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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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Standardizing Descriptions Within The Genus Rhododendron
Reid M. Denis, Great Falls, Va.

        In a decade which has the know-how to send rockets to Mars, the botanic world is still largely shaped by thought patterns going back to the 16th and 17th centuries. While the man-in-space program coils for a spring at the moon. the best horticultural brains continue the classic ordering of plants in an abstruse, unwieldy fashion. It is the author's contention that this gap can, and must, be bridged and that modern technology now provides the means to make a radical breakthrough in the systematic description of plants. Such non-taxonomic attributes as plant appearance, time of bloom, growth characteristics, hardiness, and many others may be subjected to observation on a mass scale, and to ordering by non-scientists in a scientific manner, to produce a body of material of equal value to scientist and non-scientist alike. The burden of this paper is to suggest a system of standard descriptions which can be applied to the genus Rhododendron, and which should prove of very real value for the landscape gardener as well as the plant breeder in the years to come.
        The present system of identifying the species of the rhododendron family has its origin in classical botany. It is essentially based on microscopic study of a limited number of features distinguishing one group of plants from another. It is a system which has been refined over the centuries by a small group of scientifically trained students who understand and, therefore, are able to use it. Most of us are not trained botanists and cannot use the ordering scheme to any practical effect.
        Reference to published materials on rhododendrons and azaleas give the interested reader descriptions which are of little or no value in distinguishing one plant from another. Poetic rather than precise terms are used to describe colors and the descriptive phrases applied to leaf and growth characteristics not only lack poetry, but precision as well. There are few exceptions.

Concise Terms Valuable
        The Quarterly Bulletin of the American Rhododendron Society has recently published some descriptions of new rhododendron clones in precise terms.
        In most instances these are introductions of David Leach. It is gratifying to see a rhododendron breeder and student of his stature applying to the description of his progeny the same scientific precision he uses so generally in his authoritative book. It is to be hoped that his example will be widely followed by other breeders.
        B. Y. Morrison is not only a famous hybridist but is the first plant breeder in the rhododendron world to have systematically described the plants that he produced. He did so using the Ridgeway color charts to describe flower color, and formulated a set of reasonably clear and regularly defined general phrases to cover unusual leaf or growth characteristics. However, valuable as this description effort was and is, it is of only limited use in the identification of particular plants. Apart from Morrison's and Leach's efforts, there have been very few attempts to describe systematically the characteristics that are of interest to the non-scientist.
        Few of us are walking reference libraries or human computers, like Drs. Skinner and Bowers. Few can tell at a glance, with absolutely surety, the name of any particular plant. But there are gross, general descriptive characteristics to be observed which are useful and valid in distinguishing differences among the multitude of clones in the rhododendron world, which are not commonly used today. Were we to observe systematically and report substantially on them to a central point, these descriptions could be collected, collated, published and made available in a form that would be invaluable to any intelligent enthusiast in this field.
        Close study of the various books on rhododendrons reveals that there are certain non-taxonomic attributes which help to distinguish one plant from another. The author's first step was a listing of terms most frequently used. A preliminary draft was formulated as a guide for a limited number of observations on azaleas. This list was modified and expanded, a check sheet devised, and the data in Morrison's Pamphlet converted (coded) according to the scheme presented herewith, key-punched, and printed in the standard format shown on the accompanying printout. A study of the alphabetic listing clearly reveals peculiarities of leaf and growth characteristics of real value in distinguishing one clone from another. (This first list of distinguishable characteristics, and the breakdown used within any particular characteristic, can of course be modified as further observations are obtained.)
        Color Descriptions Somewhat Difficult To begin, one of the most serious stumbling blocks in identification is associated with color description. Few of us will translate the phrase "clear pink" in the same way, and none of us will feel that any of the available color swatches exactly matches the ethereal beauty of a particular flower in bloom. This applies to Ridgeway's Chart as well as to the Royal Horticultural Systems Chart and to the Nickerson Color Fan printed by the Munsell Co. Of these three standardizations of color description, only the Nickerson Fan is generally available, relatively inexpensive, and it alone is fully standardized by colorimetric methods. It offers the advantage that its descriptive phrases are related to letters and numbers which follow a logical succession, and are readily understandable. It is unique in that these color designations can be directly expressed on punch cards and manipulated by standard business machines or by computer equipment. The colors are unvarying and it would matter not whether an observer were American, English, German or Japanese. Anyone could use this fan to report color descriptions in a language understandable to all. Unfortunately, because of the small demand, its price of $7.50 unduly limits a wide use by amateur gardeners attempting to describe colors.
        The descriptions of the flower forms and of the truss types are particularly unsatisfactory. In the Bowers and Leach books, there are extensive sketches of numerous forms of rhododendron flowers. To those who have either book and are willing to make an extra effort, some relationship can be found between the flower form under observation and a corresponding sketch. If reported on, using the lettering systems found in these texts, the resultant data could be mechanically manipulated. (It would be highly desirable if the Rhododendron Society would sponsor simplified drawings of the more clearly distinguishable basic flower forms and make them available to reporters who contribute to the development of a standard descriptive system.)
        In the aforementioned books, the leaf characteristics are adequately described. There are, even among the more grossly varied rhododendron leaves, clearly distinguishing types of tips and bases, general shapes, sizes and variations of hairiness or glossiness observable among individual clones. The set of characteristics used by the author is based entirely on Leach's hook which has an excellent plate describing the basic shapes of rhododendron leaves. The writer would be happy to make available to anyone who would contribute data to this project, Xerox copies of Leach's sketches for use in making observations. Further refinements in describing the growth characteristics of this family undoubtedly will emerge, but the ones suggested here at least provide a point of departure.

