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Journal American Rhododendron Society

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


Volume 15, Number 4
October 1961

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Summary of Replies to Questionnaire on the Best Rhododendrons, Azaleas and Methods of Cultivating Them in the Region Served by the Great Lakes Chapter
David G. Leach

        EXPLANATORY NOTE: In attempting to tabulate the replies to the questionnaires which were distributed a few months ago it soon became apparent that the climate extremes within our region made it imperative to classify the information according to the climate from which it came. Accordingly, the completed questionnaires were divided into two groups: those represented by zone 5b on the new plant hardiness zone map of the U. S. Department of Agriculture, and those which came from zone 6b of the new map, which is much more accurate than the old.
        Zone 5, then, as it is used below, is the "inland" region, 10 miles or more away from the Great Lakes, in New York, Pennsylvania (excluding Allegheny and Cambria counties), Ohio and southern Ontario. In Michigan it refers to the inland communities south of Port Huron but also to the lake shore area north of Port Huron.
        Zone 6 includes the regions within 10 miles of any of the Great Lakes (except north of Port Huron in Michigan) plus Allegheny and Cambria counties in Pennsylvania.
        The reports seem to come clearly from one zone or the other, and the arbitrary selection of a 10-mile limit from any of the Great Lakes appears to apply quite well for this purpose.
        This information should be of great value to our members and all are urged to preserve this report as a guide in purchasing Rhododendrons and Azaleas and in their cultivation of these plants. I have taken an editor's privilege of inserting comments in cases where the tabulation of the data alone does not reveal all of the useful information derived from it. Such comments are clearly identified in each case.
        The response to the questionnaire was gratifyingly large and reflected the cooperation and enthusiasm of our members which we have come to regard as a permanent characteristic of the Great Lakes Chapter.

RHODODENDRONS GROWN
   Average Bud Hardiness Average
(mathematical)
% of sun
best results

