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) W-(0o Fertilizer Rate For Potted Calla Lily Production
R. T. Poole1 and B. Tjia2
Central Science University of Florida, IFAS
Library Central Florida Research and Education Center Apopka
CFREC-Apopka Research Report, RH-88-10
MAR 9 198m
U Since retailers and consumers are always looking for something
Universit)afWDOf O, the colored calla lilies Zantedeschia rehmannii are gaining
favor as a pot plant therefore research was done regarding the optimum
growing conditions for these plants as a flowering pot crop. This study
was undertaken to determine fertilizer rate effects on calla lilies, and to
subsequently determine the optimum fertilizer rate for the crop as a
flowering pot plant.
Materials and Methods
Experiment 1. Calla lily tubers, cultivars 'Black Magic' and 'Golden
Supreme, were obtained November 25, 1986. All tubers were soaked for 30
minutes in a 50 ppm solution of Pro-Gibb (GA,) to stimulate flowering then
randomly planted 1 tuber/6" pot containing Vergro container mix (Verlite
Co., Tampa, FL). Pots were placed in a glasshouse with a light intensity
of 1500 foot-candles maximum and watered 1-2 times/week. Temperatures were
65 900F. Pots were fertilized November 26, 1986 using Osmocote 19-6-12
at 10 rates starting with 2.4 g/6" pot/3 months and increasing in 2.4 g
increments to 24 g/pot/3 months (2.4, 4.8, 7.2, 9.6, 12.0, 14.4, 16.8,
19.2, 21.6, and 24 g). Treatments were replicated 6 times for Black Magic
and 5 times for Golden Supreme. After 2 weeks, pots were drenched with an
8 ml/l solution of Bonzi at 120 ml/6" pot (equivalent to 4 mg Bonzi/pot).
Using the pour-through method (1), soluble salts and pH measurements were
taken 3 weeks after initial fertilization and two more times at 4 week
intervals. Flower number was recorded throughout the experiment.
Eighteen weeks after potting, water was withheld and 2 weeks later,
tuber weight was taken and the experiment was terminated.
Experiment 2. A second experiment, using the tubers from experiment
1, was sE~arEe June 17, 1987. The tubers were planted in 6" pots
containing Vergro container mix (6 replications for Black Magic and 5
replications for Golden Supreme). Bonzi (4 mg/pot) was applied July 7,
1987. On July 8, all pots were fertilized using Osmocote 19-6-12/6" pot/3
months at the same rate for each tuber as it had in the first experiment.
Once initial growth was observed, pots were placed in 30% shade, with 9000
*Professor of Physiology, Central Florida Research and Education Center -
2Apopka, 2807 Binion Road, Apopka, FL.
Associate Professor, Ornamental Horticulture, University of Florida,
ft-candles maximum light intensity, and ambient temperatures of 75 900F.
Pots were watered twice weekly, more if deemed necessary to prevent
excessive drying out.
Initial height measurements were taken at 8 weeks, and at 12 weeks
height and number of shoots/pot were obtained. Plant quality was judged
November'17, 1987 and watering ceased. Tuber weights were taken December
29, 1987 and the experiment was terminated.
Experiment 3. Tubers of calla lily 'Pink Persuasion' were treated"
SeptemibeF10, 1987 with 50 ppm GA, (Pro-Gibb) as in Experiment 1. Tubers
were then sorted according to size for treatment uniformity. Tubers were
planted in 6" pots containing Vergro container mix and fertilized September
23, 1987 at the rates used in both previous experiments. The pots were
immediately placed in 30% shade, with 9000 ft-candles maximum light
intensity, and ambient temperatures of 75 90F. Flowering data were
taken on a continuing basis from first flowering October 18 through
December 30, 1987. Pots were then allowed to dry and tuber weights were
determined February 26, 1988.
In Experiment 1 soluble salts (Figure 1) increased for Black Magic and
Golden Supreme as the fertilizer rate increased. The pil of the soil
decreased as fertilizer rate increased. The pil Feb. 13, 1987 for the low
rate was 5.6, and 4.3 for the high rate.
SOLUBLE SALTS OF POTS
CONTAINING GOLDEN SUPREME
8 n br t
0 1.4 4.6 7,3 t. 12 14.4 1e.6 19.2 21.6 24
a ----- --- 'fi---*'-- .. .-~-. '---~~~. -.
g 19-0-12/6' pot applied Nov 26, 1986
Effects of fertilizer rate on flower number was found to be
significant only with Golden Supreme variety in which the number of flowers
decreased with an increase in fertilizer. (Figure 2).
CALLA LILY FLOWERING
AT INCREMENTAL FERTILIZER RATES
Flower Number/a" pot
S1 -4- Black Magl -*- Golden Supreme -11- Pink Persuaulon
I| ..... I ,I,1 ,1 .I .1._........ I J J --.. ... .- 1.. .
0 2.4 4.8 7.2 0.6 12 14.4 1.8 10.2 21. 24
Fertilizer Rate (g 19-6-12/3 mos)
Tuber weight decreased significantly with an increase in fertilizer
rate in both Black Magic and Golden Supreme, but tuber weight of Pink
Persuasion was not affected. (Figure 3).
CALLA LILY TUBER WEIGHTS
AT INCREMENTAL FERTILIZER RATES
Sok Magle olden Supreme Pink Pru lo
2 I .. ... .... t _... ..... .. I ... i ... .. . ..... ..
0 2.4 4.0 T.2 0.0 12 14.4 18.8 19.2 21.0 24
Fertilizer Rate (g 19-6-12/3 moo)
Plant quality of Black Magic and Golden Supreme increased with
Preliminary research on these varieties of calla lilies would suggest
that a fertilizer level of approximately 5 g (19-6-12/3 mo)/6" pot would be
~~,a .~ ;;;;;7~.*-rrii~~l~*iri~~;-li -i (Ini~ii~.~i\l-l~--n~
I optimum for 'Black Magic' and 'Golden Supreme', but Pink Persuasion
tolerated a wide range of fertilizer levels.
Flower number and tuber weight (a possible indication of future flower
number) would be extremely important parameters for choosing a satisfactory
flowering pot plant. Plant quality is generally a judgement of a plant's
size and flower color and not related to flowering capabilities. Therefore
when selecting a fertilizer application rate for the potted flowering calla
lily, one might be well-advised to use the lower rate of fertilizer. This
could reduce both production costs and possible ground water contamination
caused by run-off.
1. Wright, R. D. 1986. The pour-through nutrient extraction procedure.
~; .rpu~F~u~t~,Ylnrr~~! rl-c~Ulyii~-i