Varieties Too Numerous To Keep In Mind.
        With the rapid proliferation of rhododendron clones (as plants especially suited for particular purposes are developed), the number is becoming so enormous that it is now beyond the range of comprehension for even the most knowledgeable of specialists. For this reason, the author feels that some standard descriptive system should he undertaken, and soon. Once agreed upon, and with the collection of data begun, a body of information would emerge that could be manipulated for numerous purposes. Take an obvious example. Landscape architects or gardening fans never know more than a few alternative replies to the question, "What grows to such and such a height, blooms at such and such a period, and is generally in such and such a range of colors for use in garden planting?" This is a query which can be answered in a matter of minutes with a business card sorter. (An illustration of such a query and the printout is attached.) The reply to a question as general as "What mid-season pink azalea should be planted in front of a tall, mid-season white azalea?" is simple and straightforward. The resulting list is limited enough that the landscape planner has only to check with a nurseryman for available selections. The reply to a more sophisticated query concerning planning a succession of blooms of a particular color or a series of colors, would also be well within reason. Choices would be presented clearly, instead of the bewildering array of alphabetically ordered names and vaguely described colors such as is presently available.
        Another useful purpose that could be served by this system is that of assisting in plant identification. Mechanically narrowing the field could enormously simplify the problem. Occasionally an exact match between "Plant X" and a previously described plant would occur. More frequently the result would he a small list of alternatives - not unequivocal, but helpful nonetheless.
        Furthermore, such a descriptive system could he of immense value to breeders. Its use would allow for a quick determination of whether or not a new clone has characteristics of color, leaf, growth, hardiness, or time of bloom sufficiently different from available ones to make it worth the effort to propagate and introduce.
        This system could be further extended to the advantage of the plant breeder. Card-punched data from the international stud hook would list the parents of each identified clone as now given. From this data-base, the results from a particular parent, or set of parents, easily could be determined, and a complete list of progeny obtained almost instantly. Thus a knowledgeable breeder surveying this list could get a very clear picture of previous breeding efforts with any particular parent or set of parents.
        One other point is worth mention. Should Americans begin to collect data and publish the results of a standardized descriptive effort, said effort inevitably would be a vanguard for international reporting on the same family. The color standard is already internationally accepted, and the other characteristics could also readily be translated and reported upon in exactly the same fashion. Punched cards can he exchanged, and reports from observer; in Europe or Asia would tremendously widen knowledge of the hardiness and suitable ranges of particular clones available elsewhere in the world. Once it is demonstrated that an international standardized descriptive system can he used with this genus, its application to other families in the plant world is sure to follow.