HYBRIDS

Ratings Zone 5 Zone 6 Zone 5 Zone 6
'A. Bedford' (lavender-blue) H-3 xxx    Good   65%
'America' (red) H-1 x Good Good 60% 75%
'Arthur J. Ivens' (rose) H-2 xxx   Good   75%
'Beaufort' (white)     Good   50%
'Belle Heller' (white)     Fair   75%
'Besse Howells' (purplish rose)     Good   75%
'Blue Peter' (lavender-blue) H-2 xxx Fair to Good Fair to Good 45% 55%
'Blue Tit' (blue) H-3 xxx   Good   70%
'Boule de Neige' (white, early) H-1 x Good Good 55% 80%
'Britannia' (scarlet) H-3 xxxx Poor Fair to Good 50% 65%
'Caractacus' (purplish red) H-1 x Good   55% 75%
'Caroline' (pale lavender)   Good Good 45% 60%
'Catalode' (white)   Fair   75%  
'Catawbiense Album' (white) H-1x Good Good 75% 90%
'Catawbiense Boursault' (lilac)   Good Good 80% 75%
'Catawbiense Grandiflorum' (lilac) H-2 x Good Good 80% 80%
'Charles Bagley' (red) H-2 x Fair     50%
'Charles Dickens' (red) H-1 x Good   50%  
'Chesapeake' (white)     Good   75%
'Conemaugh' (pink, early) H-2 xx   Good   65%
'Conewago Improved' (pink, early) H-2 xx Good   60%  
'C. W. Sargent' (red)   Fair   70%  
'Cunningham's White' (white) H-2 x Poor Good 75% 80%
'Dr. H. C. Dresselhuys' (red) H-2 o Fair Good 60% 85%
'Dr. H. J. Lovink' (red) H-2 o   Good   80%
'Dr. V. H. Rutgers' (red) H-2 x Poor Good 50% 85%
'Edward S. Rand' (red) H-2 o Poor Fair 50% 65%
'English Roseum' (purplish rose)   Good Good 75% 80%
'Everestianum' (lilac) H-2 x Good Good 75% 80%
'Fanfare' (scarlet)   Good   75%  
'Goldsworth Yellow' (apricot-yellow) H-2 xx Poor Good 50% 70%
'Gomer Waterer' (blush) H-2 xx Fair Fair to Good 40% 80%
'Ignatius Sargent' (rose) H-1 x Good Fair 65% 75%
'John Walter' (crimson) H-2 x Poor Good 40% 65%
'Kluis Triumph' (dark red)     Good   80%
'Lady Eleanor Cathcart' (pink) H-2 xx   Poor   50%
'Lady Primrose' (pale yellow) H-3 xxx   Poor   50%
'Lee's Dark Purple' (purple) H-2 x Fair Good 50% 80%
'Madame Carvalho' (white) H-2 o   Good   85%
Madame Masson' (white) H-2 x   Good   85%
'Mars' (deep red) H-2 xxxx Poor Fair to Good 40% 60%
'Maximum Roseum' (pinkish lilac)   Good   85%  
'Michael Waterer' (dark red) H-2 x   Good   65%
'Moser's Maroon' (red-maroon) H-3 x   Good   65 %
'Mrs. C. S. Sargent' (rose) H-1 x Good Good 75% 85 %
'Mrs. P. D. Williams' (white) H-2 xxx   Good   80%
'Nova Zembla' (red)   Good Good 50% 75%
'Parsons Gloriosum' (pinkish lilac)   Good   80%  
'Parsons Grandiflorum' (purplish rose) H-1o Good   80%  
'Pink Cameo' (pink)     Good   75%
'Pinnacle' (pink)     Good   75%
'Pioneer' (rose, early)   Fair to Good Fair to Good 50% 75%
'Praecox' (rosy lilac, early) H-3 xx   Good   80%
'Princess Elizabeth' (crimson) H-2 xx Poor to Fair Good 55% 80%
'Professor F. Bettex' (red) H-2 x   Good   85 %
'Purple Splendour' (dark purple) H-2 xxxx Poor Poor to Fair 45% 60 %
'Ramapo' (lavender-blue, dwarf)   Good Good 75% 75%
'Roseum Elegans' (rosy lilac) H-1 x Good Good 80% 80%
'Roseum Superbum' (purplish rose) H-2 o Good   80%  
'Satin' (pink)     Good   75%
'Sefton' (reddish purple)       75%  
'Souvenir de Dr. S. Endtz' (rose-pink) H-3 x   Good   65%
'Sappho' (white) H-2 xx   Fair   50%
The General' (red)     Good   75%
'Van Weerden Poelman' (red)   Good Fair to Good 75% 60%
'Vernus' (pink, early)   Fair   75%  
'Vulcan' (red) H-3 xx   Fair   50%
'Wilsoni' (Laetevirens) (lavender-pink)     Good   50%
'Windbeam' (white)   Good   75%  
Westcroft hybrid #1019     Good   80%

 

RHODODENDRONS GROWN
  Average Bud Hardiness Average
(mathematical)
% of sun
best results
SPECIES Ratings Zone 5 Zone 6 Zone 5 Zone 6
brachycarpum (white, late) H-2 x Good Good 75% 80%
carolinianum ("Punctatum"), (pink, early) H-2 xx Good Good 80% 90%
catawbiense (lavender) H-1 x Good Good 80% 80%
'Catalgla' (superior form of catawbiense var. album) (white)   Good Good 80% 80%
caucasicum (ivory) H-3 x   Poor   75%
discolor (white or pink, late) H-3 xxx Poor Fair to Good 40% 50%
fortunei (blush, early) H-2 xxx Fair Good 40% 50%
hippophaeoides (violet-blue, dwarf) H-3 xxx Good   75%  
impeditum (violet-blue, dwarf) H-2 xxx   Good   65%
keiskei (yellow) H-2 xxx   Poor   65%
makinoi (pink) H-3 xx   Poor to Fair   75%
maximum (white or pink) H-1 x Good Good 40% 65%
micranthum (white) H-1 x Good Good 70% 75%
minus (pink, late) H-2 x Good Good 80% 80%
mucronulatum (lavender pink, very early) H-2 xx Good Good 90% 90%
racemosum (pink, dwarf) H-2 xxxx Poor Fair 50% 70%
russatum (blue, dwarf) H-2 xxx Poor to Fair   65%  
smirnowii (lavender) H-2 x Fair to Good Fair to Good 75% 80%
wardii (yellow) H-4 xxxx   Poor   75%

