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:
- 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:
- 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.
- 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:
- 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
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:
- 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 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.
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 (24-26°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.
- 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