Business Machine Methods
        Those not familiar with business machine equipment may not appreciate how readily data ordered in a standard format can be manipulated. For those interested, it is suggested that they consult any standard reference work on the basic techniques, but for others, a two-paragraph explanation may suffice to give an understanding of what is involved. The standard IBM card is divided into 80 columns. One column only is required to print in language readable to a machine, an identifying letter or number. With data relating to any factor always recorded in the same one or group of columns, it becomes possible, mechanically, to sort for this element of data. For example, if hardiness ratings were described in the standard numerical ratings system from 1 to 5 in Column I of the card, the machine could list all plants of any specified hardiness rating. It is simple to sort sequentially in one column at a time, narrowing the remaining cards on each successive sort to an ever smaller number. Thus, after sorting for hardiness ratings, one could sort for time of bloom. A third sort might select a list of plants with a particular growth characteristic; a fourth, those of any desired color (since this, too, can he expressed in machine language, thanks to the Munsell system). The landscape gardener asking for a Zone three, mid-season, five-feet tall, white rhododendron would receive a small number of cards, listing the clonal names meeting his criteria - the result of the various selection steps.

        Equipment to manipulate these cards is widely available in industry. universities and government. It can be rented at low cost and copies of the cards can he made inexpensively for general distribution to regional centers in this and other countries should this seem desirable. The main problem to be faced is not that of manipulating the data, it is of acquiring the data to be manipulated.

        It is hoped that the Society would sponsor printing the guide for a standardized descriptive system in pamphlet form to be used for general reporting. Experience indicates that an observer quickly develops the ability to record plant characteristics in about five minutes per plant. A team of two - one to observe and one to codify and record makes the job go much faster. If an observer notes a particular characteristic not fitting the classification scheme presented here, it should he reported in the Remarks Block. By using a common identifying number, different observations of, or special remarks concerning a particular clone, could be recorded without repeating the name, by merely providing the number. Data must he processed centrally so that an arbitrary identifying number can be assigned to the clone under consideration for use in consolidating all future observations. The numbers assigned to the Glenn Dale Group were assigned by B. Y. Morrison. There is no question that this scheme is technically feasible. It would, however, require the contributions of many individual observers, working to produce the data-base essential to the desired results. Should the Society wish to undertake this effort in describing plants of genus Rhododendron, the author would be happy to serve as secretary until a more formal organization could be established. Observations should be directed to him, to the American Rhododendron Society, or to the National Arboretum. He would also correspond gladly with any wishing to make suggestions or desiring to obtain mimeograph copies of the reporting guide and sheet. With contributions from the many interested friends of genus Rhododendron, a new and highly useful descriptive system could be developed, and a major leap forward achieved in the solution of the vexing problem of description.

Appended to demonstrate the validity and usefulness of the concepts advanced are:
a) a list of characteristics to be reported on
b) a standard reporting sheet
c) a sample page of the alphabetical printout of the Glenn Dale list
d) a "sort" for whites, arranged alphabetically, by season of bloom
e) a "sort" for a color based on the Nickerson fan.


1. Date of Observation: Give date of observation of the bloom, by day, month and the year in numerals. As an example, 6 May would be reported as 06054 and 20 April would be reported 20044.
2. Hardiness: Use standard hardiness zone figures, range from 1 through 9.
3. Group Name: Identify common group names. if known to you, such as Glenn Dale, Satsuki, Pericat, etc.
4. Clone Name: Give the accepted clone name of the plant, and any synonyms known should be given in the remarks column.
5. Number: If known.
6. Flower Characteristics:
    a. Report time of bloom in terms of:
          (1) Early 
          (2) Early Mid-Season
          (3) Mid-Season
          (4) Late Mid-Season
          (5) Late 
          (6) Very Late 
          (7) Other

  Code # Generalization of Season Time of Bloom (Wash., D.C.)
  1 Early  March or early April
  2 Early Mid Season Mid April
  3 Mid Season Late April
  4 Late Mid Season Mid May
  5 Late Early June
  6 Very Late Late June
  7 Other (specify)  

    b. Petal Color: Report petal colors in terms of the Munsell notation preferably, or...the Horticultural Colour
        Chart, or Ridgeway's Color Nomenclature.
    c. Blotch Color: Blotch color, if significant, using the color chart nomenclature.
    d. Size: Size of bloom as:
        (1) Under "
        (2) to 1"
        (3) 1 to 1"
        (4) 1 to 2"
        (5) 2 to 3"
        (6) Over 3"
    e. Type: Identify flower type by:
        (1) Single
        (2) Semi-double
        (3) Double
    f. Hose-in-hose: Check hose-in-hose column if appropriate.
    g. Special Characteristics: Identify any outstanding characteristics of blooms (by number). If more than one
        applies, indicate others applicable in remarks column.


