'ESEARO.C1- PSULTS FOIR FLOTM-MRGRMER
Azalea Studies19601 1971
Forticulture Series Mo. 19
Auburn, Alabama
CONTENiTS
Page
1. Influence of Photoperiod, Temperature, and Node Position on
Vegetative Shoot Growth of Greenhouse Azaleas, Rhododendron
ev. . * a .. . . .. . .. . . a . .t . . . . . 1
2. Effect of Photoperiod and Node Position on Shoot Development In
Greenhouse Forcing Azaleas, Rhododendron cv., Red American
Beauty . . . . ........... . . . . . . . . . . 7
3. Effect of Mist and Photoperiod on Shoot Development in Greenhouse
Forcing Azaleas, Rhododendron cv. . . . . . . . .
4. Evaluation of Several Growth Regulators on the Rooting of Three
Azalea Cultivars . ........... . ........ . . . 13
5. Comparison of Various Morphactin Sprays and Node Position on Mean
Shoot Length of Azalea cv. Kingfisher...... . . . . . . . 15
6. Effect of Various Growth Pegulator Sprays on Shoot Development of
Azalea, ev. Kingfisher . . . . . . ... a............. 17
7. Evaluation of Several Growth Retardants on Azaleas . . . . . . . 19
8. Rooting Response of Azalea Cuttings Treated with Various Growth
Regulators . . . . ............... . . . . . . . . . 21
9. Chemical Pinching of Azaleas with Ethrel and Off-shoot-0 . . . . 24
10. ChemicaliFlowering of Azaleas . . . . a. .. . .. a a* a. . 26
Influence of Photoperiod, Temperature, and Node Position on Vegetative
Shoot Growtth of Greenhouse Azaleas, Rhododendron cv
I/
William E. Barrick and Kenneth C. Sanderson
Nature of Work: The commercial azalea is grown as a pinched plant, thus maximum
groiw7th has to be made within a series of 2-3 pinches prior to flower bud
development. The importance of shoot growth is emphasized by grading standards
which specify a minimum number of flowering shoots per plant. The objectives
of this study were to determine the effect of photoperiod and temperature regimes
applied after shearing and node position (counting from the apex or shearing
point) on vegetative shoot growth. Experiments were conducted in environmental
chambers and greenhouses using the treatments showvn in Tables 1 - 5.
Results: Generally, an increase in shoot length (Tables 1 and 2) and shoot dry
weight (Table 3) and a decrease in number of shoots per lateral branch (Tables
1 and 2), with no effect on number of leaves per shoot (Table 3), was observed
on sheared azaleas grown under increased daylengths in environmental chambers
or greenhouses. Plants grown at low (24 - 180 C.) temps in environmental
chambers had greater shoot lengths, higher number of shoots, more leaves per
shoot, and shoot dry weight occurred as node position for shearing increased
(Tables 4 and 5). Thus, an Inverse relationship apparently exists between
node position for shearing and shoot growth in greenhouse azaleas. It is
suggested that some environmental or chemical means be found to overcome apical
dominance in order to stimulate shoot development from all positions regardless
of their nearness to the shearing point or shoot apex.
I/ Former graduate students and Associate Professor, Agr. Exp. Sta. Auburn
Univ. Mr. Barrick's present address: Dept. of Horticulture, Michigan
State Univ., East Lansing, Michigan 48823. Appreciation is expressed to
Dr. R. *. Patterson, Data Analyst, Auburn Univ., and Yoder Brothers,
Barberton, Ohio.
Table 1. Mean -Shoot growth of azalea at various photoperiod
and temperature treatments in environmental chambers
Cultivar Experinent Temperature (C)
.K.ingfisher
Kingfisher
Aver"--ge
Red Wing
Kingfisher
Kingf isher
Av e ra ge
24-18
35-29
24-18
24-18
29-24
4
0
6
5
hLot operiod
Shoot length a(mmm)
z 14 V
;5,7c 71,.)b 8&
S5.Oc 69 *5b 8-
'5..3c 70. 3b 13(
6. lc 48,2 b 6 "e
12 2
31.4a
4 1. 2
30. 3a
41 .7b
4f Average
7
0
2a 74,6a-
5O4a 7.33a
6, 3d
2,6a 490
4 Averap
9.2a 54,5a
705a 33.lb
8. 3a
9
2 .I
2.3
2. 2~
2.
8
4..
