Energy efficient poinsettia crops

January 17, 2008
Written by Jack Williams
12It’s that time again! The poinsettia season is upon us and with the crop comes the age-old challenge of how to maximize profitability in an environment of increasing costs and continued price pressure? This challenge is certainly not new to growers, but some of the potential solutions that break from traditional crop culture are!

When evaluating costs associated with poinsettia production, it is easy to identify those elements that contribute to cost of production (COP). Materials required, such as pots, soil, fertilizers and chemicals, make up a small portion of the total ‘per unit’ cost when spread across the entire production budget. While it seems pesticides and plant growth regulators are expensive to purchase and use, it is important to look at the allocated cost – when done, the contribution to COP is not significant.

Certainly it helps to use the least amount of chemicals possible, but at this point it is not reasonable to assume they will not be required. Growers need to focus on managing material costs by working with distributors to ensure the highest qual-ity products available are being obtained at reasonable prices.

When it comes to cuttings, remember the old adage ‘you get what you pay for!’ Suppliers have had to work hard to maintain competitive prices, so it is unlikely much can be done to reduce this input cost. Every year, we hear about cheap cuttings in the market; however, often the quality of these cuttings is less than ideal. Be sure to purchase cuttings from suppliers who provide consistently clean and healthy young plants. Lack of uniformity and poor quality cost more in the long run due to the additional work required in production. This is one area where compromising on quality is not a good idea.

However, it is the other inputs that provide a greater opportunity to reduce COP without compromising the quality of the finished plants. The two most significant costs associated with production are labour and energy. Managing these costs will do more to increase profitability than all the other costs combined.

Labour efficiency should focus on minimizing how many times the crop is handled. Every time the crop is touched costs money! This is a good example of where cutting quality has a distinct impact on costs. By starting with uniform, quality cuttings, growers require less sorting, grading and adjustment while transplanting, spacing, and ultimately packing the crop. Uniformity of cuttings also influences irrigation, plant growth regulator applications, and other activities where variation in plant size requires additional time and effort to compensate for when making these applications.

Having non-uniform plants on the same irrigation system results in losses due to over-watering plants that are not using water/fertilizer at the same rate as larger, more actively growing plants, OR under-watering plants, which can result in root system injury from salts accumulation in dry media. Either way, the result is a decrease in quality and increased losses. The bottom line in managing labour costs is doing what is required when required, and avoiding unnecessary work that does not yield higher value. Do things right the first time!

Energy has certainly been the topic of discussion given rising fuel costs. It is possible to grow poinsettias with less energy (cool temperatures) with good results using varieties adaptable to such programs. However, not all varieties are tolerant of cold temperature growing! Desirable characteristics associated with cold temperature tolerance include:

• Varieties with early season timing, although this is not an absolute for success. Using early blooming varieties reduces the risk of missing peak sales because developing bract colour and expansion happen earlier in the season when light levels and temperatures are not as compromised. This is especially important for growers in the northern regions, such as Canada, where day length and light intensities can drop significantly at the time bracts are developing.

• Varieties that are not genetically compact. Cool temperatures reduce the rate of growth and naturally compact poinsettias may not achieve the desired finished height specifications.

• Varieties with large bracts. Cool finishing temperatures do not encourage bract expansion, so varieties with naturally large bracts still expand enough to meet commercial quality standards.

• Varieties with a strong root systems; susceptibility to diseases like pythium or injury from salts in the media are more significant in cool, wet substrates.

Finished plants grown cool generally develop a more horizontal bract and leaf position because bracts do not expand as fully or become as soft as when grown at more traditional temperatures. Varieties that have a naturally cascading bract position benefit from this response, helping create an appearance of being fresh rather than tired and droopy. The colour intensity of bracts is also enhanced, especially red varieties.

For best results it is important to manage crop temperatures at key stages of development in order to keep plants on schedule. Considerations include:

• Start the crop early enough to achieve a good height and size; late transplanting does not yield quality results! Generally one to two weeks are added to the production schedule depending on the product form and required finished height. Advancing both the transplant and pinch dates ensures adequate vegetative growth develops while temperatures and rate of growth are favourable. If the crop is started late for any reason, it is unlikely to develop into good quality finished plants as a result of the slower growth rates at cool temperatures. If faced with this situation, opt to use a more traditional temperature regime for production.

• During initial development in long day conditions, build plants up through fertilization and optimum light and crop spacing. During September, an average 68ºF/18ºC is needed to keep the crop growing. Do not cut back on energy even though it is tempting to avoid heating at this time.

• Starting after flower initiation (late September to early October for most growers), reduce the average temperatures to no less than 65ºF/17ºC. This is the period of active growth for the crop, and cooling more than this can have more significant impact on height and size of the plants along with flower timing.

• Once colour has started to form in November, temperatures can be taken down another degree to average 63ºF/16ºC. Although bract size is compromised by these conditions, the varieties produced have large bracts naturally so the resulting size will still be acceptable.

• When plants have reached full maturity and are ready to be shipped to market, temperatures can be further cooled provided the greenhouse can be kept dry to avoid diseases like botrytis. Use of horizontal air flow fans in the greenhouse is highly recommended to keep moisture from forming on bracts and leaves. At these temperatures, be sure to manage irrigation and prevent soil from staying saturated; this condition can lead to pythium or other root rots.

It is important to separate varieties being grown cool from late blooming varieties to avoid delaying bract development of these poinsettias. The energy required to force them into bloom will negate any benefits of having grown the crop cool! During 2005, studies were conducted in the U.K. to evaluate if poinsettias started late could be bloomed successfully through managed temperatures and light. The initial results of this study concluded that energy costs associated with forcing poinsettias in this way were as much as three times greater than normal! When you consider the energy load required to force plants if behind schedule in November, it is easy to understand the cost far exceeds any savings gained from withholding energy earlier in the crop. Don’t get into this bind!

With good planning and close attention to the crop, it is possible to produce high quality blooming poinsettias with as much as 25 per cent less energy than traditional growing regimes require.

Are these concepts just crafty marketing programs targeted to keep growers producing the crop?

Not at all! Studies have been conducted during the past four to five years throughout some of Europe’s crop research stations and also by breeders, such as Ecke, to ensure culture and variety responses are well understood, making it possible for commercial growers to be successful. Evaluate if taking advantage of energy efficient production programs can be implemented to help reduce cost of production and increase profitability of the poinsettia crop in your greenhouses. You will be glad you did!
Varieties from Ecke proven adaptable for energy efficient (cool temperature production) programs include:
• Freedom series
• Freedom Early Red
• Autumn Red
• Red Velveteen
• Advent Red
• Prestige Early Red
• Jester series

Be sure to check with your supplier for suggestions on which varieties from other breeders are adaptable to a cold temperature,
energy-efficient production regime.

KEY POINTS
• When growing with less energy, monitor roots throughout production to avoid getting into problems with pythium or other disorders that result when the soil stays cooler and does not dry out as quickly.

• For best results, temperatures must be managed appropriate to the stage of development in order to support plant growth and flowering on time for the required sale dates and height specifications. It is also important to group varieties for energy efficient production together in order to avoid delaying the flowering on varieties not as adaptable to these programs.

• Cooler finishing temperatures in November impact bract expansion, another reason for selecting poinsettias with naturally large bracts to help compensate for any reduction in size.

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