September 1983 4
Horticulture Series No. 30
Auburn University
Agricultural Experiment Station
Gale A. Buchanan, Dean and Director
Auburn University, Alabama
t
y
RESEARCH RESULTS FOR ORNAMENTAL HORTICULTURISTS
Horticultural Series No. 30
Alabama Agricultural Experiment Station
Gale A. Buchanan, Dean and Director
Auburn University September, 1983
Auburn University, Alabama Kenneth C. Sanderson
Editor
CONTENTS
Growth of 'Hershey's Red' Azalea in Three Pot/Mulch Combinations.
Gary J. Keever and Gary S. Cobb . . I.......... ... . 1
Phototoxicity of Chrysanthemum to Sprays and Drenches of Dursban'
- A Potential Control for Leafminer, Liriomyza triffolii
(Burgess). Kenneth C. Sanderson and WTilis C. Martin, Jr. . . .. 
3
Cutting Propagation of Chionanthus retusus (Lindl. & Paxt.),
Chinese Fringetree. Fred B. Perry, Jr ................ 5
Effect of Growth Retardants on English Ivy, Hedera helix L.
Kenneth C. Sanderson, Willis C. Martin, Jr., anLih-Jyu Shu . . . 8
a
Growth of 'Hersheyls Red' Azalea in
Three Pot/Mulch Combinations
Gary J. Keever and Gary S. Cobb
Nature of Work: High-soil temperatures have been shown to reduce root
and shoot growth of plants. Research indicates that optimum root
growth for many plants occurs between 20-30
0
C 68-86
0
F) (1). Growth
is reduced at soil temperatures above 30
0
C (86 F) and will cease in
many species above 40
0
C (104
0
F) (2). Soil temperatures above 49
0
C
(120
0
F) have been observed in both green and black pots exposed to
direct solar radiation (3). This work was initiated to evaluate
temperature fluctuations and growth of Rhododendron 'Hershey's Red' in
3 pot/mulch combinations during the summer months.
In April, 1982, uniform 'Hershey's Red' liners were potted in 2.8
liter (trade gal.) black or white polyethylene pots in amended pine bark.
Three treatments were selected to determine pot/mulch 
effects on growth
medium temperatures and plant growth: 1) black pots on a white clam
shell mulch; 2) white pots on a black polyethylene mulch; and 3) black
pots recessed into a white plywood frame so that the pot sides were not
exposed to direct solar radiation.
Air and container temperatures were monitored continuously during
the summer months. In September, root coverage (%) of the surface of
the bark medium, relative root development, growth indices, and top dry
weight were determined.
Results and Discussion: Growth medium in the black pots on white mulch
consistently reached the highest maximum temperatures. Medium in white
pots on a black mulch averaged 5oC (9
0
F) cooler. This is consistent
with the findings of Whitcomb (4). Temperatures in the plywood frame,
which simulated jammed plants where pots are shaded, were lower than the
other two pot/mulch combinations and lower than ambient air temperature.
Maximum temperatures at the different locations within a single black
pot on white mulch decreased in the following order: south wall, west,
south, east, center, and north side. Maximum ambient air temperature
was lower than any of the maximum pot temperatures.
Percent root coverage of the growth medium surface was greatest for
plants grown in the plywood frame, followed by plants 
in white pots on
black mulch, and least with the black pot/white mulch combination (Table
1). Root coverage was greater on the north side of white pots on black
mulch than on the south side. Although not significantly different,
values indicated less coverage of the south side of black pots on white
mulch compared to the north side. Relative root development and 
growth
indices were greater in the plywood frame and in white pots 
on black
mulch compared to black pots on white mulch. Growth as measured 
by top
dry weight was 
greater in the 
white pots on 
black mulch than 
in
black pots on white 
mulch.
Lower temperatures 
and greater root 
and top growth 
in white pots
on black mulch suggest 
the need to reconsider 
black pot/white 
shell
mulch combinations 
commonly used in 
south Alabama. White 
pots on a
black mulch appear to provide 
a viable alternative for 
growers. Lower
temperaturesand 
better root 
development of 
plants in the plywood 
frames
suggest that it 
is beneficial to 
jam plants or to 
space plants so 
that
foliage minimizes 
direct solar radiation 
stricking the sides 
of pots
during the summer 
months.
Table 1. Root coverage (%) of the north 
and south bark surfaces, relative
root development, growth index, and 
top dry weight of 'Hershey's
Red' azalea in three pot/mulch combinations.
