Among those exports, it's perhaps not surprising that the tulip is no longer queen of the Dutch blooms. Instead, pick of the pops are chrysanthemums, grown by nurseries such as Zonnehoek in Kwintsheul. Zonnehoek is actually bucking the trend of fewer hectares: their three hectares of glasshouses, only six years old, it set to increase in size following the acquisition of another site, and continued investment.
One particularly pertinent example in the ornamental market is plant growth regulation. Where traditional flower wholesalers might have been content with long stems, up to 75cm in length, to allow for trimming and so on, today's supermarket buyers - who in the UK account for 60 per cent of the cut flower sales - dictate far more stringent requirements. They want stems no longer than 65cm and there's very little room for variation - which requires close attention to detail from Zonnehoek's Crop Consultant Jon Krouwer. He makes a weekly visit to the greenhouse to assess the crop and advise upon any necessary treatments. Each crop is different, he says; so daminozide dose rates (in this case, Fine Agrochemicals 'Dazide ENHANCE') have to be tailored to suit. It's certainly clear how even small differences in PGR use affect the plants growth. What's more, each cultivar has to be 'learnt', how it responds to climate performance in the greenhouse, and so on, with seasonal changes often exaggerating the difference. For example, summer crops of Deliflor's Delianne spider cultivar can often require up to twice the PGR dose rate of those grown in winter. With Zonnehoek shortly planning to switch to the Anastasia cultivar, Jan will be paying close attention to the first crops to see how the cultivar reacts to changes in temperature, humidity and soil moisture. That will provide the information needed to tailor daminozide applications: how much to apply, and when to apply it.
"In Holland, greenhouse growers seem to demand a far greater input from their agronomists than is normally the case in the UK", says Wilbert Flier, Fine's technical services manager based in the Netherlands. "But the more regular visits certainly seem to pay off, as both the agronomists and client have greater contact and know more about crop progress and development. "That's particularly important when using a product such as Dazide ENHANCE, which many growers see as an essential management tool", he continues. "The compact growth bud formation that the product encourages are precisely what the auction buyers here in the Netherlands are looking for".
Zonnehoek complements the use of Dazide ENHANCE to fine-tune plant growth and development with a comprehensive system of automated blinds and shades throughout the greenhouses, which force the plants into 'long-day' and 'short-day' photosynthesis modes. Chrysanthemums are naturally short-day plants: that is, they form their flowers only when the day length is less than 12 hours. So by keeping the plants on a long-day regime, the amount of vegetative growth can be controlled, before switching to short-day to force the plant into flowering.
Article supplied by The Commercial Greenhouse Grower - April 2006