The ratings following the color descriptions of both hybrids and species are those of the American Rhododendron Society as published in Rhododendrons 1956 as follows:

HARDINESS RATINGS MERIT RATINGS
H-l:  Hardy to -25 o - Not worthy of quality commendation
H-2: Hardy to -15 x - Low quality
H-3: Hardy to -5 xx - Medium quality
  xxx - Good quality
  xxxx - Highest quality

Those not rated were too new or were not grown widely enough to evaluate in 1956 when the ratings were last published.

EDITOR'S NOTE: The designation of bud hardiness as poor, fair or good is on the basis of the average. For example, if nine growers rated a clone "good" and one rated it "fair," the majority evaluation appears. If there was a sizable minority opinion, it is represented, with the majority, in "fair to good."

It is apparent from the replies that growers in Michigan prefer less sun than those elsewhere; one remarked that he would eliminate winter sunlight entirely. It is equally apparent that zone 6 growers elsewhere who are in a climate strongly influenced by the Great Lakes, prefer a good deal more exposure for their rhododendrons, probably because higher atmospheric humidity and a lower general light level makes this possible.

AZALEAS GROWN
  Average Bud Hardiness Average
(mathematical)
% of sun
best results
Deciduous Hhybrids Zone 5 Zone 6 Zone 5 Zone 6
'Aida' (Rustica, rose)   Good   80%
'Balzac' (Exbury, red) Good   75%  
'Basilisk' (Exbury, cream) Good   100%  
'Berryrose' (Exbury, pink) Good   75%  
'Bouquet de Fiore' (Ghent, salmon) Good   85 %  
'Bright Forecast' (Exbury, salmon) Poor Good 75% 85%
'Cecile' (Exbury, salmon)   Good   75%
'Coccinea Speciosa' (Ghent, orange-red) Good Good 100% 90%
'Daviesii' (Ghent, white) Good Good 90% 90%
'Devon' (Exbury seedling group)   Good   80%
'Directeur Moerlands' (Mollis, yellow) Good Good 100% 90%
'Dr. M. Oosthoek' (Mollis, red) Good Good 100% 85%
'Essex' (Exbury seedling group)   Good   80%
'Fire Ball' (Exbury, red)   Good   75%
'Freya' (Rustica, salmon, double)   Good   100%
'George Reynolds' (Knap Hill, vellow) Good Good 70% 75%
'Gibraltar' (Exbury, orange)   Good   75%
'Hampshire' (Exbury seedling group)   Good   80%
'Honeysuckle' (Exbury, pale pink) Good   75%  
'Hotspur Red' (Exbury, red) Good   75%  
'Hugo Hardyzer' (Mollis, red)   Good   100%
Ilam hybrids Good   75%  
'J. Jennings' (Exbury, crimson) Good   100%  
'Klondyke' (Exbury, buff-orange) Good   65%  
'Koningen Emma' ('Queen Emma')        
(Mollis, orange) Good Good 100% 100%
'Lemonora' (Mollis, yellow) Good   100%  

Mollis hybrids (reported short lived)

