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Poinsettia
Guidelines
P. Allen
Hammer
Poinsettia
production starts with planning and not
with panning. The first step in the
planning process is to determine when you
want plants salable. From that date, the
timing of every other process is
determined. It is real tempting to write
this from flowering to propagation,
however I will not do that to avoid
confusion.
Planning
(scheduling) Decisions
Flower date -
?
(response
group)
Short days start
- ?
Pinch date -
?
Pot date -
?
Propagation date
- ?
Stock and
Propagation
Poinsettia stock can
be planted in March for a 3 pinch program,
April for a 2 pinch program, or May for a
1 pinch program. Each of the programs have
advantages and disadvantages. Less
cuttings are produced per plant with the
later planting, however the saving of
early spring space for other production is
often more valuable. Single pinched stock
plants can also be grown in small
containers but certainly require more
greenhouse space. Stock plants should
receive adequate light and space for
pinching and harvesting of
cuttings.
Stock plants must be
grown in long days. Incandescent lighting
(10 foot candles) should be provided from
10 p.m. to 2 a.m. from planting until
mid-May. Plants are pinched 2 weeks after
potting and every 4-6 weeks to buildup
cuttings and to maintain soft vegetative
growth. 2-4 nodes are left on the pinched
shoot. Poinsettia cultivar does affect the
number of cuttings from a stock plant as
well as scheduling of pinching and cutting
removal. Seek guidelines for specific
cultivars and follow those guidelines.
Those guidelines are available from the
breeders and suppliers.
Poinsettia cuttings
2.5-3 inches long are snapped or cut from
stock plants with a sharp clean knife. The
knife should be disinfected between stock
plants. Cuttings should be taken in the
morning when plants are turgid and should
be placed in clean plastic bags or on
clean newspaper. Cuttings should be
treated with a rooting hormone to improve
rooting uniformity and speed, stuck
quickly, and not allowed to wilt. It is
not necessary or desirable to remove
leaves from the cuttings.
Poinsettia cuttings
can be rooted in peat pellets (Jiffy 7's,
Jiffy 9's), phenolic foam (Oasis),
rockwool, or root medium filled cells.
Cuttings can also be direct stuck in the
finish container but this method requires
a great deal of mist space. Whatever root
medium or method is selected, great care
should be taken to assure the medium is
free of disease at the start and remains
disease free through out
propagation.
Cuttings must be
rooted under intermittent mist. Mist is
applied from sunrise to sunset at a
frequency that keeps cutting leaves
uniformly moist. Mist frequency may start
with a mist cycle of 10 seconds every 4-6
minutes for the first 4 days. Mist
frequency is reduced every 4-5 days as
plants callous and root. After cuttings
are stuck, it is very important to arrange
leaves so cutting terminals (growing
points) are not covered.
Temperature is very
important during propagation. Minimum air
temperature should be 70ûF. Bottom heat
should maintain a root medium temperature
of 75-80ûF. Cuttings should show visible
roots in 21 days and be ready for potting
in 28 days. Cuttings should be fertilized
under mist beginning 14 days after
sticking.
Scheduling
Poinsettia
scheduling is required to provide top
quality plants to the ever lengthening
poinsettia market. The present market
requires flowering plants from as early as
the first week in November through the
Christmas season. It is impossible to
provide plants in prime condition without
scheduling. Growing temperature should not
be used to schedule poinsettias. Low
temperatures, less than 62ûF. night/70ûF
day, will delay flowering but will also
reduce bract size. High temperature,
greater than 65ûF night/80ûF day, will
speed flowering but reduces plant quality
and fades bract color. Cultivars can also
be selected for early or late flowering,
however your customer may complain if
cultivars are changed during the marketing
period. Therefore cultivar selection,
although useful in specific cases, can not
always be used to spread poinsettia
flowering.
Response
group (short days start until
flower)
8 - 10
weeks
Natural season
flower dates (Nov. 20 - Dec.
4)
2 weeks is a big
difference
What is flowering in
poinsettias? Anthesis or visible pollen on
the first cyathia should be used as your
guide to a salable poinsettia. Plants
without pollen will never develop to their
full potential in the post harvest
environment and plants held in the
greenhouse after anthesis, even at cool
temperatures, will show reduced
postharvest quality and
longevity.
With all the new
cultivars and their differences, along
with the need for prime plants over a four
week period, make poinsettia scheduling
much more difficult. Different growth
habits among cultivars also adds to the
complexity. And on top of this complexity
add the differences in growing conditions
between the northern and southern
production areas.
Cultivar
Growth
Habit
Short
Medium
Tall
But there are some
general guidelines that are very important
to remember: Natural short days start
around 25 September (probably a little
earlier for Freedom). If you do nothing,
flower initiation will occur on that date.
Lighting, to prevent initiation and make
sure the plants remain vegetative, should
start on September 5.