2.0s
3.0Oa
P'hotoperiod
Number of s~hoots
14 24
a 2. Oa 1. 9a
1 2. 2a .2. 2a
a 2. la 2,.Oa
1 2. la 2.1a
12 24
394b 395b
I l.9a l.Sa
I 2.7b 2,6b
Z Basic photcperiod of 8 hr. (26,910 lux) supplerment ed with
or 16 hr. (24 hr.).0
(646 lux) 4 hr. (12 hr.) in the middle of the nifght
Y Mean separation, in rows for cultivar (experiment) and -photoperiod average and in coluns
averages, by Duncan's multiple range test at the 
5%K level.
for temperature
Average
2. Oa
2. 2a
2.1
Averag
3 .7a
1, 9b
?... .. c.....s
n
1
2
.:......
Table 2. Shoot growth of azalea at various photoperiods in greenhouses
Cultivars Experiment Photoperiod Photoperiod
Shoot length (mm) Number of shoots (mm)
9
z  
14 24 14 24
Kingfisher &
Roadrunner I 64.2c
y  
69.9b 72,6a 3.3a 3.1b 3.0b
Pedwing 2 34.8c 39.6b 
46.2a 2.4a 2.5a 2.5a
8 12 24 8 12 24
Kingfisher 3 25.8a 30.2a 27.7a 2.5a 2.2b 2.lb
Ped American Beauty 4 31.8a 39.3a 41.7a 7.9a 7.3a 7.4a
z
Natural photoperiod 
(9 or 8 hr.) supplemented 
with incandescent 
light in
the middle of the night (14-12 hr.) and at end of controlled natural
period (24 hr.).
Y Mean separation, in rows, by Duncan's multiple range test at the 5% level.
Table 3. Grow~th
photoperiod
variables of azalea, cv. Ringfisher, at indicated
a ind teitmperature treattients in environmental
chambers, ExLperiments 4 and 5
M.W WOOIl'' -- m"
0
Vegetative growqth Photoperiod Tmeature(C) Ave rage
24-18 29-24
Murvber of leaves 8 6.2-a y3.7b 4. 9b
12 5.7a 3,9b 4.8b
24 6.5a 5.Oa 5.8a
Average 6.1a 4.2b
Dry Tot. 8 
0.07c 0911b O.09b
12 0*09b 0.1% 0,10b
24 0.12a 0.16a 0.14a
Average 0 .09b 0. 13a
z Basic photoperiod of 8 hrM. 
(26,,910 lux) supplemented
the middle of the night or 16 hr. (24 hr..) .
Writh (646 lug) 4 hr.
YMean separation, in columns and rows, by Duncan's multiple. range test
at the 5% level,
Tablec 4. Growrth
node positions
varables of azalea, cv. Kingfisher, at indicated
in enivironmental chaib era, Experiments 4 and 5
Vegetative growth No d e Tnrat~ire (
0
C). Average
24-18 29 24
Shoot length (mm) .1 68.5a z 66.7a 67.6a
2 7
0
.3a 67.5a 68.9a
3 63.2ab 45*Ob 5491b
4 52.6bc 7.2c 29.9c
5 50.1c 11.9c 31.Oc
6 .22.ld O.Oc I11
Number of shoots
1 6.Oa 6.Oa 6.Oa
2 5.8ab 396b 4.7b
35*3b 1.4c 3.4c
4 2.9c Oeld 1.5d
5 194d Ow2d 0.8e
6 0.6e O.Od O.3f
Number of leaves 1 8.6a Co.5a 9.1a
2" 7*9ab 7* 9b 7. 9b
3 70%b 5.4c 6.2c
4 5.5c Oe9d 3o2d
5 5'. 10c 1.4d 3.2d
6 2*8d o.Od 1.4e
Dry vt. (R,)
1 0.15a O.22a O.19a
2 0.13a O.22a O*l7ab
3. O*09b f0.20a O.15b
4 f.O6be 0 eO4b. O.O5cd
5 O.O7cd O.07b 0.07c
6 O,04d 0.00% O.02d
z
fean separataion, in columns, by Duncan's multiple range test at 5% level.
6
Table 5. Growth variables of Azalea at various
node posit ions in greenhouses
Mode Shoot Numb er Numb er Dry
length of 
of wto.