Root coverage (%) Relative 
root Growth Top 
dry
North South developmentz 
index, ('cm)
y  
weight (g)
Black pot/whi-te mulch 7.2 dx 0.7 d 2.6 b 23.6 b 27.5 b
White pot/black mulch 31.1 b 20.4 c 3.3 a 26.0 a 36.7 a
Black pot/plywood frame 47.4 a 42.6 a 3.6 a 25.8 a 34.1 ab
zl=1least developed 
and 5 = most 
developed root 
systems.
Growth index = (height t. idth)/2.
xMean separation 
within columns 
by Duncan's 
multiple range 
test, 5% level; 
root coverage
values separated among all means.
Literature Cited:
1. Cooper, A. 
J. 1973. Root temperature 
and plant growth.
Research Review 
No. 4. Commonwealth 
Bureau of Horticulture 
and Plant-
ation Crops. East 
Malling, Maidstone, 
Kent. 73 p.
2. Kramer, P. J. 1949. Plant 
and soil water relationships.
McGraw-Hill, New 
York. 341 p.
3. Rauch, F. D. 
1969. Root zone 
temperatures studied. 
Miss. Farm.
Res. 32:7.
4. Whitcomb, C. 
E. 1980. Effects 
of container and 
production bed
cover on root temperatures 
and plant growth. 
Res, Rept. P-803. 
Okla.
Agri. Exp. Sta. 
Oklahoma State Univ., 
Stillwater.
Phytotoxicity of Chrysanthemum to 
Sprays and Drenches of Dursban
M 
- A
Potential Control for Leafminer, Liriomyza 
trifolii (Burgess)
Kenneth C. Sanderson and Willis C. Martin, Jr.
Nature of Work: The serpentine 
leafminer, Liriomyza trifolii 
(Burgess)
is a serious pest that has prompted 
three industry conferences 
to
identify, discuss and, hopefully, 
solve outbreaks of this difficult 
to
control pest (3). An important 
aspect of leafminer control is 
the
availability of effective insecticides 
which can reduce these outbreaks.
Repeated applications of 
broad spectrum insecticides 
and associated
mortality of natural enemies 
and insecticidal resistance 
have resulted
in less than satisfactorily 
control with currently 
recommended insecti-
cides. The effective life of any insecticide has been estimated to be three
years (1). In the authors' experience, insecticidal 
control has only been
achieved in commercial practice by treating for both adults and larvae.
Growers have tested Dursban
M 
on adults and reported that resistance develops
rapidly. Shuster and Everett (4) found foliar sprays of Dursban' ineffective
in reducing leafmining damage. Parrella et al. (2) 
have documented the
effectiveness of Dursban" (chlorpyrifos trademarked as Durtban" by Dow
Chemical Co., Midland, MI) controlling third stage larvae of L. trifolii
but indicated that phytotoxicity trials on chrysanthemum were not available.
The present study was conducted to evaluate the phytotoxicity of Dursban'
sprays and drenches on chrysanthemum.
Two experiments involving 
the chrysanthemum cultivars 
'Bright Golden
Yellow Princess Anne', 'Loyalty', 'Spirit', 
'Sunlight' and 'Yellow Mandalay
were conducted during 1982, Rooted 
cuttings were planted December 16,
pinched December 29 and treated 
with Dursban" on January 18 
in Experiment
In Experiment 2, cuttings were tansplanted 
on January 29, pinched
February 12 and treated 
on February 25. 'Sunlight' 
plants were grown as
"spray" types with the center flower bud being removed at disbudding.
Other cultivars had the lateral 
buds removed. Appropriate photocontrol
for commercial flowering of chrysanthemum 
was employed in each experiment
with the plants receiving supplementary incandescent 
light from 10 p.m.
to 2 a.m. each night starting at transplanting 
and ending at pinching.
'Bright Golden Yellow Princess Anne' plants received one week less light-
ing than the other cultivars (lighting 
terminated 1 week before the pinch).
Two media were used: Pro-mix (Premier 
Brands, New York, NY) and a 1:1:1
(v/v/v) soil, sphagnum peat 
moss and perlite medium. 
Media were amended
with 6 oz. limestone and 1 
oz. superphosphate per cu. 
ft. Fertilization
consisted of weekly applications of liquid 
fertilizer 20-20-20 (20N-8.7P-
16.6K) at the rate of 2 lb. per 
100 gal. Treatments consisted of 
Dursban
m
7E applied at 3 rates as a drench (4 oz. per pot) and one 
rate as a
spray. Application 
rates were derived 
from the manufacturer's 
recommen-
dation for use of Dursban
TM 
on turf and a bracketing effect was used 
for
drenching rates. DuPont Spreader Sticker was 
added to the spray at the
rate of 1.3 oz. per 100 gal. 
