too red. Overcast or cloudy days will give a softer, more pastel rendition, but the slides may take on a bluish cast. These color shifts can be corrected by the use of filters. A good book on basic color photography can be a big help here. Back-light, with the sun shining through the petals is particularly effective. The trusses seem to glow with an incandescence of their own. If it is necessary to lighten a particularly dark shadow area, a reflector made of crumpled tinfoil, a piece of newspaper, or even a white shirt-front can be used to bounce a little sunlight into that dark corner. Really what I'm saying is, try to explore the full potential of natural sunlight before complicating your life with flash, strobe lights or whatever.
O.K., we now have our camera, lens extended with a bellows, loaded with fresh color film, bright sun and a rhody waiting to have its picture snapped , what now?
Of course you've read the instructions that came with your camera and bellows unit but how about that little piece of paper that came with the film. The people who made that film have a large stake in your ability to take satisfactory pictures so they have provided you with some very important information. if you follow their recommendations as to shutter speed, etc. you should be close to right on. To be sure, try bracketing your exposures; that is in addition to one shot at the recommended setting, take a shot l/2f stop above and one f stop below the recommended one. That way one is bound to be perfect. By keeping notes of your exposure times you will soon establish your own standard exposures for the majority of your work in the future.
One thing that must be remembered is that you must increase your exposure as you increase your lens extension to get closer to your subject. The exact amount of exposure increase will usually be found on a series of scales engraved directly upon the extension device. By the way, most filters will also require an adjustment of exposure as well. If, however, you are fortunate enough to have a camera which automatically adjusts exposure by reading the light coming directly through the taking lens, these problems are solved for you by virtue of the camera a electronics.
A word about automatic cameras is perhaps in order here. There are cameras available today which literally think for themselves. This is fine for most picture-taking situations but for those special instances which occasionally creep up, you want the option of overriding the electronics.
A couple of years ago a new camera came on the market which offered, I thought, great possibilities. The camera was the Polaroid SX-70. It had reflex viewing, automatic exposure, could focus to 10 1/2 inches without attachments, to 5 inches with a simple converter. True it did not produce slides which could be shown to large groups simultaneously but if your needs were to provide records for yourself or pictures to show to only a few people at a time this didn't seem to be a serious drawback. I bought one and immediately hauled it off to Philadelphia for the 1976 AR.S. Convention. The results were a disappointment. Although the camera performed flawlessly, the colors produced on film bore only distant resemblance to the flowers portrayed. The film does a great job on people, dogs and the like, but rhododendrons are not its strong suit. The moral of this story is, before going out to photograph a once-in-a-lifetime event, know your equipment thoroughly.
In conclusion, I hope that I have provided you with a little knowledge and a little nudge to capture your rhodys on film. Good Luck!
SPRING COMES TO THE SOUTH
BY JERRY DURAND
Reprinted with permission of Modern Maturity, February-March, 1976
Talk to any East Coast lover of beautiful flowers and he or she will surely mention the gardens of North Carolina, South Carolina and Virginia. Ask, "When is the best time to visit them?" and the answer will be "When the azaleas are in bloom."
Around Charleston, S.C. ,blooming time is about the third week in March. It's the second week of April in Wilmington, N. C., and the fourth week of April in Norfolk, Va.
By moving with spring as it slowly makes its way north, flower lovers can stretch the arrival of spring into a never-to-be-forgotten five weeks or more of seeing nature at its best. This is the time when myriad colored azaleas mingle with pink and white dogwood, not just in world famous gardens but wherever one looks.
The four gardens near Charleston are undoubtedly among the finest in the world:
1) Cypress Gardens are owned and operated by the city of Charleston. They are located in the 250-acre Dean Hall Plantation on the Cooper River, which was started as a garden in 1927 by Benjamin R. Kitteridge. The gardens were donated to the city in 1963 and can be explored by footpaths or boat. Their ink-black waters reflect the surroundings, mixing multicolored flowers, bewhiskered cypress trees, blue skies and white fluffy clouds into a masterful combination of colors that are beautiful beyond compare. Entrance fee is $2.50.