Typical are:
  (1) Ruffled (5) Striped
  (2) Frilled (6) Sanded
  (3) Spider petals (7) Flaked
  (4) Spots (8) Flushed

    h. Flower form: The drawings of flower shapes given in Bower's book can be used to describe the flower forms. These should be reported by identifying number, 1-76.
    i. Number of Flowers in Truss:

     Give number of flowers in truss as:
  (1) Single
  (2) Two to three
  (3) Four to seven
  (4) Eight to fifteen
  (5) Over fifteen

    j. Truss Type: Identify truss type by use of descriptive numbers given in Leach's book, running one through
       eighteen; or use the letter characterizations given in Bower's book (a) through (zz).
    k. Fragrance: Check if fragrant.
7. Leaf Characteristics:

      a. Type:
  (1) Deciduous
  (2) Semi-evergreen
  (3) Evergreen
b. General Shape:
(1) Linear (6) Orbicular
(2) Lanceolate (7) Spatulate
(3) Oblong (8) Oblanceolate
(4) Elliptical (9) Ovate
(5) Oval (10) Obovate
  c. Base Shape: d. Tip Shape:
      (1) Obtuse (4) Cordate (1) Acuminate (5) Mucronate
  (2) Acute (5) Auriculate (2) Acute (6) Truncate
  (3) Cuneate (6) Rounded (3) Obtuse (7) Emarginate
      (4) Cuspidate  
  e. Color: f. Size:
  (1) Dark green (4) Glossy (1) Less than " (4) 2" -4"
  (2) Medium green (5) Hairy (2) " to 1" (5) 4" - 6"
  (3) Light green   (3) 1 - 2" (6) Over 6"

8. Growth Characteristics: Estimate plant at maturity.

   a. height:  

b. Mass:

      (1) Dwarf-under one foot (4) Tall-five to fifteen feet (l) Twiggy
  (2) Low-under three feet (5) Over fifteen feet (2) Open
  (3) Medium-three to five feet   (3) Loose

        The reporter's hardiness zone should be stated, together with his name and address, including Zip Code. If possible, a carbon copy of each sheet would facilitate the manipulation of the data assembled.
NOTE: Additional characteristics, such as presence or absence of scales, or type of scales, will be considered and used where desirable.

Plant characteristics

Sample Page from Alphabetic Print Out of Glenn Dale Azaleas
163985 Bagdad 4 5 RP8 /8 5 RP45/14 5   3 3 1 3 3   -
160043 Ballet Girl 3 5 R 55/10 5 RP38/7 4   2   2   4 2 -
  General Effect Orange Red
141808 Barchester 3 N 95/   4 9 2   1 2 3   -
  Small Green Dots Deep In Throat On Upper Petals
163778 Baroque 4 N 95/   5 5 2   1   3   -
  Stripes Sanded With 10P 5111
160085 Beacon 2 6 R 6 /12   3 9 2 1 1   3   -
  Does Not Sunburn, Garden Effect Nearly Scarlet
141801 Berceuse 3 5 RP66/ 12   4 9 2 1 2   3 1 -
182866 Betiina 2 5 8 34/12   3   3   2 2 3   -
  Carmine Effect
160120 Bishop 2 5 RP55/14 5 RP45/14 3 9 3   1 3 4   -
160120B Bishop 3 5 RP55/14 5 RP45/14 3 9 3   1 3 4    
  Underlying Tone of Yellow Enlivens Color, Anthers Dark
163784 Blizzard 4 N 95/   5 5 2   1   3   -
  Fine White, Chartreuse Throat, Few Stripes
160114 Blushing Maid 3 5 RP66/11   4 1 3   2   4   -
  Margins Sinuate
163796 Bohemian 4 5 RP55/14   4   2   1   3    
163847 Boldface 4 10P 5 /11 I0RP4 /12 5 2 2   2   3   -
  White Center
163928 Bolivar 4 5 RP66/12 5 RP45/14 5 9 2   1   3    
  Petals Broad-lobed, Blotch of Small Dots
163807 Bonanza 4 5 RP45/ 14 1 P 6 /12 4   2   1   3   -
160009 Bopeep 1 N 95/ 5 RP66/12 4   9 2   2   4   -