Good Good 80% 85%
'Nancy Buchanan' (Exbury, white)   Good   75%
'Nancy Waterer' (Ghent, yellow) Good Good 85% 90'/0
'Narcissiflora' (Ghent, double yellow) Good Good 80% 90%
'Norma' (Rustica, salmon, double)   Good   100%
'Oxford' (Exbury seedling group)   Good   80%
'Persil' (Knap Hill, white) Good   75%  
'Pucella' (syn: 'Fanny')        
(Ghent, dark purplish rose)   Good   85%
'Royal Lodge' (Exbury, red)   Good   75%
'Scarlet Pimpernel' (Exbury, red)   Good   75%
'Strawberry Ice' (Exbury, pink)   Good   75%
'Sugared Almond' (Exbury, pale pink) Good   75%  
'Surrey' (Exbury seedling group)   Good   80%
'Sussex' (Exbury seedling group)   Good   80%
'Toucan' (Knap Hill, white) Good   75%  
'York' (Exbury seedling group)   Good   80%

 

Deciduous Azalea
  Average
Bud Hardiness
Average
(mathematical)
% of sun
best results
Species Zone5 Zone 6 Zone 5 Zone 6
alabamense (white) Fair Good 75% 80%
albrechtii (rose) Poor to Fair Good 65% 80%
amagianum (reported "difficult") (red) Poor Fair 60% 80%
arborescens (white, late) Good Good 100% 90%
atlanticum (white, dwarf) Fair to Good Good 75% 80%
austrinum (yellow) Fair Fair to Good 75% 85%
bakeri (yellow, orange, red, late) Good Good 80% 70%
calendulaceum (yellow, orange, red) Good Good 90% 85%
canadense (lavender, early) Good Good 85% 85%
canescens (pink) Poor to Fair Fair to Good 80% 85%
cumberlandense (yellow, orange, red, late) Good Good 90% 90%
japonicum (yellow, orange, red) Good Good 85% 90%
luteum (yellow)   Good   80%
oblongifolium (white) Fair to Good   80%  
nudiflorum (pink) Good Good 90% 85%
pentaphyllum (rose-pink) Poor   75%  
prunifolium (red, orange) Poor to Fair Poor to Good 80% 80%
quinquefolium (white) Poor   65%  
reticulatum (lavender) (reported "difficult") Poor Fair 65% 80%
roseum (pink) Good Good 80% 80%
schlippenbachii (pink) Good Good 75% 80%
serrulatum (white, late) Fair to Good   75%  
speciosum (red, orange, yellow) Poor Good 75% 85%
vaseyi (pink, early) Good Good 80% 90%
viscosum (white, late) Good Good 80% 80%
weyrichii (rose-red) (reported "difficult") Poor Fair to Good 65% 75%

 