Five pots served as an experimental 
unit
and treatments were applied in a randomized 
block design with 2 replications.
Data on date of flowering, plant 
height, plant spread and flower number
were recorded when two-thirds of the 
flowers were open. Data from both
from both experiments were combined for statistical 
analysis.
4
Results and Discussion: None of the treatments produced any visible
symptoms of injury on the cultivars tested. There were no differences
in flowering time due to Dursban
M 
treatment, however all cultivars
flowered in the following order:'check (no treatment), 5 oz./100 gal.
drench, 20 oz./100 gal. drench and 10 oz./100 gal. spray. Dursban
m
treatments did not affect the plant height of any of the cultivars
tested, however the 5 oz./100 gal. drench produced the tallest plants
and the 20 oz./100 gal. drench produced the shortest plants with most
cultivars. Differences in plant spread were not significant, however
the 5 oz./100 gal. usually produced plants with the greatest spread.
Drenches and a spray of Dursban
m 
significantly reduced the number of
flowers on 'Bright Golden Yellow Princess Anne' plants but did not affect
flower number on other cultivars (Table 1). Check 'Bright Golden Yellow
Princess Anne' plants produced more flowers than plants receiving the
5 oz./lO00 gal. drench, 20 oz./100 gal. drench 
and 10 oz./l00 gal. spray.
This work shows that Dursban
M 
can be used safely as a drench on certain
chrysanthemum cultivars for the control of soil insects. In other
unpublished work by the authors, Dursban
m
has been used as a medium drench
on orchids without visible phytotoxicity and has produced transient
chlorosis and a reduction in flower number when applied as a spray (5 oz./
100 gal.) to 'Sunny Mandalay' chrysanthemums. A granular formulation
of chlorpyrifos (Dursban'), Lorsban 15G, has received labeling for broad-
spectrum soil insect control on agronomic crops and should be tested
on chrysanthemums because of its versatility of application (5).
Table 1. Effect of Dursban" on the number of flowers
per plant produced by 4"chrysanthemum cultivars
Treatment Rate Cultivars
oz./100
gal. 
Yellow
BGY Princess Loyalty Spirit 
Sunlight Mandalay
Anne
Check - 3.5az 4.2a 5.3a 7.5a 4.2a
Dursban' drench 5 3.2b 4.4a 5.1a 7.0a 4.1a
Dursban"
M 
drench 10 3.4ab 4.6a 5.3a 7.4a 4.Oa
Dursban
m 
drench 20 3.3b 4.5a 5.5a 7.4a 4.la
Dursban
TM 
spray 10 3.3b 4.3a 5.1a 7.2a 4.Oa
ZMeans in columns followed by the same letter(s) are not significantly
different according to Duncan's multiple test at 5% level.
Literature Cited:
1. Keil, C. B. and M. P. Parrella. 1982. Liriom 
za trifolii
on chrysanthemums and celery. p. 162-167. In S.L . Poe (ed. Proc.
of the 3rd. Ann. Industry Confr. on the Leafminer. Soc. Amer. Flor.
Alexandria, VA.
2. Parella, M. P., K. L. Robb, and P. Morishita. 1982. Leaf-
miner on chrysanthemums - chemical controls. So. Flor. and Nurseryman.
January 29. p. 21-23.
3. Poe, S. L. 1982. Purpose of conference. p. 1-2. In S. L.
Poe (ed.) Proc. of the 3rd. Ann. Industry Confr. on the Leafminer.
Soc. Amer. Flor. Alexandria, VA.
4. Schuster, D. J. and P. H. Everett. 1982. Laboratory and field
evaluations of insecticides for control of Liriomyza spp. on tomatoes.
p. 20-30. In S. L. Poe (ed.) Proc. of the 3rd. Ann. Industry Confr.
on the Leafminer, Soc. Amer. Flor. Alexandria, VA.
5, Young, J, K, 1982. Proper application of Lorsban 15G insecti-
cide to control soil insects in corn. Down to Earth 38(2):6-8.
Cutting Propagation of Chionanthus retusus
(Lindl. & Paxt.), Chinese Fringetree
Fred B. Perry, Jr.