2) Magnolia Gardens on the Ashley River has been owned by the Drayton family for more than 280 years. The gardens were started by the Rev. Mr. Drayton in 1843. There are 25 acres of flowers and 16 acres of lawn. Visitors are amazed at the size of the azaleas, which are nevertheless dwarfed by giant veiled oaks. Mirror-like reflection pools, a snow-white bridge, ducks and geese all combine to make it a photographer's dream come true. Entrance fee is $.50.
3) Middleton Place Gardens and Stableyards are America's oldest landscaped gardens. They were started by Henry Middleton, President of the First Continental Congress, in 1741 and completed a decade later.
Azaleas are everywhere. There are 35,000 of them on the hillside bordering Rice Mill Pond. The patriarch of the plantation is the Middleton Oak which is said to be more than 900 years old. Middleton is open all year. Entrance fee is $2.50.
4) The 75-acre municipally owned Edisto Gardens of Orangeburgh, S.C. ,are located in town along the North Edisto River and the gardens are open all year. The old saying, 'The best things in life are free,' is certainly true here. Moss-draped trees form a canopy over azaleas so laden with blooms that one wonders what is holding them up. The brown-colored river snakes an ideal reflection pool for all this panorama of beauty.
Every spring Wilmington, N.C., celebrates the blooming of azaleas with a city-wide celebration that lasts an entire weekend. in and a-round the city are three beautiful gardens:
I) Orion Plantation Gardens is the oldest. The plantation, founded by 'King' Roger Moore in 1725, is situated on the west bank of the Cape Fear River. A footpath leads visitors through the formal gardens, past a lagoon where white swan swim, then on to the Colonial graveyard where 'King' Roger Moore' is buried. Then it doubles back, finally coming out on a beautiful azalea-studded lawn that surrounds an elegant Southern mansion. There is an entrance fee.
2) Airlee Gardens are located on Wrightsville Sound. The scenic drive is interspersed with walkways leading to places that can best be visited on foot. This includes majestic Airlee Oak, one of the oldest cemeteries in the country, and Old Lebanon Chapel. Needless to say there are azaleas everywhere. A fee is charged
3) The city-owned Greenfield Gardens in Wilmington has a five-mile drive around Greenfield Lake. There are also footpaths along part of the lake and a replica paddlewbeel steamer to tour the lake. The four-day Azalea Festival is entering its 26th year. Activities include a parade, garden tours, band concerts and the Azalea Queen's coronation.
If a carnival barker were to talk about the Botanical Gardens of Norfolk, Va., he might be tempted to start by saying, 'Don't go away folks, the best is yet to come.' The 175-acre gardens can boast of 225, 000 azaleas, miles of footpaths trackless trains, boats, and a personal garden for the blind where sightless visitors may touch and smell flowers -- there are Braille markers to identify the flower: and shrubs.
One of the most beautiful places in the gardens is Mirror Lake, the scene of the coronation of the international Azalea Queen. Luci and Lynda Johnson, Tricia Nixon and the daughters of the Prime Ministers of Belgium, Holland and Norway have served as Queen of the Festival.
There may be a better way to welcome spring than visiting the flower gardens of the East Coast. Somewhere there may even be a garden with prettier azaleas and dogwood. if there is, you'll have to find it.
NOTES FROM NANTUCKET
Elsewhere in this issue of the Rosebay is a reproduction of the Bronze Medal Citation presented to Louis A. Cook. It is especially pleasing to me to include the citation on these pages because of a very personal reason. It was Louis Cook who some years ago introduced me to the genus rhododendron and to the American Rhododendron Society. It was his contagious enthusiasm which began my own personal love affair with rhodys. To list here Louie's many contributions to the Massachusetts Chapter would be a restatement of what is already well known. Instead, please allow me to offer my warmest congratulations to a good friend.