Lighting should
begin September 5.
Two to three weeks
of growth is needed between panning and
pinching to develop a good root system
before pinching. The time between pinching
and the start of short days is to me the
most critical decision on overall crop
quality. This can vary between two to five
weeks, depending on the cultivar and
growing conditions. I would strongly
suggest you seek information from the
breeders and universities in your specific
area to help in these scheduling issues.
The time between the pinch and the start
of short days greatly affects final height
and overall plant size. We have tools to
control size but few tools exist to
increase size after the start of short
days. The maximum potential height and
overall plant size is in some respects
determined at the start of short
days.
Freedom
scheduling as an example between
flowering time and
region1
North
South
early
late2 early
late2
pot Aug. 05 Aug.
15 Aug. 15 Aug. 21
pinch Aug. 19
Sept. 05 Sept. 1-7 Sept. 10
short days
natural Sept. 29 natural Oct.
06
flower Nov.
15-25 Dec. 01 Nov. 15-20 Dec.
01
1long day
lighting should start on Sept.
5
2from Nell,
Barrett, Hartley Grower Talks/August
1993.
Media and
Fertilization
The root medium used
for poinsettias should be porous,
well-drained, contain a moderate nutrient
content, have a pH of 5.8-6.2, be free of
insects and disease pests, and be easy to
manage. You also want to select a medium
that will be appropriate for the consumer.
It should not be so well drained that in
the home environment it is impossible to
keep it moist.
Poinsettias have
generally been considered a high fertility
requiring crop. Although the light leaf
cultivars fit into this category, the
newer dark leaf cultivars require lower
nutrient levels (150-200 ppm N). In fact,
high levels of fertility (300 ppm N) can
reduce crop quality in the darker leafed
cultivars. My experience would suggest
that you really need to fertilize the
light and dark leaf cultivars differently
and not compromise somewhere between the
high and low levels when growing both
groups in the same greenhouse.
Micro-nutrients are
important in poinsettia production.
Poinsettias have a high requirement for
molybdenum (Mo) which is generally added
at each watering at 0.1 ppm.
0.1 ppm Mo
Application
Stock
1 oz. of ammonium
or sodium molybdate/40.0 fl. oz.
water
Application
0.15 fl. oz. of
stock solution/100 gallons of
water
Research has also
shown the importance of the calcium to
magnesium ratio for adequate calcium
uptake in poinsettia production. High
levels of magnesium interfere with calcium
uptake, while too low levels of magnesium
will cause magnesium deficiency, another
common problem in poinsettia production.
The best ratio of Ca:Mg for poinsettia
production appears to be 2:1. Both calcium
and magnesium should be monitored with
root medium analysis because hey are both
very important macro nutrients in
poinsettia production.
Height
Control
Growers generally
apply a chemical growth retardant to
poinsettias to reduce height and tone the
plant. Commonly used chemicals are:
Ancymidol (A-Rest), Daminozide (B-Nine
SP), Paclobutrazol (Bonzi), Chlormequat
(Cycocel), (Sumagic), and B-Nine
SP/Cycocel tank mix. Different cultivars
respond differently to the various
chemicals therefore growers must adjust
rates in their own production. General
ranges are: Cycocel, 1,000 - 3,000 ppm;
Bonzi, 10-30 ppm; Sumagic, 2-10 ppm;
B-Nine Sp/Cycocel tank mix, 2500 ppm
B-Nine SP/1500 ppm Cycocel; and A-Rest,
.25 to .5 mg a.i. drench. Chemical growth
retardants should not be applied after the
start of short days as bract size can be
significantly reduced in the northern
United States.
Cut-off dates
for B-Nine/Cycocel, Bonzi,
Sumagic
North - start of
short day
South - 2-4 weeks
after start of short
days
Research has shown
that very low concentrations (1-2 ppm) of
Bonzi or A-Rest can be applied as a drench
as late as early November for height
control without a significant bract size
reduction. This approach is useful to
correct a height problem occurring late in
the production cycle and to avoid late
stretch.
Late drenches
of growth regulators
A-Rest
1 ppm drench (4
fl. oz./pot)
0.485 fl.
oz./gallon
2 ppm drench (4
fl. oz./pot)
0.970 fl.
oz./gallon
Bonzi
1 ppm drench (4
fl. oz./6" pot)
0.032 fl.
oz./gallon
2 ppm drench (4
fl. oz./6" pot)
0.064 fl.
oz./gallon
higher rates in
the South, lower in the
North
DIF is also used to
manipulate poinsettia height in those
areas with cool day temperatures. A
positive DIF increases stem elongation and
a negative DIF decreases stem elongation.
Computer software is available to use DIF
as a tool to control plant height. It is
very important that average daily
temperature not be changed when using DIF,
therefore both day and night temperatures
need to be adjusted to maintain the same
average daily temperature. Average growing
temperature can affect timing and bract
size.
