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The
Poinsettia
 |
Jay
B. Fitzgerald, Extension Horticulturist
Donald H. Steinegger, Extension Horticulturist
Growing
poinsettias so that they re-bloom is easier if you understand
and
follow some basic horticultural and pest management procedures.
Poinsettias are
the most popular decorative plants for the Christmas and New
Year holiday seasons. The newer cultivars often remain
colorful until spring and do not have to be discarded when
they finish blooming. Following a few basic principles can
bring the plants back into full bloom. |
Ideal
Temperatures
To prolong a poinsettia's blooming
period, place the plant where it will receive a maximum amount of
indoor sunlight. Avoid drafts that cause rapid temperature
fluctuations and premature leaf drop. Night temperatures should be
no cooler than 600F to 650F. Day temperatures
should not exceed 800F. Poinsettias will experience
premature leaf drop at temperatures below 550F.
Watering
Keep the soil slightly moist but not
soggy. When you get a poinsettia, check to see that the soil drains
adequately. About two weeks after acquiring the plant fertilize it
with a complete fertilizer according to package directions. Repeat
every seven to ten days until the plant loses its brightly colored
bracts. Water thoroughly and allow water to drain through the
container.
Plastic
Coverings
Often poinsettias are sold in a paper
or plastic sleeve, but they should not remain sleeved any longer
than necessary. Ethylene gas can accumulate within the sleeve and
cause premature flower drop and leaf curling. Leaf drop is a common
malady in poinsettias.
Disease
and Insect Pests
Several insects may attack
poinsettias: white flies, fungus gnats, mealybugs, and spider mites.
But the most serious diseases that affect poinsettias are soilborne
and are primarily fungi. The easiest methods for controlling these
disease organisms are by sanitation and periodic soil drenches with
a recommended fungicide.
Reflowering
Many of the new
poinsettia cultivars will keep their leaves and remain
attractive even in summer. If the plant retains its leaves,
treat it like any houseplant. Place it in a sunny location
apply a complete fertilizer containing trace elements once
every two weeks. As soon as night temperatures reach a minimum
of 600F, the can be set outside.
If a poinsettia plant drops its leaves or is no longer
attractive let the soil dry out and keep the plant in a cool
location such as basement window ledge; it still needs some
light. The temperature should not rise above 600F
with about 500F to 550F being best.
Bring the plant out of its resting stage in late April or
early May and cut the stems back to about 3 to 5 inches above
the soil. If there is more than one plant per pot, separate
them and replant in individual containers. |
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If repotting is necessary, use a soil
mix that is loose, porous, and well drained. Use a soil mixture
composed of three parts garden loam, two parts organic matter (peat,
compost, and leaf mold) and one part perlite or vermiculite. This
mixture should be pasteurized at or about 1800F for 30
minutes. You also can buy a premixed, pasteurized media. If you are
mixing your own soil, add one teaspoon of superphosphate or bone
meal for every 2 1/2 cups of soil mixture and thoroughly mix in.
After repotting, thoroughly water the
plant with a fungicide solution to prevent disease infestation.
Place the plant in a light, warm place and water whenever the soil
begins to dry. As soon as the night temperature reaches a minimum of
600F, the plant can be set outside. Place the plant in a
shady location for two to three weeks to allow for acclimatization
and to prevent leaf sun scald, then sink the pot in a sunny location
with well-drained soil. Give the pot 1/4 turn every few weeks to
break off any roots that might be growing through the drainage
holes.
Once the new shoots are about 1 inch
long, apply a complete fertilizer containing trace elements.
Water-soluble fertilizers are easiest to use. Slow release
fertilizer also may be successfully used - follow label directions.
Fertilize plants at seven to ten day intervals. To prevent your
poinsettia from getting to tall, pinch off or prune the growing tips
when they are about 4-6 inches long. If the new shoots grow another
5 inches before late August, repeat the process. Pruning shapes the
plant to form an attractive compact growth.
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When night
temperatures become cool, 550F - 600F
bring the plant indoors to a sunny location. Beginning Sept.
25, poinsettias need complete darkness from 5 p.m. to 8 a.m.
daily. Put a cardboard box or other device over the plant to
provide the "short day". Lights from any lamps will
prevent normal flowering of an uncovered plant. Continue this
"short day" treatment until the plant bracts show
color in late November. Short days and 600F - 650F
night temperatures are essential for good bract development. |
Poinsettias bloom according to day
length. Varieties are grouped according to the amount of time
between short days and the appearance of colored bracts. Cultivars
such as Amy and Lady will bloom about eight weeks after the onset of
short days. Jingle Bells and V-14 Glory will bloom about 100 - 11
weeks after the onset of short days. Other cultivars may respond
differently
Propagation
If plants get too tall and you want
to propagate them, take leafy cuttings during early to mid-August.
Cuttings should be about 4 inches long and may be rooted in any
pasteurized media. The use of rooting compounds will increase the
percentage of cuttings that will root and the rate of rooting. Place
the pots where humidity is high. A terrarium or similar structure
with high humidity is an ideal location for raising poinsettias. The
leaves on the cuttings should not wilt. To prevent this, reduce the
amount of leafy surface by cutting some basal leaves in half -
shading the cuttings. The more light the cuttings can be exposed to
without wilting, the more rapidly the rooting and the more vigorous
the rooted cutting. Keep the medium moist but not saturated with
water. Air temperature of about 700F by day and 600F
by night is best for rooting. Cuttings will root in about three to
four weeks. Further treatment of the rooted cuttings is the same as
for plants bought from commercial sources.
From and article
published by Cooperative Extension, Institute of Agriculture and
Natural Resources, University of Nebraska-Lincoln
File under: Horticulture
A-40, Ornamentals
Issued January 1992, 3,000
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