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| Holding bedding plants for sales | |
| In order to maintain bedding plants in the best possible quality for sales, certain facts need to be observed. Irrigation should be reduced at the visible bud stage to allow the substrate to dry out more thoroughly. Too much water at this stage can cause elongation of the internodes and provide conditions that favour root rotting diseases. An open-sided covered area for holding the bedding plants is adviseable to shelter plants from rain. This is essential for varieties with large delicate flowers (to avoid Botrytis and toppling over). A cover will also prevent rain from causing excessive leaching of the substrate. Water quality is important. A test of the pH and EC conductivity should be made. High alkalinity can have a major effect on reducing the availability of micro-nutrients. High pH is often associated with iron deficiency and can ruin a crop. An acid residue fertilizer can be added to compensate but may introduce toxicity of micro-nutrients or macro-nutrient deficiences. In highly alkaline water, an acid NPK formulation of 20-10-20 can be used. Where alkalinity is lower, a formulation of 15-5-15 is indicated. Most bedding plants demand medium to moderately high light levels during production. Light levels should be reduced during the holding period. Intense sunlight should be avoided and plants can be shaded when temperatures rise to 20°C or above. The shading will reduce air temperature and water requirement. Light levels should be maintained at 2700-7500 lux. Trolleys of plants should be placed in areas where light can penetrate the shelves but at the same providing some shading for plants on the top shelves. Cool temperatures will slow growth and flowering while warm temperatures will increase demand for water and increase rate of growth and flowering. When temperature is reduced the respiration rate decreases, plant matabolism slows and carbohydrates/sugars begin to accumulate. This can benefit quality in the post production phase. It is suggested that temperatures are reduced to 5°-8°C during post production. Lower temperatures will also enhance tissue colour (brighter flower petals and leaves). However, lower temperatures combined with high relative humidity can lead to disease. High fertilizer concentrations should be avoided before marketing. High concentrations can lead to too much growth and leggy plants or an EC high enough to damage roots. A low phosphate/amoniacal nitrogen fertilizer should be used. High levels of phosphate will increase stem elongation and ammoniacal nitrogen causes lush vegetative growth and less flowering. Use an NPK formulation of 13-2-13, 15-0-15 or 15-5-15 once a week with Nitrogen at 50 -100 ppm. It is important to maintain air-flow, also to reduce the accumulation of air pollution. Try not to pack plants to close together; adequate pacing will prevent disease and reduce the drop of the lower leaves. The substrate in larger pots will hold more water and for most bedding plant varieties this means that the plants will require watering less frequently. Substrate should be well aerated with a sufficient water holding capacity and proper drying time. The substrate selected should retain the nutrients necessary for growth and development of the plants. Plant growth regulators can be beneficial in making plants more compact with greener leaves and with a reduced water demand during the post production phase. James. L.Gibson and Shannon Crowly, University of Florida. E-mails: jlgibson@mail.ifas.ufl.ed and SRCrowley@mail.ifas.ufl.edu Ofa Bulletin 884 www.ofa.org |
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