Persistent Leaved Azaleas
  Average
Bud Hardiness
Average
(mathematical)
% of sun
best results
Persistent Leaved Zone 5 Zone 6 Zone 5 Zone 6
'Amoena' (Kurume, violet-red)   Poor to Fair   60%
'Big Joe' (Gable, reddish violet)   Good   60%
'Billy' (Gable, pink)   Poor   75%
'Boudoir' (Gable, violet-red) Fair Good 75% 75%
'Campfire' (Gable, red)   Poor   50%
'Carmen' (Kaempferi, pink)   Good   75%
'Cherokee' (Gable, orange-red)   Poor   50%
'Corsage' (Gable, lavender) Fair to Good Good 65% 75%
'Edna' (Gable, pink) Poor   75 %  
'Elizabeth Gable' (Gable, red) Poor Poor 75% 75%
'Esther Reiber' (Pride, light lilac) Good   75%  
'Fedora' (Kaempferi, dark pink) Fair to Good Good 75% 60%
'Geraldine Vuyk' (Vuykiana, red) Poor   75%  
'Grenadier' (Gable, scarlet)   Fair   60%
'Herbert' (Gable, reddish violet) Poor to Good Fair to Good 60% 60%
'Hexe' (syn: 'Firefly')        
'Hino-crimson' (Kurume, red) Poor Poor to Fair 55% 65%
'Hinodegiri' (Kurume, crimson) Poor Poor to Fair 45% 60%
'Hinomayo' (Kurume, pale pink)   Good   60%
'James Gable' (Gable, red)   Good   60%
'Joseph Gable' (Pride, white) Good Good 90% 80%
'Jessie Coover' (Gable, violet-red, double)   Poor   50%
'J. T. Lovett' (syn: 'Macrantha') (orange-red)   Poor   50%
kaempferi (species, orange-red)   Fair to Good   75%
kaempferi hybrids Poor to Fair   65%  
'La Roche' (Gable, magenta-red)   Poor   60%
'Lilac Time' (Kaempferi, violet-red)   Good   85%
'Louise' (Kaempferi, dark pink)   Good   80%
'Louise Gable' (Gable, salmon) Poor to Fair Poor to Good 50% 60%
'Lorna' (Gable, pink) Poor to Good Good 65% 75%
'Kathleen' (Kaempferi, rosy red)   Good   80%
'Marjorie' (Gable-Pride, Pink) Fair to Good   90%  
'Maryann' (Gable, violet-red)   Poor   60%
'Mary Dalton' (Gable, orange-red)   Poor   50%
'Maxwellii' (pulchrum form, carmine)   Fair   60%
'Mello-Glo' (Dawson, violet-red)   Good   60%
'Mildred Mae' (Gable, reddish violet) Poor to Good Good 50% 60%
'Mucronata' (syn: 'Ledifolia Alba') (white)   Fair to Good   75%
'Nadine' (Gable-Pride, pink) Good   75%  
'Norma' (Kaempferi, violet-red)   Good   60%
'Old Faithful' (Gable, reddish violet)   Good   60%
'Othello' (Kaempferi, reddish rose) Fair Good 75% 80%
'Palestrina' (syn: 'Wilhelmina Vuyk')        
'Purple Splendor' (Gable, purple)   Fair   50%
'Red Bird' (Glenn Dale, red)   Good   50%
'Rose Greeley' (Gable, white)   Poor to Good   50%
'Rosebud' (Gable, violet-red, double)   Poor to Good   85%
'Royalty' (Gable, reddish violet)   Good   70%
'Sherwoodi' (Kurume, reddish violet)   Good   60%
'Snow' (Kurume, white)   Fair to Good   60%
'Springtime' (Gable, violet-red) Fair to Good Poor to Good 55% 65%
'Stewartstonian' (Gable, red) Poor Poor 50% 65%
'Suetsumi' (syn: 'Flame' (Kurume,        
'Susan' (Gable, pink)   Fair   50%
'Thais' (Kaempferi, violet-red)   Good   80%
Westcroft hybrids   Good   80%
yedoense var. poukhanense (Species, lilac) Good Good 90% 85%
'Yodagawa' (Form or yedoense var. poukhanense) (Species, reddish violet, double)   Fair to Good   65%

 

In order of frequency mentioned,
the best ("favorite") rhododendrons:
Zone 5 Zone 6
'Mrs. C. S. Sargent' 'Mars'
'Mucronulatum' 'Blue Peter'
carolinianum 'America'
'America' 'Beaufort'
'Caroline' 'Roseum Elegans
'Charles Dickens' 'English Roseum'
'Roseum Elegans' 'Salvini'
'Roseum Superbum' smirnowii
catawbiense racemosum
maximum 'Dr. H. C. Dresselhuys'
'Fanfare' 'Pinnacle'
  'Catawbiense Boursault'
 
In order of frequency mentioned,
the best ("favorite") azaleas:
Zone 5 Zone 6
'Fedora' 'Boudoir'
'Corsage' 'Caroline Gable'
'Louise Gable' vaseyi
'Dr. M. Oosthoek' japonicum
'George Reynolds' arborescens
'Joseph Gable' 'Lustre'
'Toucan' 'Redbird'
  'Desiree'

Editor's Note: Parentages and color descriptions in the foregoing lists are taken from The International Rhododendron Register. Many growers recommended shade to some extent for deciduous azaleas primarily to prolong the time the flowers are in good condition, especially for the newer British hybrids. Some shade for persistent leaved azaleas is described as aiding the plants to retain their flower buds in good condition through the winter.