(mi') Aloots leaves (g)
Exp, 3 cv. -Kingfisher
1 49.0aZ 5.8a 8.5a 0,14a
2 54.7a- 4.9b 7.7a 0.13a
3 41. 4b 2.1c 5 .9b 0*07b
4 9.8c 0.34. 1.3c 0.Olc
5 l0.8c 0.3d 1.2c Q.Olc
6 1.84 0.04 0.2d 0.00C
Ex.4 cv., Red Aerican
Beat
1 57.1a 7.7a 7.7a 0.17a
2 55.6a 7.8a 7.Oab 0913b
3 52.8a 7 -,lb 6.lbc 0.l0bc
4 51.5a 2,6d 5.3c 0.09C
5 48.6a 3.3c 5.3c 0XO8c
6 8.5b 0,le 0.8de 0.02e
7 21.7b 0.4e 2.64 0.O7cd
8 16.8b 0.3e 1.
9
e 0.O3de
zMean separation, 
in columns for
range t es t at 5 % level.
experiment . by Duncan's multiple
Publications:
Barrick, W. E. and K, C. Sanderson. 1973. Influence of photoperiod,
temperature and node position on vegetative shoot growth of greenhouse
azaleas Rhododendron cv. J. Amer. Soc. IHort. Sci. 98(4).
I7
Table 6. Growth of Red American BeaUty Azaleas as influenced by
mean shoot2- length, number of shoots, and number of leaves,
at indicated photoperiodic treatments
photoperiod
(hr.)
8 .
12
16
20
24
844 (in middle of night)
Shoot
length
mm
z
31.83a
39. 3a
43. 89a
37.,44a
41.71a
39. 31a
Vegetative growth
Ju-mber of Number of
shoots leaves
No.NO.
7.88a 4.19a
7.31a 4,49a
7.06a, 4.80-a
6.81a 4,30a
7.44a 5.00a
7.25a 4.73a
16............... 4,9 06
z
Means in columns followed by the sae letter are not sinif icantlY different
at 5% level.
PublI-ications
Barrick, TT. E. and K C. Sanderson. 1973. Effect of photoperiod and node
position on shoot development in greenhouse forcing azaleas, Rhododendron
cv. Red American Beauty. (Submitted for publication),
Dry wt.
g
0.0 70a
0 .0 87a
0. 085a
0.081a
0.104a
o0.090a
...
O i A " " " " " "
Effect of Mist and Photoperiod on Shoot Development
in Greenhouse Forcing Azaleas, Rhododendron cv
William E. Barrick and Kenneth C. Sanderson
Nature of Work: Effects of photoperiod and 
mist treatments applied after
shearing on shoot development were studied 
on forcing azalea cultivars,
'Gloria', 'Red Wing','Coral Bells' and 'Anytime' grown in a lightly
shaded greenhouse under prevailing 
summer temperatures. Treatments 
in-
cluded: (1) mist with supplemental light, (2) supplemental 
light only,
(3) mist only, and (4) check -
which received neither. A mist 
line above
the greenhouse bench provided intermittent mist (2.5 sec. 
of mist every 100
sec.) between 8:30 a.m. and 4:30 p.m. 
Natural light occurred from 8:30
a.m. to 4:30 p.m. Supplemental 
light used to extend this 8 
hr. daylength was
provided by 3 100-watt 
incandescent light 
bulbs placed 83 cm 
above each bench
to give a light intensity of 
40-55 ft-c measured with a Weston 
756 illumination
meter with quartz filter at the rim of the pot. 
Black cloth separated lighted
from non-lighted benches. Shoot number 
and length were determined 8 weeks
after shearing.
Pesults: Shoot number and length were not increased 
under supplemental
light and mist treatments (Table 7). Cultivars 
differed in shoot number and
length. Misted plants were darker 
green and more luxuriant than non-misted
plants.
1/ Former graduate student and Associate 
Professor, respectively, Agr. Exp.
Sta. Auburn Univ. Mr. Barrick's present address: Dept. of Hort. 
Mich.
Sta. Univ. East Lansing, MI. Appreciation is expressed to R. 
M.
Patterson, Data Analyst, Auburn Univ. Agri. Exp. Sta., and 
Blackwell's
Nursery, Semmes, AL.
