QBARS - v15n4 Summary of Replies to Questionnaire on the Best Rhododendrons, Azaleas and Methods of Cultivating Them in the Region Served by the Great Lakes Chapter

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.