After a few days respite, the thermometer here on Nantucket has again plummeted to below freezing. From all indications, this winter has to be one of the most severe in recent history. Our island has been pretty much cut off from the mainland as far as boat service is concerned. The ferry has been able to come with goods for the supermarkets only when a Coast Guard ice breaker has been able to break a channel through the ice. With the many problems the cold weather has produced for us this year, our attentions have been directed to areas removed from rhododendrons. When we were able to assess the damage during a recent warm spell you can imagine what we found. With a wind-chill factor almost constantly below zero and often -40 - 50 below, the destruction was virtually complete. The only apparent survivors were of the small-leaved varieties, such as 'P.J.M.', 'Ramapo', 'Purple Gem', and certain evergreen azaleas. Our only recourse is to begin anew in the spring. We hope those of you on the continent fared better.
This issue of the Rosebay will be the last of which r will serve as editor. Other demands on my schedule as well as the difficulties of being isolated on an island are major factors in this decision but not the most important. I have served as your editor for nearly seven years. It has been a most rewarding and fulfilling experience. The friendship of many fine people met through these pages represents a compensation far in excess of what one should expect for so modest an effort. But seven years is a long time for one person to reap the benefits of such an association. It is time to step aside so others may have the opportunities to serve you which I have enjoyed. I hope to be able to continue to be involved in some way with the publication of the Rosebay in the future but in the meantime, let me thank all of those in the past who have contributed much in time and effort to this publication. And to you dear reader, for your indulgence, a sincere thank you.
THE IDEAL DWARF SHRUB
BY PETER COX
Reprinted from The Garden
Journal of the Royal Horticultural Society, March, 1976
I am often amazed at the adaptability of the alpine rhododendrons from the windswept mountains and high plateau of the Himalayas and western China. These plants may be buried under snow for half the year and enveloped in driving mist for the other half. But in our conditions they thrive, with very few exceptions, provided a few basic cultural factors are noted.
In the past the attention was focused on the larger rhododendrons but now with the size of gardens shrinking, it is the small rhododendrons which are proving to be ideal dwarf shrubs. Their variety is astonishing. Every flower shade from lavender to blue, is found in the wild species. Likewise flower shape, leaf size, colour and texture, habit and flowering season show tremendous variations. Some years we have rhododendrons in flower in every month. Many dwarfs have aromatic foliage which adds further to their attraction.
This prodigious diversity of form (there are no less than thirty yellow flowered species usually under two metres in height) not only extends the scope for what can be planted in the way of species but gives exciting prospects for the raising of hybrids. The majority of dwarf species belong to the so-called lepidote or scaly rhododendrons and most of these are compatible with each other for hybridizing, but not with the other group, the elepidote or non-scaly species.
Not all these dwarf species come from the mountains of south-east Asia although the great majority do. Outliers come from Japan, Siberia, the Arctic Circle, the Alps of Europe and North America. From the most unlikely climate of the Gulf of Mexico, U.S.A., comes R. chapmanii. Although it is difficult to grow here it does show what varied districts and climates these species cover. There is, too, a great possibility of even more versatile hybrids being raised when these far-flung species are crossed.
Another way in which miniature rhododendrons differ is in the various soil conditions in which they are found growing wild. Most people know that rhododendrons are notorious haters of limestone and chalk and yet several species are found growing wild on limestone. In cultivation, it has been discovered that those species collected on limestone are in fact those most lime tolerant. While I doubt if it will ever be possible to grow even hybrids of these species in chalk, it should be well worth the effort for people on relatively alkaline soils to carry out their own breeding programme, relying mainly on these lime tolerant species. In this category are R. ciliatum, hippophaeoides and hirsutum in the scaly or lepidote group and R. didymum, scvphocalvx and williamsianum in the non-scaly or elepidote group.
I was bitten with the hybridizing bug over twenty years ago. I had just come to settle near Perth at Glendoik to start developing our rhododendron nursery. One day, I visited Ascreavie, the lovely garden of the late Major George Sherriff and of Mrs Sherriff who both spent many years collecting plants in Tibet and Bhutan. When walking around, I suddenly spied a tiny rhododendron not more than 3 inches (7 1/2 cm) high with extraordinary large deep saucer-shaped yellow flowers. This was R. ludlowii, named for the late Mr Frank Ludlow, Major Sherriff's collecting companion. This was and still is a rare and somewhat difficult plant but I was lucky enough to acquire one.