Table 7. Vegetative growth of azalea cultivars as influenced by
photoperiod and mist
Treatment Cultivar Mean
'Ped 'Coral 'Any-
'Gloria' Wing' Bells' time'
Number of Shoots
Supplemental light, mist. . ... 2.4 2.1 2.6 2.4 2.4a
Supplemental light only . .. 2.2 2.1 2.4 2.2 2.2a
Mlist Only ............ 2.3 2.3 2.4 2.3 2.3a
Check ............. 2.3 2.1 2.3 2.2 2.2a
Mean .... .............. 2.3ab 2.2b 2.4a 2.3ab
Shoot Length (nam)
Light, no mist ........... 67.0 54.1 35.5 54.0 52.8a
Light, no mist0 . ...... 59.6 62.9 48.5 58.6 57.4a
No light, mist ........ 63.4 49.0 37.8 43.7 48.5a
No light, no mist ....... 66.9 46.6 32.8 48.5 43.7a
Mean ............ 64.2a 53.1b 38.7c 51.3b
z
Means in rows followed by the same letter or letters are not significantly
different at the 5% level. Interactions were not significant.
Publications:
Barrick, W. E. and K. C. Sanderson. 1973. Effects of mist and photoperiod
on shoot development in greenhouse forcing azaleas, Rhododendron, cv.
(Submitted for publication).
10
Evaluation of Several Growth legulators 
on the
Rooting of Three Azalea Cultivars
Terril A. Nell and Kenneth C. Sanderson
Nature of Work: The use of root inducing substances in the-propagation of
vegetative cuttings has become an accepted commercial practice. Research
in the 1930's revealed that indole-butryic acid and napthalene acetic were
the most effective root inducing chemicals- however, the search for new
materials continues. Several new chemicals have recently become available
and this research's objective was to evaluate several of these chemicals
as root-inducing substances on azaleas.
Four-inch softwood cuttings of the azalea cultivars Evensong, Kingfisher
and Red American Beauty were cut at an angle to the plane of the stem
and the base of the cutting dipped for 5 sec. in one of the following
liquid treatments: (1) check, no treatment! (2) 2,500 ppm B-Nine; (3) 50 ppm
Bayer 102612; (4) 40 ppm 2,4-D;; (5) 125 ppm Ancymidol (6) 1,000 ppm
Ethephon; (7) 1,000 ppm Nia 10637o (8) 1,000 ppm NAA; (9) 5,000 ppm NAA;
(10) 1,000 ppm Uni-F 529. Propagation was carried out in a 1:1 sandand
vermiculite media under mist and Twith bottom heat. Cuttings were graded 8
weeks after sticking as follows: 0 = no rooting, 1= callused, 
no roots, 2 sum
poor rooting, 3~ average rooting, 4 *O good rooting, 
5. = excellent rooting.
Resuts:Bayer 102612 burned the apical meristem on Evensong and Rted
American Beauty and cuxrled the leaves on Kingfisher 3 weeks after treatment.
NAA at 1,000 ppm pDroduced the largest q'uantity of roots on E.vensong and
11
Nia 10637, Ancymidol and Ethephon showed promise as root inducing sub-
stances, and further research is warranted. Cultivars differed statistically
in rooting with Kingfisher' and'Evensong yielding the best and poorest root-
ing scores, respectively.
This investigation demonstrated the value of choosing a cultivar that
produces a good quick root system. The choice of a root inducing substance
was dependent on the cultivar. Other researchers have shown that growth
retardants such as B-Nine, Uni-F 529, Ethephon and Cycocel have root inducing
properties; however, more research is needed on these compounds and materials
such as Ancymidol and Nia 10637.
Pub lications
Mell, T. A. 1971. The Effect of Several Growth Regulators on the
Rooting of Three Azalea Cultivars. Proc. So. Agr. Workers. 68th. Ann.
Conven. 189.
Nell, T. A. and K. C. Sanderson. 1972. Effect of Several Growth
Regulators on the Rooting of Three Azalea Cultivars. Florist Rev. 150:
21-22, 52-53.
Comparison of Various Morphactin Sprays and Node Position on
Mean Shoot Length of Azalea, cv. Kingfisher
Kenneth C. Sanderson and William E. Barrick-
Nature of 1Work: Morphactins constitute a new group of plant growth regulators
which influence growth iatterns of plants. Concentration determines effect;
however, morphactins have been reported to dwarf, delay and inducing branch-
ing in plants. Six-inch pot size'Kinfisher' azaleas were sprayed with the
morphactins listed in Table 8 on March 23, 1970. The plants were sheared 4
1/ Associate Professor and former student, respectively, Dpt. of Hort., Agr.
Txp. .ta., Auburn TUniv. M"r. Barrick's present address: Dept. of Hort.,
Michigan State Univ., East Lansing, MI.