Print Out of White, Late Mid-Season, Glenn Dales
163879 Acrobat 4 N 95/   4 6 2 3 1   3 1  
163785 Allegory 4 N 951 75GY9 /4 5 5 2 3 1   3   -
163824 Altair 4 N 95/   5 4 2 3 1   3   -
163960 Angela Place 4 N 95/   5 9 2   4   3 3 -
163766 Antique 4 N 95/   5 5 2   1   3   -
163810 Artie 4 N 95/   5 9 2   1   2   -
163771 Ave Maria 4 N 95/ 75Y 9 /8 5 6 2   1   3   -
163869 Aviator 4 N 95/ 75GY9 /4 5 5 3   4   3 1 -
163778 Baroque 4 N 95/ 55 2 5 2   1   3   -
163784 Blizzard 4 N 95/ 5 5 2 5 2   1   3   -
163908 Bravura 4 N 95/ 5 9 2 9 2   1 2 3 2 -
163884 Cadenza 4 N 95/   4 7 2   2   3   -
163798 Carrara 4 N 95/ 75Y 9 /8 5 9 2   1   2 1 -
163791 Cavatina 4 N 95/   5 2   2   3   -
163825 Chameleon 4 N 95/ 5 GY8 /10 5 5 2   1   3   -
163862 Chum 4 N 95/ 1 GY82/9 4  5 3   4   3 1 -
163855 Cinnabar 4 N 95/   5 5 3   4   3 1 -
163839 Cocktail 4 N 95/   4  5 2   4   3 1 -
163987 Conquest 4 N 95/   5 5 2   3 2 2   -
163772 Consolation 4 N 95/   5 5 2   1   3   -
NOTE: 'Baroque to alphabetical list shows differences


Appendix E
Sample Page, Glenn Dale azaleas arranged according to hues, as given on Nickerson fan; then by values (lightest have highest numbers); and by chroma (lightest have highest); then by time of bloom; and finally alphabetically. Last column (dash) in dictates existence of remarks card containing supplementary data.
160129 Stampede 4 6 R 6 /12 RP38/7 4 4 2       1 2 3    
160080 Swashbuckler 4 6R6 6 /12 5 8 4 115 4 9 2   1   1   4   -
163984 Wildfire 4 6 R 6 /12 5 RP45/14 4 1 2       1 2 2   -
163906 Aztec 5 6 R 6 /12 75RP48/14 5   2       2   2 2 -
182874 Phoebe 3 6 R 65/85 5 RP8 /8 5 8 2   1   4   3   -
141901 Greeting 3 75R 7 /9   4 1 2       1   3    
160013 Emblem 3 75R 5 /12 75RP48/14 4   2       1   4   -
163097 Carnival 3 5 YR75/6 25R 4 /10 6 9 2 3     2   3   -
141903 Buccaneer 2 5 Y R65/12   4 9 2       2   3   -
141773 Juneglow 5 5 YR66/12   3   3 2         3   -
163932 Snowscape 5 75GY9 /4   4   3   1 2 1   4   -
160133 Rising Sun 2 1 P 7 /12   5   2       2   4    
163929 Sprite 2 1 P 7 /10 5 RP54/ 12 5 6 2       5   3   -
141805 Andros 4 1 P 7 /10   4   3 3       3 4    
201896 Luna 4 1 P 7 /10   5   2       1   3   -
163886 Welcome 4 1 P 7 /10 5 RP45/ 14 5 9 2       2   3   -
160130 Templar 2 1 P 6 /12 1 P 45/14 5 9 2 2 1     4 4   -
160128 Viking 2 1 P 6 /12 1 P 45/14 5   2 2         3 2 -
160079 Violetta 2 1 P 6 /12 1 P 45/14 4   2       1   3    
160083 Litany 3 1 P 6 /12 85RP32/10 5   2   1   1 4 3 1 -

Volume 19, Number 2
April 1965

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