Nature of Work: The pure white flowering form of Chinese Fringetree has
been grown on a very limited scale for many years due to propagation
difficulties. Viable seed production is sparse and germination is poor
because of various internal dormancies (requiring a month of stratification
at 70
0
F followed by two months at 40oF). Even with proper stratification
procedures, germination may not occur until the second spring. Cutting
propagation of Chinese Fringetree has been also recognized as being very
difficult if not almost impossible.
On May 17, May 31, and June 14, 1982, 8-inch (20 cm) cuttings were
taken from suckering juvenile shoots on interior branches of 25-to-30-year
old stock tree plants. The shoot tips were not completely mature with
fully expanded leaves until the mid-June cutting date. Five to six
leaves remained on each cutting. Root-inducing treatments were check (none)
and talc preparations of IBA at 0.3% and 2.0%. The base of each cutting
was wounded by removing a thin strip of bark from two sides 3/4-inch (2 cm)
long and < 1/8-inch wide (2 mm). Cuttings were inserted under mist in a
medium of 1 sand:1 peat:l perlite and watered in with a Captan drench (1 lb.
per 100 gal.). The mist cycle was 2 seconds each 2 minutes during day-
light hours only. There were 30 cuttings per treatment in 4 replications.
The replications were represented by 1 = tips, terminal 8 inches,
6
2 = second cuttings, 3 = third cuttings, and 4 = base cuttings from
suckering shoots, Plot design was a complete randomized block for each
cutting date,
Results and Discussion: Rooting percentages 
increased with increased
concentrations of IBA up to 2%, with maturity date, 
and with the more
basal position on the shoot (Table 1). Poor or no rooting occurred on
cuttings with no rooting inducing treatment and on tip cuttings 
through-
out the study. Rooting response to 0.3% IBA increased 
with cuttings
taken down the stem and with increased maturity 
date; however, the best
average response of 26.75% is considered poor. 
Overall rooting response
to 0.8% IBA and 2.0% IBA also improved 
with more basal position taken and
with maturity and reached 52.50% and 56.75% respectively. 
The best root-
ing percentages were achieved on basal cuttings treated 
with 0.8% IBA
in May and June (87% & 90%) 
and with 2.0% IBA (97%).
These plants can be propagated by mature spring 
cuttings, and top
quality specimens can be grown. 
The results of this study show 
that the
maturity of the cutting is of prime importance, 
not so much from the
standpoint of a calendar date but from the standpoint 
of physiological
maturity. The optimum maturity 
of the cuttings is at the point 
when the
youngest terminal leaf has completely expanded and 
reached full size and
thickness. In central Alabama this can be May 
15 to June 15 depending on
the earliness or lateness of the season for 
a given year.
The best cuttings are taken from juvenile 
shoots arising low on the
stock plant. Shoots should be strong, thick, 
vigorous, current seasons
growth and 1/4-3/8 inch (5.1 cm) in diameter. 
Small diameter shoots taken
high in the plant have not rooted as 
rapidly or as well as the larger
stronger shoots. Such cuttings, if rooted, 
do not seem to grow off well.
Cuttings are made by sectioning these shoots 
into 6-to-8-inch (15-19 cm)
cuttings with three or more nodes remaining, discarding 
the weak small
diameter branch tip.
Cuttings should be taken in early morning when 
turgid and fully
protected against drying through 
every stage of preparation until 
in the
mist bench.
Table 1. Effect of propagation date, 
IBA, and type of cutting on rooting 
of
Chinese Fringetree Chiohanthus 
retusus (LindE & Paxt.)*
Percent rooted
Rep. I ROI-I -Reps.1-1 --
Re-p . I'V Av erage
Tip cuttjng 2nd. cutting 
3rd.*cutting Base cutting.
5/17 stuck
6/30 harvest
Check
0.3% IBA
0.8% !BA
2.0% 
,BA
5/31 stuck
7/14 harvest
Check
0.3% IBA
0,8% IBA
2.0% IBA
6/14 stuck
7/28 harvest
Check
0,3% IBA
0.8% IBA
2.0% IBA
0
0
0
3
0
0
0
30
0
7
43
50
00
0
0
10
57
53
0
0
7
57
0
7
53
70
3
40
63
77
0
0
0
0
5.7513
93
0
20
87
97,
0
57
90
97
45.00
0
8.50
45.75
54.25
0.75
26.75
52.50
56.75
Thi rty 8-inch cuttings were taken for each cutting type from suckering Juvenile
32-to' 38-inch shoots s5tarting at the shoot terminal 
or tip.
8
Effect of Growth Retardants on
English Ivy, Hedera helix L.