12
weeks prior to spraying. Six lateral branches on 6 plants were selected
for data at 6 node positions (node position . was closest to the shearing
point and node 6 the furthest). Data on shoot length were taken May 19, 1970.
The plants were grown in a shaded fiberglass greenhouse during the experiment.
Results: Morphactins at the concentrations used in this experiment caused
severe distortion of the leaves on azaleas. The distortion was still evident
approximately 9 months after treatment. Leaves appeared crinkled and mis-
shapen. New leaves were smaller in size and initially light green in color.
The Bayer 102614 had the greatest shoot length (Table 8). Ortho's 'aintainlI
had the shortest shoots. The Bay 102614 produced longer shoots at node 2
than at node 1 (counting from the shearing point) at both 50 and 100 ppm. How-
ever, in most cases, an inverse relationship between node position and shoot
length existed. Shoot length decreased with increases in node 
position.
Further research is warranted on the influence of morphactins on shoot develop-
ment in azaleas.
Table 9. Comparison of various morphactin sprays on mean shoot
length (am) at various nodes on azalea, cv. Kingfisher
Treatment Node Men
1 2 3 4 5 6
Check . . . . . . . . . 34.5 30.7 15.7 2.6 5.6 3.0 15.4
100 ppm Bay 102612 . . 7.1 6.0 1.3 0.0 0.0 1.1 2.6
100 ppm Bay 102613 . . 1.1 1.0 0.4 0.7 1.6 15 1.1
100 ppm Bay 102614 . . 28.3 34.7 15.5 6.6 1.9 0.3 14.6
100 ppm Ortho . . . . . 0.8 0.4 0.1 0.0 0.0 0.0 0.2
50 ppm Bay 102612 . . . 0.0 0.2 0.2 0.3 0.4 0.3 0.4
50 ppm Bay 102613 . . . 2.1 8.1 6.6 3.0 2.7 1.3 4.0
50 ppm Bay 102614 . . . 36.2 44.1 14.1 1.0 1.2 0.2 16.1
50 ppm Ortho . . . . . . 1.0 1.6 0.3 0.1 0.0 0.0 0.5
Mean . . . . . . . .. 12.4 12.7 6.0 1.6 1.5 0.9 5.9
Publications: None
13
Effect of Various Growth ~egulator Sprays on Shoot
Development of Azalea, cv. Kingfisher
1/
Kenneth C. Sanderson
Nature of Work: Growth regulator sprays evaluated on shoot development of
azaleas were 10 ppm Bayer 102613, 50 ppm Bay 102613, 5,000 ppm B-Nine,
2,500 ppm Ethephon, 6 ppm Ancymidol, 23 ppm Ancymidol, 6,000 ppm Niagara
10637, 2,500 ppm UTI-F-529. Liners of the azalea cultivar Kingfisher were
sprayed 4 week after shearing with a mist blower until the leaves glistened.
Five lateral shoots were measured prior to retardant spraying and then re-
measured at the end of the experiment. There were four plants per treatment
and two replications. The experiment was conducted in a fiberglass greenhouse
with a light intensity of approximately 5,000 ft-c. The retardant sprays were
applied on July 31, 1970, and measurements were made on October 7, 1970.
Results" Bay 102612 and Niagara 10637 distorted the leaves of the azaleas.
Bay 102613 at 50 ppm yielded the least increase in shoot length (Table 9).
Check plants had the greatest mean increase in shoot length (2.11 cm). All
retardants except Ancvmidol at 6 ppm reduced shoot length.
/ Associate Professor, Dept. of Hlort., Agr. Exp. Sta., Auburn Univ.
14
Table 9.Compairson of various growyth retardant sprays
on shoot development of azalea, cv. Kingfisher
Treatment Increase in shoot
length (CM)
Check . a. 41 0, .* 0 .0 0. .0 . .40 . . 2.11
10 ppm Bayer 102613 ....... ..... 1.74
50 ppm Bayer 102613................ . . .6. .54
5,000 ppm B-Nine0a. .l.b..0.a.a.#. .0. .1.70
2,500 ppm. Ethephol ... 3.... . .... 3
6 ppm Ancymidol 4 4 0 . A 0 6)0 #A . 0 0 a 02.00
23 ppmAncyiddl 1....8.......4
1,OQ0 ppm Niagara 1063711. .7... ....
