January 2015 The Export Season and Ultimately The Valentine Production During the winter season in the North (including Japan and other countries), when floriculture production is low, there is demand for flowers and vegetables from places with year around cultivation. For India, export products have reasonably good prices and by sending produce out of the country, the lower quantity on the local market helps to maintain a reasonable and stable price level.
That offers an opportunity for the growers. Therefore maximizing production in this period has a strong reflection on the total year results. This is especially true for the rose growers with flowers for the Valentine. Rose growing is quite different from growing other flower crops such as carnations, gerbera, gladioli or chrysanthemum. In the other flowercrops we grow the flowers and harvest them, full stop. All attention is on the flower stems with no specific concern for the plant. In a rose crop we have to grow the plants and while growing them, we harvest flowers. If the crop is in good condition and when we harvest one flower we get one or two flowers the next time. The Dutch rose grower calls it ‘cutting flowers on the plant’.
If you harvest everything, including short and thin stems, you end up making the plant poor. As a result the number and quality of flowers comes down. Each plant has to have abundant (healthy) branches and leaves to be able to produce flowers; this has to be maintained for continuous production. Every set back is a reduction in productionThat is the reason that the present condition of a rose crop at this point of time is decisive for the Valentine production. In a few weeks we start pruning the crop back and the more and bigger stems we can prune, the higher the production will be. Ideal is cutting flowers and pruning mature stems. That situation can be built up by harvesting only strong flowers and de-budding the smaller ones in the 4, 5 weeks before pruning. By reducing the irrigation say 10 days before pruning, we allow the stems to store extra energy in stems and roots, necessary for strong sprouting afterwards.
The soil has a lot to do with the stand of the crop. The uptake of water and nutrients depends very much on soil conditions. Soil should be 40-50% porous for holding water and allowing for air. Soil humidity should be more or less stable. Nutrient uptake is subject to availability of elements in the soil solution, the balance between them and is further influenced by pH level (optimum pH is 6.3-6.5). Elements as K, Ca, Mg, Na and some micro elements, but also other elements, interfere with each other’s uptake either in synergy or antagonism. In practice it means that if e.g. high K is given, deficiency of Ca or Mg may be triggered and high N may limit the uptake of P. Some foliar feedingmay help to avoid hidden deficiencies.
There are many ‘growth boosters’ in the form of hormones, amino acids, special elements as silica or organisms as Azospirillum and Trichoderma available in the market. It is worth understanding the functions of these substances before applying them. The plant makes and consumes many of these organic compounds and elements and the soil contains uncountable organisms. By concentrating on an application of one or more of these materials, imbalance may be caused in plant and soil. After pruning the crop, wait till there is some swelling of the eyes and then start giving water and nutrients at a low level. Increase the fertigation according to development of the crop. Some extra ammonium may give a push to the initial sprouting.
Do not interfere with the sprouting by thinning etc. The plant is better able to decide which sprouts should develop. The smaller ones will help with photosynthesis. At this time of the year, we have to bear in mind the possibilities of diseases such as Downy Mildew, PowderyMildew and for some varieties Botrytis in the flower. A healthy plant is relatively resistant to fungal diseases. Sufficient Potassium and Calcium are important in that aspect. Recommended is the ratio K : Ca : Mg = 3 or 4 : 1 : 1. The risk for Downy Mildew is high when humidity is high and temperature is low. This condition is normally prevalent very early morning (sunrise) in the greenhouse. Ventilation at that point of time is very important. Temperatures above 28 degr. C during the day reduce the disease. Keeping the top soil dry-ish late afternoon; avoids high humidity during the night. Preventive sprays can be done with products containing metalaxil (eventually with mancozeb), cymoxanil, together with famoxadon. Products based on strobilurin are effective, even up to 3 days after infection.
Powdery Mildew develops with low humidity during the day, high humidity during the night and strong cross ventilation in the green house. Keeping the humidity above 60% during the day and avoiding wind in the green housewill help to keep this disease under control. A weekly preventive spray with sulphur (micronized W/P) will prevent the fungus from settling on the plant. If some spots are noticed, step in quickly with products containing penconazolhexaconazol, tebuconazol, difenoconazol or tridomorf and other compositions. Predators at this time of the year are less active and cause normally little problem. It is worth to keep an eye on surviving mites in the lower parts of the crop. They will jump back very strongly after February, when conditions are favourable. Keeping the basis of the crop and soil clean, removing old leaves and spraying, will avoid problems for later. In the following weeks the concentration is on growing strong sprouts and stems. Some red varieties are more sensitive to blackening of the outer petals than others. Avoid strong direct sunlight during mid-day (30% shade net is enough) and maintain air humidity above 60%. When it comes to harvesting flowers, make sure to undercut the stems as much as possible. At high price level every centimeter counts. When later the flowers are cheap, we can take care of the crop again. Last but not least, selling quality flowers this year, will help build a market for years to come.