A quick study of the then current RHODODENDRON HANDBOOK ON HYBRIDS revealed that R. ludlowii had never been used as a parent. The next year, both ludlowii and the yellow Lapponicum, chryseum flowered and following instructions of previous hybridisers, I duly removed the corolla (petals) and stamens(to leave nothing to attract passing insects) of the proposed male parent, chrvseum and pollinated it with the pollen exuding from the stamens of ludlowii
Having labeled it and noted the cross in a book, I watched with delight as the ovaries swelled and duly collected the browning capsules in autumn. The seed germinated well and in two years the seedlings started to flower. Waiting for one's own hybrids to flower for the first time, having noted the fat buds forming the previous autumn, is to me one of the greatest anticipations of life. Over the years, the sheer joy or perhaps disappointment of watching new seedlings bloom, has never lessened.
Perhaps I had some hidden insight of what might make good parents hut I am inclined to think it was just beginner's luck. The hybrid, whose history is related above, was named 'Chikor' and received the Award of Merit at its first showing and was also given the Reginald Cory cup for the best man-made hybrid of the year. Later, it received the F.C.C. at the Wisley trials.
A great fault of novice hybridisers is to be haphazard and just make a cross because two plants happen conveniently to bloom at the same time. It is most important to have some goal in mind and ruthlessly discard everything that does not reach a high standard. Two questions must be asked when viewing one's own hybrids. First, is the plant a definite improvement on its parents and second, is it really distinct from previously raised hybrids? Do avoid the pitfall of looking at your own hybrids through rosy spectacles, and only name the best.
I must be realized that many more failures than successes are usual. Sometimes there is no seed, at other times the seedlings are all identical with the seed parent while often as not the seedlings are only worthy of the bonfire. There is no room here to go into further details of the art of hybridizing. More information can be had from my own book DWARF RHODODENDRONS or David Leach's RHODODENDRONS OF THE WORLD, now out of print.
Extraordinarily little hybridisation of dwarf rhododendrons has been done up to now. But there is one line of breeding that covers the so called blues, and most of the crosses have been accomplished by using the Lapponicums impeditum, fastigiatum, both blue-purple; russatum, deep blue-purple and intricatum pale lavender-blue, crossed with the much larger augustinii. There are many named hybrids in this group, several of which are capable of reaching 2m. (6 feet) or more. Amongst the best of the lower ones are 'Sapphire', light blue; 'Songbird', deep violet-blue, and the newer 'S. Merryn', deep purplish blue. These flower in April-May.
There were very few dwarf yellow hybrids before I started and most of these were either tender or straggly. 'Chikor' is compact and extremely free flowering, while the newer 'Curlew', this time ludlowii x fletcheranum has larger leaves and flowers. The latter are so prolific that hardly a leaf can be seen when in full bloom. We received the F.C.C. for this in 1969 and it is already very popular. Both usually flower in May.
Good pinks in the real dwarfs are rather elusive and many efforts to hybridise them have met with failure. Amongst the best clear pink species are certain forms of cephalanthum and especially cephalanthum var. crebreflorum which is a little beauty. This has aromatic leaves and narrow tubular flowers in clusters like a daphne. I did raise a hybrid of the latter but i was inferior to its parents so was discarded. The dwarf racemosum from seed of Forrest 19404 is very fine with clustered heads 4 small deep pink flowers. To me, there is no really good low dwarf pink hybrid for general planting and here is work for the hybridiser to do. My own efforts with the dwarf racemosum, using it as the seed parent, nearly always result in just racemosum seedlings. 'Pipit', a selection of mine from wild collected lowndesii (a very dwarf rare deciduous yellow) is obviously a hybrid with the related lepidotum. It is a very neat dwarf with flat delicate pink flowers Unfortunately it needs some protection from spring and autumn frosts. An un-named hybrid of sargentianum x kotschyi (the latter is found wild in eastern Europe) was raised in Edinburg and drew considerable attention last spring, both at the Rhododendron Show in London and in our nursery. 'Pink Drift', a good grower, is really magenta-pink. There are several semi-dwarfs of merit like the early 'Tessa Roza' and the hard to propagate racemosum hybrid 'Fittra'
Whites are not common among dwarf species and most are albino forms of coloured species as in our native white heather. The lovely white leucaspis is also of borderline hardiness but is proving a good parent for low white hybrids. Being early flowering, most of its progeny are also early. 'Ptarmigan' (microleucum (an albino Lapponicum) x leucaspis) is a pure white for which we received an F.C.C. in 1965. Ii grows quite rapidly but needs careful positioning to avoid the dangers of March-April frost. Several hybrids open pale pink and fade to white. A good and easy plant of this colour is 'Sarled', which opens in late May and is long lasting. This again has the daphne type flowers which I am very fond of. Rather similar but of a uniform creamy white is 'Maricee', an American hybrid of sargentianum which was much admired in our nursery this spring.
