Growers can increase the post-production longevity of their poinsettia crops by conditioning plants or “toning” them to become more durable. Other benefits of toning include a decreased incidence of production disorders such as bract edge burn, stem breakage and rapid loss of foliage and flower cyathia. While these problems may be more prevalent in specific regions of the country, no grower is safe from any one, or combination of these disorders. By adopting a philosophy of “toning” crops throughout production, growers can take the initiative to avoid these crop problems. Increased quality, profitability and consumer satisfaction should be the result of these efforts. Changes in cultural practices at particular stages of production are a way to accomplish toning.
As poinsettia crops enter the final stages of production, give special attention to cultural practices and greenhouse conditions that are appropriate for finishing the crops. The process of toning does not end until the plants have all been shipped.
Maintain normal temperatures (75-80°F/24-26°C day temperatures, 64-66°F/18-19°C night temperatures for most cultivars) throughout bract expansion and development. Higher day and night temperatures contribute to bract edge burn and premature cyathia drop. Until the plants have fully colored bracts (primary and secondary bracts), do not reduce temperatures on the crop. Avoid dropping temperatures below 58°F (14°C) after bract formation.
Maintain good ventilation and air circulation in the greenhouse to lower relative humidity to 90% or less. Bract edge burn can result from reduced root activity and restricted water uptake that occurs under conditions of high humidity. Conditions of high humidity favor Botrytis which can easily attack soft bract tissue during the final stages of development. Growers have found the use of horizontal airflow fans beneficial to enhance air movement, increase transpiration and even temperatures. Maintain good soil moisture management throughout the finishing stages of growth. Constantly wet soil will restrict root activity, increase the potential of root rot organisms, and result in softer plant tissue that is susceptible to damage.
Maintain full light intensities on the crop until primary bracts have fully colored and secondary bracts are near maturity. Any reduction of light before this stage will reduce bract color and slow development. Shading to 2000 foot-candles/21,520 lux after the bracts have matured prevents fading and potential damage from sunburn.
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