6,000 ppm Niagara 10637 ........... 53
2,500 ppm Uniroyal F 529 ...... ..... 33
Publications None
Evaluation of Several GrowTth Retardants on Azaleas
1/
Kenneth C. Sanderson
N a t ure of Work: 'Kingfisher
4 
azaleas, 6Anch potted plants, received the follow-
ing spray treatments on August 16, 1971: (1) check, none, (2) 100 ppm Ancy-
midol, (3) 200-ppm Ancymidol, (4) 3,000 ppm. Cycocel, (5) 1,500 ppm B-Nine,
(6)1,500 ppm Uni-F 529, (7) 750 ppm B-Mine plus 750 ppm tni-F 529, (8) 200 ppm
Nia (Niagra) 10637, (9) 200 ppm Nia 10656, (10) 1,500 ppm Gycocel plus 750 ppm
B-Nine, (11) 2. 5g/liter Dupont DPX and 
(12) l.25g/liter IPX.
Results: Phytotocicity was observed with Gycocel and DPX, Gycocel caused a.
severe chlorosis of the leaves when applied alone or -in combination with B-Nine
Dupont's DPX ,caused the new leaves to be rolled upward, off color and severely
reduction without injury. and deserves further study.
1/ tAssociate Professoro Dept.. of Hort., Agr. Exp. Sta.,. Auburn Univ.
15
Table 10. Mean shoot length of Kingfisher azaleas after
treatment with various growth retardants
Treatments Mean shoot length (cm)
Check . . . . . . . . . . . . . . . . . . . . . . 8.5
100 ppm Ancymidol ...... . . . . . ........ 7.2
200 ppm Ancymidol . ......... . . . . . . . 7 .9
3,000 ppm Cycocel ............... . . 6.0
1,500 ppm B -Nine . . . . . . . 9.0
1,500 ppm Uni-F 529 ............ . . . . . .. 8.3
750 ppm B-Nine plus 750 ppm Uni-F 529 . . . . . . . 7.4
200 ppm Nia 10637 . . . . . ... 6.4
200 ppm Nia 10656 ......... . ........ . 7.0
1,500 ppm Cycocel plus 750 ppm B-Nine . . . . . . . . 6.3
2.5g/L DPX ...... . . ............. 4.0
l.25g/L DPX ....................... 4.4
z/ Plants sprayed until run-off.
x/ Mean of 25 shoots from 5 plants selected at random from 3 replications.
Publications: None
Rooting Response of Azalea Cuttings Treated
with Various Growth Regulators
1/
Kenneth C. Sanderson
Nature of Work: Three experiments on root-inducing compounds were conducted
on azaleas, cv. Evensong during May to Oct. 1970, in a lightly shaded
greenhouse. Propagation was carried out under mist (2.5 sec. every 100 sec.
8 a.m. to 4:30 p.m.) using a 1:1 sand and peat media with bottom heat
(70 degrees F.). All liquid treatments were applied as 5 sec. dips. Follow-
ing rooting, cuttings were scored for rooting using the following relative
scoring system for each experiment and species: 0 = dead; I = alive, not
callused; 2 = callused; 3 = light rooting; 4 = medium rooting and 5 = heavy
rooting.
Experiment I. Cuttings received the following basal dip treatments
(10 per treatment) prior to sticking: (I) none; (2) Hormodin No. 2; (3)
1,000 ppm Ethephon; (4) 2,500 ppm B-Nine; (5) 50 ppm Bay 102612 and (6) 1,000
ppm IBA. Cuttings were treated and stuck on May 21, 1971. Treatments were
1/ Assoc. Professor, Dept. of Horticulture, Agr. Exp. Sta., Auburn Univ.
16
replicated. twice Records were taken after 8 weeks.
E~eriuent_2. On August 7, 1970 the following treatments were applied
to cuttings: (1) none; (2) 1,000 ppm Ethephon (3) 2,500 ppm B-Nine; (4)
1,000 ppm Uni-F 529* (5) 40 ppm 2,4,5-TB; -(6) 50 ppm Bay 102612 (7) 1,000
ppm Ilia 10637; (8) 125 ppm Ancymidol (A-Rest); (9) 1,000 ppm IBA and (10)
59000 ppm IBA, Five cuttings were used in each treatment which was replicated
twice. Rooting scores were recorded after 8 weeks on October 7, 1970.
Experiment 3. Various strengths of 3 commercial root-inducing compounds
were compared with 2,495 TP, B-Nine and Ethephon-for root inducing activity.