Dwarf lepidote red species are very scarce. There is cremastum 'Bodnant Red' A.M. with neat little red thimbles in June, some of campylogynum that are similar, and calostrotum 'Gigha' F.C.C., one of the finest dwarfs with masses of large rose-crimson flowers in April-May and nice glaucous foliage. I crossed the cremastum with this calostrotum and one seedling looks promising. The darkest forms of the European ferrugineum, the Alpine rose, and hirsutum also approach red in their flower colour.
The non-scaly species have few real dwarfs but the often shy flowering forrestil var. repens with waxy-scarlet flowers has given a whole range of fine red hybrids. Highly recommended are the dark red 'Carmen' and the excellent German trio 'Elisabeth Hobbie', 'Baden Baden' and 'Scarlet Wonder'. Work is now being done to produce low reds with the round full trusses usually found in the popular large hybrids.
There has been much publicity on yakushimanum and its progeny. Waterers have named a whole series of these. Some are good but there is still room for improvement and the same may be said for all dwarf hybrids.
Another little tried line is breeding for foliage. Various combinations of the glaucous leaved lepidostylum viridescens, calostrotum and fastigiatum should lead to fine foliage plants while the rare proteoldes, roxieanum and tsariense may give us beautiful dark leaves and lovely indumentum.
These low rhododendrons appreciate fairly sunny conditions to retain their habit and floriferousness, especially around the wet western seaboard. All enjoy plenty of organic matter well mixed into the soil. Peat beds are ideal. These can even be made raised above unsuitable clay or alkaline soil. A good plan is to place the lowest growers at the front, gradually increasing the height to the back of the bed. All prefer weed free soil but this is now easily accomplished with the careful use of modern weedkillers.
Massachusetts protects by law, the mayflower, cardinal flower, all species of wild orchids, and all wild azaleas.
(source: The Boston Globe, February 12,1976.)
BY DOROTHY SWIFT
My garden notebook initially consisted of budget records; having acquired the vice of collecting plants, I proceeded to document it carefully. Those of you who don't yet keep records might consider starting a notebook for your own benefit. It becomes hard to recall several years hence the exact severity of a winter and for the benefit of others- we're eventually going to want to pool information about various plants to evaluate them in our region.
I use a large spiral notebook so pages don't get lost. Odd papers can be pasted in. The entries I make are quite simple; authors in the ARS Quarterly Bulletin have given detailed lists to use if you want to evaluate new hybrids etc. I have several categories:
1. Lists of plants acquired each year inducing source, size, cost of each.
2. Location of plants. Simple sketches showing where new plants are situated relative to landmarks such as trees, rocks, older plantings.
3. Bloom record. A page is divided into columns to list date, flower color, year planted whether this is first bloom and, if so, size and cost when planted.
4. Climate. This includes mention of atypical seasons such as a cool late spring, dry summer etc., but winter severity is the important category I now use my own thermometer and record those nights when the temperature drops below 100F here. It's a good idea to note winter damage sustained by plants and to record other responses such as sensitivity to drainage or insects or slow growth from undergoing only one flush per season.
5. Material for future reference such as notes concerning plants seen at flower shows, on garden tours, or discussed at A.R.S. meetings. These may be helpful in plant acquisition or hybridizing. And you want to record your own activities such as crossed made, seeds germinated or new fertilizers tried.
I'm afraid our winter of 1975-76 has provided a lot of material for our garden notebooks. Be sure to write it down.