Soil Preparation

        Among the growers using the conventional ingredients of topsoil, peat and sand, the mathematical average of proportions for the mix giving the best results:

50% Topsoil  39% Peat  11% Sand

Among the growers using additional ingredients, the mathematical average of proportions for the mix giving the best results:

18% Topsoil  30% Peat  18% Sand  34% Other Humus Sources (Leaf Mold, Compost, Rotted Sawdust, Rotted Manures)

EDITOR'S NOTE: There was provision on the questionnaire to indicate "No special preparation-natural soil without additions." Among all of the replies only two growers indicated that their natural soil produced satisfactory results without modification.

Mulching

        The mulches which produce the best results listed in the order of frequency mentioned, with the depth of the mulch stated as a mathematical average of the replies:

Oak Leaves, 4"
Ground Corn Cobs, 1"
Sawdust, 2"
Peanut Shells, 2"
Peat, 2"
Pine Needles, 3"
Serve-All, 1"
Black Polyethylene Plastic
Wood Chips or Shavings, 3"

EDITOR'S NOTE: There was provision on the questionnaire to indicate that no mulch is used. Not one grower indicated that he cultivates rhododendrons or azaleas without a mulch.

Watering

        Since municipal water supplies are usually neutral (pH 7.0), the question was asked "Do you use city water or a natural source of water?" The responses: 

55% City Water
45% Well, Pond or Stream

        Apparently there is no difficulty from loss of soil acidity clue to the use of municipal water, although the surprisingly large percentage of growers who use a natural source of water did not state that this had anything to do with their reason for doing so. All members indicated that they do irrigate their plants. It is usually thought that irrigation of Rhododendrons and Azaleas during the month preceding the first expected frost impairs their hardiness by diluting the carbohydrate concentration in the sap. The question was therefore asked: "Name the latest date in the season prior to frost that you consider it safe to irrigate." The answers, average mathematically:

Zone 5: August 14th
Zone 6: September 6th

Fertilizing

        The fertilizers which produce the best results, listed in the order of the frequency mentioned:

Ammonium sulphate
Cow manure
Cottonseed meal
Agrico for Broadleaf Evergreens
Westcroft's Greenleaf Compound
Kapco Evergreen 7-7-7
Sheep manure
8-6-6
Eastern States Starter
G. & O. Azalea Fertilizer
Ammonium Sulphate plus 0-25-25
Cottonseed meal plus 0-15-15
5-10-5
30-10-10
8-8-8 (organic)
16-8-8
6-8-0
Ureaform

        It is usually thought that fertilizing Rhododendrons and Azaleas within 60 clays of the first expected frost impairs hardiness by stimulating unseasonably late growth. The question was therefore asked, "Name the latest date in the season prior to frost that you consider it safe to fertilize." The answers, averaged mathematically:

Zone 5: July 15th
Zone 6: June 18th

EDITOR'S NOTE: There was provision on the questionnaire to show that the grower did not use any fertilizer. Only one did not. It is interesting to note that growers in zone 6, where the first frosts are a good deal later than in zone 5, are much more conservative in extending the season of fertilizer use. Many of our members in zone 6 are professional growers.

Spraying and Dusting

        The insecticides which produce the best results, listed in the order of frequency mentioned:

Malathion
DDT
Dieldrin
Lindane
Aldrin
Aramite (miticide)
Nicotine and soap
Methoxychlor
Tedion
Vapotone XXX
DX

        The fungicides which produce the best results, listed in the order of frequency mentioned:

Captan
Fermate
Sulphur
Parzate
Karathane
Fixed Copper

EDITOR'S NOTE: Malathion as an insecticide and Captan as a fungicide has no serious competition in the preference of growers. 23% of the growers stated that they do no spraying or dusting whatever.

        I recommend that the portion of the survey relating to the bud hardiness of rhododendrons and azaleas, both hybrids and species, be repeated in 1963. Many growers commented that they had not grown some of the newer hybrids and rarer species long enough to have a valid opinion of their bud hardiness, and declined to rate them until they had more experience with them.


Volume 15, Number 4
October 1961

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