Kenneth C, Sanderson, Willis C. Martin
Jr., and Lih-Juy Shu
Nature of Work: Growth control of members 
of the Arailaceae is
desirable because of their widespread use in interior 
landscapes.
In previous work on Brassaia actinophylla Endl. (2) and 
Hedera helix
L. (1), a single spray application of w-Nine
M 
(daminozide or butanedioic
acid mono (2,2-dimethylhydrazide by Uniroyal Chemical, 
Bethany, CT) or
A-Rest
T 
(ancymidol) or a-cyclopropyl-a-.(pmethoxyphenyl)-5-pyrimidine-
methanol by Lilly Research Laboratories, Greenfield, 
IN) has caused some
reduction in pl.ant growth. Single spray applications 
of Stemtrol
TM
(piproctanylium bromide or 1-allyl-l-(3,7-dimethyloctyl)-piperidinium
bromide by Hoffman La Roche Inc., Nutley, 
N.J.) have been effective.
The objective of this research was to study 
the effect of 2 applications
of these retardants on the shoot length 
and plant dry weight of Hedera
helix L.
On June 23, two cuttings of English ivy were directly propagated
in 15-cm (5-in.) pots under mist (5 sec. out of every 100 sec. 8:00 
a.m.
to 5:00 p.m. daily). The pots contained 1:1:1 (v/v/v) soil, 
sphagnum
peat moss, and perlite medium amended with 60 g (2.3 oz.) dolomitic lime-
stone per cu. ft. Plants were grown in a lightly shaded greenhouse
equipped with fan and pad cooling (thermostat set at 21
0
C. (70
0
F.).
Upon rooting, the plants were fertilized weekly with water soluble
fertilizer 20-20-20 (20.0 N-8.7 P-16.6 K) at the rate of 908 
g (2 lb.)
per 378.5 liters (100 gal.). On August 2 and September 2, the 
growth
retardant treatments shown in Table 1 were applied to the plants. 
Sprays
were applied with a low-pressure, high-volume sprayer unti runoff.
For the drenches, 100 ml (3.3 oz.) were applied to each pot. Treatments
were applied in a complete randomized block design with 4 replications
and 4 subsamples (pots) per treatment. The height of each plant in each
pot was determined on August 2 (prior to treatment) and on October 31
(after the second treatment) and the increase in new growth was calculated
for analysis. For dry weight determinations, plants were severed at
the soil line and dried in an oven at 80
0
C. (176
0
F.) prior to weighing.
Results and Discussion. The greatest reduction in new growth occurred
on plants receiving 5,000 ppm N-Nine or 150 ppm A-Rest sprays (Table
1). Stemtrol
TM 
was ineffective as a spray or drench in reducing growth
of English ivy. Growth of plants receiving A-Rest
TM 
drench was less than
that of plants receiving no treatment or Stemtrol"
M 
sprays or drenches.
The effect of the retardants on plant dry weight was similar 
to their
effect on height. Plants receiving 150 ppm A-Rest'" sprays weighed 
the
least and differed in dry weight from check and Stemtrol
TM
treated plants.
Plants receiving A-Rest
T 
drenches did not differ in dry weight from
plants receiving A-Rest
t 
sprays or B-Nine
T 
sprays.
Our work shows that B-Nine
t 
sprays and A-Rest
T 
sprays can be used
to retard the growth of English ivy. Such growth retardation might be
useful in the production of hanging baskets and compact potted plants
and in the maintenance of plants in interior environments.
Literature Cited
1. Sanderson, K. C. and W. C. Martin, Jr. 1979. Growth retardant
effects of Stemtrol on selected plants. Proc. SNA Res. Confr. 24:205-
206.
2. Sanderson, K. C. and W. C.. Martin, Jr. 1983. Maintaining
the growth of Schefflera actinophylla Endl. with chemical inhibitors.
Proc. SNA.
10
Table.. .Effect of growth retardants on new growth and
dry weight of English Ivy-,Hedera-helix La
Treatment Rate New-growth Plant dry ht
(ppm) (cm)Z.(g)z
None 24.2a 8.6.ab
B-Nine spray 5,1000 .6'.9C 6.5cd
Sterntrol spray .150. 22.5a 9.3a
A-Rest spray .150 .8,,4c 5,6d
Stemtrol drench 250 24.3a I.5bc
A-Rest drench 2 .1437b 7.Ocd
z
Metric conversion: .2.5"cm = 1 inch,*28.4= 10 ounce.
YMeans in columns followed by..the- same letter(s) ".are not significantly different
according to Duncan's multiple range test at the 5% level.
R
t