Treatments applied on May 14, 1970 we-re (1) check- (2) Hormodin No. 1*
(3) Hormodin No. 2; (4) Hormodin No. 3; (5) Rainbow Tender. (6) Rainbow
Woody; (7) Rootone; (8) Rootone No. 10; (9) 5 ppm 2,4,5-TP* (10) 40 ppm
2,4,5-TB' (11) 1,000 ppm Ethephon; (12) 2,500-ppm B-Nine. Treatments were
replicated twice using 5 cuttings per treatment.,Rooting scores were recorded
after approximately 8 weeks,
Results: Hormodin No. 2 yielded the highest rooting scores in Experiment 1
(Table 11). Cuttings treated with flay 102.612 averaged the poorest rooting
scores. In Experiment 2, azalea cuttings rooted best when treated with 125
ppm Ancymidol, 40 ppm 2,4,5-TB and 1,000 Ethephon (Table 11).
No treatment, Hormodin No. 1, Hormodin No. 3, Rootone and 2,500 ppm
B-Nine produced the best overall rooting scores in Experiment 3 (Table 11).
Rootone and the check scored the highest rooting for azalea cuttings in
17
Table 11. Rooting scores of azalea, khododendron cv. Evensong, cutting
treated with varIous growth regulators. Experiments 1-3 2/
Treatment Experiment
2 3
Ch e k *....0.0.0 ..e......* 4.3 4.0 
3.7
'Hormodin No. 1 . . ... . .. . 3.3
Hormodin No. 2 .. . .4.6 2.6
Hrmodn No. 3 -2.9
1,000 ppm Ethephon ....... 3.82 27
1,000 ppm IBA ......... 3.7 4.
5,00 ppm IBA . . . . .4.1
50 ppm BAY-1l062 61 . .9. . 2.3.5
2,500 ppm B-Nine .... 3.8 35 33
1,000 ppm UNl-F529.4,.
5 ppm 2,4,5-TP ...... 27
40 ppm 2,4,5-TP-4.3 2.6
1,000 ppm NIA-10637 3.8
125 ppm Ancymidol -4.4
Rainbow Tender 3.0
Rainbow Woody-2.8
Rootone -3o6
Rootone No. 10 3.0
He an 3.8 4.0o 3.0
2/ Cut111tings were rated: 0= dead, 1 alive, not rooted or calluses,
2= callused, 3= light rooting, 4 . medium rooting, 5 heavy
rooting.
The outstanding root-inducing 
properties of Ethephon are the 
most
important findinags of this research. Ancymidol, 
Bay 102612, Mia 10637,
2,4 5-TP and B-Nine also had exceptional root 
inducing properties in some
instances. Further testing of all these 
materials is needed.
Publications: None
18
Chemical Pinching of Azaleas with Ethrel and Offshoot-0
Kenneth C. Sanderson and William E. Barrick 1/
Narature of Work: Ethrel, a new growth regulator, has been reported to
exert a synergistic effect on the action of other growth regulators.
Experiments were conducted on azaleas to determine the effect of Ethrel
alone and in comabination with the chemical pinching agent, Offshoot-0,
on the number of breaks per shoot. One experiment was conducted on the
cultivar 'Chimes' during September-October, 1969, and another experiment
was conducted on the cultivar 'Kingfisher' during March-May, 1970.
Treatments consisted of (1) hand sheared; (2) 2,500 ppm Ethrel spray; (3)
5,000 ppm Ethrel spray; (4) 2,500 ppm Ethrel plus 3.5% Offshoot-0 spray;
(5) 5,000 ppm Ethrel plus 3.5% Offshoot-0 spray; (6) 3.5% Offshoot-0
spray; and (7) 4.5% Offshoot-0 spray. Sprays were applied to run off with
a Halaby mist blower.
Results: A reddish discoloration of the leaves was observed on some leaves
in both cultivars of Ethrel treated plants. Older, lower leaves fell off
both cultivars soon after Ethrel spraying. Plants usually recovered from
leaf discoloration and produced new leaves after leaf drop. A combined spray
of 5,000 ppm Ethrel and 3.5% Offshoot-0 averaged the most number of breaks
(3.4) per shoot in 'Chimes'. 'Kingfisher' had the most breaks (2.9) when
sprayed with 2,500 ppm Ethrel plus 3.5% Offshoot-0. Fewest number of
breaks (2.3) per shoot was obtained with 2,500 ppm Ethrel in 'Chimes' and
with 4.5% Offshoot-O in 'Kingfisher' (1.6). A 5,000 ppm Ethrel spray
averaged 2.6 breaks in both cultivars. Both cultivars produced 2.8 breaks
when sprayed with 2,5000 ppm Ethrel plus 3.5% Offshoot-0. 'Chimes' and
'Kingfisher' had 2.9 and 2.6 breaks, respectively, when sprayed wtih 3.5%
Offshoot-O. A 4.5% Offshoot-0 spray yielded 2.8 and 1.6 breaks with 'Chimes'
1/ Former graduate student and Assoc. Professor respectively, Agr. Exp. Sta.