DIF -
difference in day/night
temperature
Positive
DIF
warm day/cooler
night taller plants
Negative
DIF
cooler day/warmer
night shorter plants
Bract
Disorder
A number of bract
disorders can cause serious problems in
poinsettia production which appear
suddenly at flowering. The grower has
little chance to correct these problems
once they appear. Research has shown bract
necrosis (also called bract edge burn) can
be caused by a number of factors including
calcium deficiency in the bract tissue,
fluoride toxicity, imbalances in Ca/Mg or
Ca/K ratios, and pesticide toxicity. The
following guidelines can be used to help
reduce poinsettia bract
necrosis:
•
Supply adequate calcium in the
fertilization program.
•
Provide a calcium uptake
environment
- reduce
humidity in the
greenhouse
- maintain
good root growth
- use a
well drained root
medium
- reduce
fertilizer salts
•
Avoid fluoride
•
Avoid pesticides on
bracts
•
Maintain 2:1 calcium: Magnesium
ratio
•
Avoid excess levels of
potassium
•
Select cultivars less sensitive
to bract necrosis
Weekly sprays of 400
ppm calcium from calcium chloride
beginning at first color have
significantly reduced poinsettia bract
necrosis. Spray plants to runoff making
sure bract tissue is covered. I personally
do not recommend a wetting agent from fear
of phytotoxicity, although other
researchers do recommend a wetting agent
to improve coverage. Growers that have
experienced any bract necrosis should
spray plants with calcium as
insurance.
400 ppm
calcium spray solution
use
'reagent' grade chemical
Calcium Chloride
Dihydrate
(CaCl2 • 2
H2O)
1.47
gm/liter water
or
55.6 gm/10
gallons water
or
1.96 oz./10
gallons water
Post
Harvest
Poinsettia growers
have a responsibility in post production
longevity of the plants you grow. You
simply can not afford to just be happy to
have the plant out of the greenhouse door.
Happy poinsettia consumers make for repeat
customers.
The grower's
responsibility in postharvest care is to
provide the best poinsettia possible at
the proper stage of development, free of
insects and diseases, and low in soluble
salts (fertilizer). Research has clearly
shown that poinsettias have a much longer
and better display life when sold at
visible pollen. Young underdeveloped
bracts will never develop good color in
the postharvest environment. Pink bracts
on red cultivars result when plants leave
the production environment too early. Do
not sell a poinsettia before its
time!
Fertilizer salts
should be reduced before selling, however
t is not necessary or desirable to
completely eliminate fertilizer
application, just reduce the rate to 1/2
or 1/4 the rate used during early
production. Poinsettias can also receive
chilling injury when exposed to 50°F
or less for as short as a two hour period
of time. Chilling injury can cause
epinasty as well as leaf loss under the
most severe case. Transporting plants in
unheated trucks in the north and uncooled
trucks in the south can significantly
reduce poinsettia quality. Certainly a
general guideline is that poinsettias do
much better when placed in a uniform non
stressful environment. The best
environment could be compared to the
environment you would provide for a
newborn baby but just a few degrees cooler
(60 to 65°F).
The greenhouse
grower should provide the following
instructions to retailers. Upon receiving
plants, unpack and unsleeve them
immediately. Poinsettias left in the
sleeve become droopy. This epinasty is
caused by ethylene production from the
sleeving process. The longer poinsettias
are sleeved and the higher the temperature
above 65°F, the greater the
droopiness problem. The plants generally
recover from epinasty in a couple of days
when placed in a lighted area at
65-75°F if the sleeving period was
longer than a couple of days.
Poinsettias should
be placed in bright light at 60-65°F.
They should however not receive direct
sunlight under postharvest conditions. The
plants should be out of hot or cold
drafts. A heat duct or outside door should
not expose the plants to sudden changes in
temperature. At no time should poinsettias
be stored in a garage area.
Poinsettias are
fragile. Rough handling will bruise the
bracts and cause stem and leaf breakage.
Poinsettia plants can not be handled like
hard goods. Also be sure to provide
adequate spacing in the display area.
Plants should not be spaced so close
together that the bracts from one plant
rub against the bracts of an adjacent
plant.
As a poinsettia
producer and marketer, you can do a great
deal to maintain the potential postharvest
beauty and longevity built into the modern
poinsettia cultivars. At the same time you
can reduce the postharvest life of the
poinsettias you handle. It is extremely
important that we all do our very best to
give the consumer the best possible
poinsettia. Plant abuse anywhere in the
marketing chain will ultimately showup in
the final consumer setting - whether it be
a hotel lobby, mall display, or home
living room. I like the concept that each
poinsettia plant should be handled like it
is the one you would take home for
Christmas. Every poinsettia consumer
deserves such treatment.
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