SEPTEMBER 1958
SUPPLEMENTARY ILLUMINATION
of POINSETTIAS
TOK FURUTA, Associate Horticulturist
THE poinsettia, Euphorbia pulcher-
rima, along with holly, symbolizes
Christmas. It normally blooms during
the first part of December and begins
to decline in quality by Christmas.
Native to moist shady parts of tropi-
cal Mexico and Central America, poin-
settias are valued for the showy bracts
that comprise part of the "flower." The
actual flowers are small, round struc-
tures, usually green, located in the
center of a cluster of colored bracts.
Many varieties are available. 
Those
most commonly used have red bracts.
Varieties with white and pink bracts
are gaining in popularity. Those with
white bracts have better lasting quali-
ties than the red. Either single or dou-
ble bract varieties are available.
Time of flowering can be controlled
by temperature control and pinching.
However, presence of Thielaviopsis root
rot and the natural difficulty of regulat-
ing fall temperatures in the South have
made this approach difficult. Also,
many people prefer plants that have
not been pinched.
Since poinsettia flowers develop dur-
ing short days, control of day length
presents a method of timing the flowers
for Christmas. Experiments were con-
ducted at the Agricultural Experiment
Station of the Alabama Polytechnic In-
stitute from 1951 through 1956 to study
this method.
MATERIALS and METHODS
All plants used 
in these experiments
were propagated by using stem cuttings
4 to 6 inches long taken in August and
September. All stock plants came from
California and were grown outdoors in
full sunlight.
Cuttings were dipped immediately
after taken in cold water to stop the
flow of latex. Prior to inserting in the
propagation medium, the base of the
cutting was dipped in ferbam or a mix-
ture of ferbam and a commercial root-
ing powder.
Rooted cuttings were 
potted at first
in 21/2 or 3-inch pots. Later three of
these plants were placed in a 6-inch
pan. The night temperature was main-
tained at a minimum of 600 F. Recom-
mended commercial cultural practices
were followed.
Varieties used for these experiments
AGRICULTURAL EXPERIMENT STATION
ej 1o ALABAMA POLYTECHNIC INSTITUTE
LEAFLET 58
E. V. Smith, Director
Auburn, Alabama
were: Indianapolis Red, Oak Leaf, Im-
proved Albert Ecke, Albert Ecke, Bar-
bara Ecke Supreme, Double Henrietta
Ecke, Ecke White, and Ecke Pink.
DATE of BUDDING UNDER
NATURAL CONDITIONS
The date of normal flower bud ini-
tiation is between September 20 and
October 1 at Auburn. This date is
important in using supplementary il-
lumination. Maximum efficiency was
achieved only when light was used
before initiation began. Lighting after
that date resulted in deformed flowers.
DATE of LIGHTING
Tests were conducted using the Albert
Ecke variety to determine what influ-
ence the first lighting date had on flow-
ering. Growing plants during long days
from October 1 or later resulted in de-
formed flowers. The main axis of the
stem terminated in a flower surrounded
by three normal leaves, i.e. a whorl of
three leaves, rather than the normal
alternate arrangement. A stem devel-
oped from the axil of each leaf of the
whorl. These in turn were terminated
by a normal poinsettia flower, with
bracts and flowers arranged normally.
Lighting plants after October 1 re-
sulted in delayed flowering, but caused
deformity. This deformity was objec-
tionable. When light was used before
September 20, this abnormal condition
did not develop.
DURATION of LIGHTING
Since light is used only to produce
a better quality plant for Christmas
sale, the length of lighting must be ac-
curately controlled. Too long a lighting
period results in a flower that is too
"green" to 
sell at Christmas. 
On the
other hand, too short a lighting period
produces a flower that is too "ripe." Re-
sults of experiments show that the night
temperature used will determine the
duration of lights. Plants grown at 600
F. night temperature with lights used
from September 15 to October 5-10
produced perfect flowers for Christmas.
The highest quality flowers at Christ-
mas were produced when the night
temperature was 650 F. and lights were
used from September 15 to October
10-15.
DATE of TAKING CUTTINGS
The date of taking cuttings had little
influence on the use of lights. Results
of experiments show that highest qual-
ity is produced when plants are potted
in soil by September 15 and lights
used. Cuttings made after September
15 were grown in a propagation bench
and lights used. However, this delay
was only a few days. The use of lights
on stock plants for cuttings to. be made
in October reduced quality. Plants from
October cuttings usually bloom just
before Christmas.
DAILY ILLUMINATION and
LIGHT INTENSITY
Supplementary illumination was used
from sundown to 10 p.m. or from mid-
night to 1 a.m. with equal results.
There was a relationship between the
time night lights were on and the in-
tensity of light. A minimum of 4 foot-
candles of light intensity was required
from midnight to 1 a.m. to efficiently
delay flowering but 2 footcandles was
sufficient for early evening lighting.
Weaker light delayed flowering but not
as much as higher intensities.
SUMMARY and
RECOMMENDATIONS
1. The normal date of flower bud
initiation on poinsettias at Auburn is
between September 20 and October 1.
2. The use of supplementary illumi
nation resulted in better quality plants
and flowers at Christmas,.
3. Using lights on plants growing
in soil by September 15 or plants
propagated before October 1 produced
better quality plants and flowers at
Christmas.
4. Highest quality at Christmas re-
sulted from using lights from Septem-
ber 15 to October 5-10 if the crop was
grown at 60' F. and to October 10-15
if grown at 650 F.
5. Delay in beginning the lighting
period until after October 1 resulted
in deformed flowers.
6. Lighting could either be done
from sundown to 10 p.m. or from mid-
night to 1 a.m.
7. Low light intensities were needed.
For lighting from sundown to 10 p.m.,
2 footcandles were sufficient, whereas
a minimum of 4 footcandles was nec-
essary for lighting from midnight to
1 a.m.