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S 10 Heat Tolerance of Dracaena 'Janet Craig' and Dr caena Ai maion
R. T. Poole and C. A. Conover
University of Florida, IFAS
Central Florida Research and Education Center Apia14: 1987
CFREC-Apopka Research Report, RH- 7-10
University of Florida
Dracaena deremensis 'Janet Craig' and Warneckii' are popular house-
plants adapted to low light locations. D. 'Warneckii' has attractive sword
shaped green and white streaked leaves whTile D. 'Janet Craig' has similar
shaped leaves which are dark green. D. 'Warneckii' sometimes has
serrations at the base of the leaves that appear as if someone had taken a
sharp knife and cut perpendicularly into the leaf margin. Sometimes cuts
are as much as one half the width of the leaf. D. 'Janet Craig'
occasionally develops chlorotic leaves in the vase which detract from the
appearance of the plant. Four experiments were conducted to
determine the cause of these problems.
Experiment 1. Rooted tips were obtained, planted in 6" tubs containing
Florida sedge peat:builder's sand (3:1 by volume), amended with 7 pounds
dolomite and 1-1/2 pounds MicroMax (a micronutrient blend from Sierra
Chemical Co., Milpitas, CA), and grown in a greenhouse with 1500 ft-c
maximum light. Five grams/pot of Osmocote 19-6-12 was applied*at 3 months'
intervals. Thermostats were set so that ventilation fans were activated in
each of the 4 sections in the greenhouse at 90, 95, 100 or 105F. Plants
were irrigated either 2, 4 or 6 times per week. The
experiment was initiated July 19, 1985. There were 6 replications.
There was a clear demarcation between plants in the section maintained
at a maximum of 90F and those maintained at 95-105'F (Table 1). D.
'Warneckii' grown at 90F had almost no notching, and D. 'Janet Craig' had
almost no chlorosis. Irrigation frequency did not affect chlorosis or
Experiment 2. A second experiment was initiated October 18, 1985.
Cultural conditions were similar except that maximum light was 1200 ft-c
maximum temperature, 90F and pots were irrigated twice weekly. Ca(OH)2
was applied to pots at levels of 0, 0.2, 0.4, 0.6, 0.8, or 1.0 grams in 200
ml water. When plants were examined December 17, 1985 no differences due
to treatment were observed.
Experiment 3. A third experiment involved weekly applications of iron, 0,
1 or 2 mg iron from iron sequestrene 330, to the vase of D. 'Janet Craig'
or 0, 2.5 or 5.0 mg boron from Solubor applied to the vase of D.
'Warneckii'. Trettme~Its were initiated August 23, 1985 and W'N4t'Wted
October 17, 1985. Treatments had no effect.
Experiment 4. This experiment was a repeat of Experiment 1 except that
irrigation was not a factor. Once again there was a clear difference
between 90 maximum and 95 105*F. The experiment was initiated June 26,
Professor of Physiology and Professor and Center Director, respectively,
Central Florida Research and Education Center, 2807 Binion Road, Apopka,
1986 and terminated September 16, 1986.
Summary. When growing Dracaena deremensis 'Janet Craig' or
'Warneckii', temperatures should be kept at 900F or below. If
temperatures cannot be controlled by fan and pads, increasing
shade or air movement might be beneficial.
Table 1. Influence of temperature and
Dracaena 'Janet Craig' and notching
irrigation on chlorosis of
of Dracaena 'Warneckii'.
Janet Craig Warneckii
temp. 'F 8 Aug 4 Sept 14 Aug 4 Sept
90 1.0 1.3 1.1 1.9
95 1.9 2.2 3.3 3.3
100 2.9 3.1 3.0 4.2
105 2.2 2.4 2.7 3.4
Linear 64.65** 61.25** 12.89** 23.45**
Quadratic 42.47** 40.96** 20.27** 18.37**
Cubic 9.09** 8.21** 3.71ns 0.83ns
2 1.9 2.4 2.6 3.1
4 2.1 2.2 2.3 3.5
6 1.9 2.1 2.7 3.1
Linear 0.02ns 3.03ns 0.06ns 0.04ns
Quadratic 3.34ns 0.00ns 1.23ns 2.17ns
z1 = none, 5 = severe
1 = none, 5 = severe
(ns) or significant at imr 1% (**)