The amaryllis is not a shade plant, but is not really a sun lover either. Up until the cool period, it can use all the light it can get in the summer, as long as this does not lead to excessively high leaf temperatures. “The arrival of ReduFuse IR presented us with the perfect coating: sufficient diffuse light and a lower leaf temperature because of the reflection of infrared radiation”, says Jan Overkleeft. He is an independent consultant who advises the majority of amaryllis growers in the Netherlands. The advance of coatings in the cultivation of this crop is largely thanks to his recommendations.
The cultivation of amaryllis is concentrated in the regions Huissen, Noord-Limburg and the Westland, regions with very different climatic conditions – it is much warmer and wetter in the east than on the coast. The yield per square metre is, however, such that new construction is not feasible and many amaryllis are grown in old, low greenhouses.
ReduFuse IR fits in perfectly
“A combination of ReduFuse and air humidification is adequate in contemporary high greenhouses, but not in lower greenhouses. In the past, ReduHeat was often used because ReduSol is not suitable, the problem being that it reduces too much light, thus reducing growth. ReduFuse IR was just what we needed: it is the perfect coating. Only growers with a very limited cooling capacity sometimes still have to use ReduSol on top of it”, he continues.
Overkleeft tells growers that they hardly need to use screens if they use ReduFuse IR. Diffuse light penetrates deeper into the crop and the plant can use any amount of this diffuse light. “If the leaf temperature does not rise, the stomata remain open longer and assimilation goes on longer too. The first thing that struck me when ReduFuse IR came onto the market was that the bulbs became bigger”, the advisor says. “And bigger bulbs mean better stem quality. You can harvest sturdier stems, assuming of course that the other cultivation measures are properly observed.”
You only need to close the screens for a while if the greenhouse temperature rises to 30-32 °C in the summer. “At temperatures like that there is no growth anyway so it is all right to reduce the light. In that case, you shade the crop to keep it healthy”, he adds.
Overkleeft recommends application of the coating around 1 April and to leave it until the harvest begins in October. Three quarters of Dutch amaryllis growers currently use a coating. “And people who start using it, stick with it”, he observes. He is very positive about Mardenkro's approach. “They always give you plenty of background know-how. They explain how something works, give good information and, if something goes wrong, they solve it without problems. They also invited amaryllis growers to come and visit the factory at one point. I am very enthusiastic about the company.”
Overkleeft follows the development of new innovative coatings with interest and is receptive to new possibilities.
He feels that coated greenhouses could also contribute to better quality amaryllis bulbs. “Growers lift bulbs around 1 August and in the months prior to that you could boost growth under a diffuse coating. That would benefit the quality (the size of the bulb). But bulb cultivation is also under pressure and the costs have to be carefully considered. We do not have much experience yet, but growers who have jumped on board, are enthusiastic and do not revert to their old ways”.
For more information
Mardenkro The Netherlands
5111 PS Baarle-Nassau
T: +31 (0)13 507 70 69