Energy Efficient Poinsettias
Energy costs are higher than ever before, further reducing an already shrinking profit
margin on poinsettia production. Cold temperature production offers growers the ability
to save energy and reduce costs associated with production and improve profitability! In
addition to reduced energy needs there are other benefits to producing poinsettias cold.
Additional benefits include:
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Enhanced bract color
Tighter bracts make beautiful retail displays
Enhanced cyathia retention
Plants withstand the rigors of handling and transportation better
Cold grow production does not simply mean turning the thermostat down. In order to
produce a quality crop it is imperative growers follow certain cultural guidelines and
choose from a list of varieties proven to perform well at colder environments. Crop
scheduling and variety selection will be the first important decision to make. The do's
and don'ts in the planning process include:
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Choose varieties well suited to cool temperature production
Choose early varieties. Colder finishing temperatures can cause a 1-3 week
delay in finishing times. Those varieties that initiate earlier and have shorter
response times will still finish within an acceptable amount of time to meet
market demand even when delayed.
Choose varieties with good vigor.
Schedule crops to plant and pinch 1-2 weeks earlier than normal. This added
grow time early in production will compensate for reduced vigor once
temperatures are dropped. It is also important for building strong root systems
and achieving adequate finished height.
DON'T
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Grow late varieties and those with smaller bracts under cooler temperatures.
Late varieties will simply finish too late. Bract expansion may be slightly reduced
with cold production. Reduction in bract size on a bract that is naturally small
already will be very noticeable.
Grow early and late varieties in the same greenhouses.
Grow compact varieties.
Recommended varieties for cold production include:
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Advent™ Red
Early Joy™ Red and Pink
Freedom™ Early Red, White, Pink, and Marble
Jester™ Red, White, Pink, Marble, and Jingle
Freedom™ Red, White, Pink, Marble, Salmon, Peppermint, and Jingle Bells
Prestige™ Early Red
Polar Bear
Autumn Red™
Red Velveteen™
Jubilee™ Red
Shimmer Surprise!™ and Shimmer Pink
Prestige Early Red Nov. 1st grown Cold
Prestige Early Red Nov.1st grown at
normal temperatures
Cultural Concerns:
Temperatures are not the only adjustment to culture that must be made using the cold
production technique. At cooler growing temperatures, the plant’s metabolism and
growth rate will slow, affecting nutrient and moisture uptake. Shoot growth and root
growth will be affected. Considerations and adjustments to culture for the roots and top
growth include:
For the roots:
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Avoid growing plants on the floor.
Maintain average root zone temperature at 65°F (17°C).
Irrigate late morning and finish by 12:00 noon and avoid further cooling of the
media with cold water applied early in the day. By finishing mid day the foliage
will still dry before nightfall.
Plants will be using less water; monitor soil moisture levels closely.
Less water uptake equals less nutrient uptake; monitor pH and EC closely to
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maintain acceptable levels for healthy growth.
A preventative fungicide program for root rotting pathogens is important with cool
temperature production as conditions will be more favorable for diseases such
as Pythium.
Check roots once or twice weekly and watch carefully for signs of stress or
disease.
For top growth:
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Modify early growth regulator applications to reflect the early start! However,
later in the season when slower growth results from cold temperatures, less
PGR will be required.
Cycocel alone early in the season will likely offer sufficient height control, but use
a good height tracking program, like On-Target, to monitor and react as needed!
Limit use of B-Nine only to the propagation phase. Products containing
Paclobutrazol are likely too strong and should be avoided with the cold grow
technique.
Colder night temperatures will result in a large positive DIF. Normally a positive
DIF environment encourages stem elongation, but research in developing the
cold production technique has shown excessive stem elongation is not a concern
due to the dramatic positive DIF.
Do not use an early morning negative DIF if growing with cold nights. Further
reduction in temperatures will delay flowering.
Reducing temperatures below 65°F (17°C) while plants are in the flower
development phase (late September and early October) decreases the rate of
development. Reducing temperatures too early will likely result in plants finishing
after the target finish date.
Provide good air circulation and adequate ventilation to reduce relative humidity.
Cold nights will increase moisture condensation in the canopy which can lead to
botrytis problems.
Preventative fungicide applications for Powdery Mildew and Botrytis are very
important!
Guidelines for cold production:
July and August- Add 1-2 weeks to traditional schedules to allow for strong growth
before temperatures are reduced.
August and September- Take advantage of long days and build strong plants with
fertilization, light, and spacing. Average daily temperatures of 66-68°F (18-20°C) will
prohibit early flower initiation. Though tempting, do not drop temperatures below 65°F
(17°C) during this time.
October- After flower initiation reduce temperatures to no less than 60°F (15°C). The
plants are still actively growing; reducing temperatures too fast will impact plant size
and timing.
November- Drop night temperatures to 55- 60°F (12-16°C). Do not drop temperatures
below 55°F (12°C). Flower development will not progress below 50°F (10°C) and
chilling injury may occur. On sunny days allow the greenhouse to warm to 75-80°F (2426°C) to offset cold nights. On cloudy days maintain 75°F (24°C). The goal is to
achieve an average daily temperature of 65°F(18°C).
Mid November to December- Plants are mature and ready to ship. Temperatures can
be dropped further providing the air in the greenhouse is dry and soil moisture levels
are monitored closely.
Additional Concerns:
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Remember that weather conditions change with each season. Adjust culture for
more than just cold temperatures as necessary.
The cold grow technique is very different than traditional poinsettia culture – trial
carefully! If plant health declines, bracts are too small, or color is delayed too
much temperatures should be increased!
Many growers are using Fascination (cytokinin/gibberellic acid) for rapid bract
expansion and stem elongation. While there is potential use for Fascination to
overcome small bracts from excessively cold temperatures this technique is still
experimental and applications should be trialed very carefully!
Weekly photos of flower progression and good record keeping will prove very
useful when evaluating the crop and making adaptations for future crops.
When interpreting height tracking graphs growers should expect earlier height
against the standard curve and less height later in the production cycle.
© 2011 Ecke Ranch