A VISIT WITH Mr.& Mrs.Juko Otsuki
Some five years ago I became interested, more than usual, in rhododendrons and azaleas. Every year we would go through a period in which we would try to determine what flowering bush would enhance our place, and would make several trips to a local nursery. Knowing that plants were expensive, I decided to see what would result by planting seeds from one of our own unknown floriferous rhododendrons. After I had gotten over how small seeds could be, I placed these in a crude arrangement under cool fluorescent lamps. I had managed to remember a few things mentioned in Krantz's GARDENING UNDER LIGHTS. A few survived. When these were an inch or so high I transferred them directly outside into our sandy garden to fend for themselves, perhaps prematurely, in retrospect. In spite of the fact they were left outside, these grew and through the years were helped along. (As the plants are loaded with buds this year, we expect quite a display this spring for the first time.
At about this time, I decided to find out more about propagation of azaleas and rhododendrons. I had heard about plant growth promoting compounds and decided to find out more about them from the Massachusetts Horticultural Society. I received a copy of an article describing such compounds put out by a Carolina biological supply house. This only whetted my appetite and it was not long afterwards that I became aware of David Leach's book RHODODENDRONS OF THE WORLD, Clement Bower's RHODODENDRONS AND AZALEAS and Judith Berrisford's RHODODENDRONS AND AZALEAS referenced in the encyclopedia Britannica. These sources got me started in earnest and shortly thereafter I saw somewhere a reference to a rhododendron society located in Oregon which turned out to be the ARS. ft was through them that I realized that there was a Massachusetts chapter.
Prior to this time the two years of starting seedlings and cuttings via a ramshackle propagating structure under inadequate lights convinced me that drastic improvements were necessary. I thereupon constructed a two tiered 4'x8' structure fitted with fluorescent light fixtures, controlled by a time switch. The following winter, I started 40 cuttings, mostly rhododendrons. Most of these took. This experiment taught me the importance of light, temperature and moisture in plant propagation. The following year a method was devised to provide high humidity simply by enclosing the growing area with polyethylene sheeting. Quite a few cuttings were 'stuck' in a 50/50 mixture of sand and peat. Most of these were the usual types:'Nova Zembla', 'P.J.M'., 'P.den0uden', 'Lee's Dark Purple', 'Dora Amateis', 'Windbeam', 'Purple Gem', 'Scintillation', carolinianum and 'Chionoides'. All responded remarkably well. 'Chionoides', carolinianum and 'Windbeam' seemed a little slower taking. Along with these rhododendrons I had planted quite a number of evergreen azaleas which took root almost 100 per cent. Needless to say, I was overwhelmed with the way that the cuttings responded. In looking back, despite the size of the propagating structure the experiment was a success.
During the last couple of years I have been enlarging my background with respect to propagation, )particularly with the amount of illumination required and the new growing fluorescent lamps, such as the Sylvania Wide Spectrum type. Much of my propagation efforts have been based on the ordinary rhododendrons mentioned above. Thanks to the ARS cutting exchange, I have been able to propagate 'Boule de Neige', smirnowii, 'Hon. Jean de Montague', 'Mrs. W.R. Coe', 'Blue Peter', 'Blue Ensign' and 'Princess Margaret' quite satisfactorily It will be interesting to see how 'Dexter's Pink', 'Spring Parade', 'Betty Hume', 'Elie', 'Janet Blair', 'Gable's Redhead' and 'Dexter's Horizon', all from this year's cutting exchange, will perform. This year I have been blessed with an abundance of cuttings from a number of friends to whom I am indebted. Although much of my efforts have been directed to rhododendrons and azaleas, I might mention that hollies, such as Ilex burfordi and 'Nellie R . Stevens' have also done very well.
For a simple yet durable label for your rhododendrons, use Dymo labeling tape. After embossing the name of the plant and any other pertinent information, roll out enough excess to fully surround the stalk, leaving plenty of room for future growth plus about two inches. staple the ends together with an ordinary stapler after wrapping the tape around the stalk. DO NOT remove the white backing from the tape as this makes the label more durable. We have some labels which have survived for five years with only an occasional re-stapling required.