Auburn Univ. Mr. Barrick's present address: Dept. of Hort., Mich. State
Univ., East 
Lansing, 
11.
19
and 'Kingfisher', respectively. Ethrel sprays seemed to have some in-
fluence on the number of breaks produced. Combined with Offshoot-0,
Ethrel increased the number of breaks per shoot. The small increase in
breaks, cost of materials and initial plant damage would probably rule
out commercial use of the Ethrel-Offshoot-0 sprays.
Publications:
Sanderson, K. C. 1969. Growth Retardants for Florist Crops A to Z.
Florist Rev., Vol. 145, No. 3757. Annual Progress Reports available from
authors.
Chemical Flowering of Azaleas
Kenneth C. Sanderson
Nature of Work: The use of chemicals to induce flowering in azaleas has
required repeated applications of massive dosages and often has only
partially substituted for low temperature storage. It might be more
practical to reduce the number of applications by utilizing chemicals in
combination with short-term low temperature storage. Experiments were
conducted in 1970-71 with non-refrigerated plants and plants refrigerated
half the required time.
Shadehouse grown, budded, azaleas 25 cm top diameter, of the culti-
vars 'Redwing' and 'Roadrunner' were divided into two groups: (I) not
refrigerated, left in the shadehouse and (2) refrigerated at 450 F under
approximately 20 f.c. of light continuously for 3 weeks. On Oct. 30, 1970,
the plants were placed in a 620 F greenhouse and the following spray treat-
ments applied: (1) check, no spray, (2) 100 ppm NAA, (Naphalene Acetic
Acid), (3) 100 ppm KGA, (Gibberellic Acid Potassium salt), (4) 2,500
Ethephon, (5) 100 ppm NAA plus 100 ppm KGA, (6) 100 ppm NAA plus 2,500 ppm
Ethephon, (7) 100 ppm KGA plus 2,500 ppm Ethephon and (8) 100 ppm NAA, 100
ppm KGA plus 2,500 ppm Ethephon. Spray treatments were applied weekly for
3 weeks.
20
Results: The buds of 
all plants sprayed with 
Ethephon were killed 
with
4 exceptions, (Table 12). 
Ethephon also caused 
a reddish discoloration,
chlorosis of leaves and 
leaf abcission. Plants 
sprayed with WAA had 
the
best looking foliage 
and had the least leaf 
drop. Chemical sprays 
did
not cause earlier 
flowering in unrefrigerated 
plants (Table 12). Unrefrigerated
Redwing plants flowered 
almost as soon as refrigerated 
plants. A combination
of refrigeration and 
NAA plus KGA sprays 
caused the earliest flow,-ering 
in
RedwTing'azaleas. Refrigeration 
and UMA sprays caused 
the earliest flower-
Ing in 'Ptoadrunner 
azaleas .
Table 12. Days to flowering 
of treated azaleas
after placement in a.620'1? 
grenhouse
Zl
Treatment Ref rierated 3 weeks Non-refrierate
R~e dxing' oRoadrunner 
Redwinig -Roadruriners
Che ck,. no spray* .* 
.65
100 ppm 1AA .* 
.... 61
100ppm KGA 
.... *65
2,500 ppm Ethephon 
.. . Buds killed
100 ppm 14AA + 
100 ppm KGA 0 
. 58
100 upm NAA + 
2 9500 pp~m
Ethephon .. Buds, 
killed
100 ppm KGA + 
2,500 ppm
Ethephon'.. 
59
100 ppm K(GA + 
100 ppm NM 
+
2,500 ppm Ethephon. 
59
126
77
104
Buds killed
10.7
Buds killed
Buds killed
Buds killed
67 107
70 86
67 89
67 88
70 Buds killed
Buds killed Buds killed
Buds killed Buds killed
Buds killed Buds kil.ed
z/ Plants sprayed 
until runoff.