Screens hardly needed due to coating

The 3.2 ha nursery in Varik grows the special chrysanthemum Madiba, a small-flowering Santini. “It’s a crop that requires a lot of attention. The flowers are small and the leaf too. The small volume of crop makes it difficult to control the climate,” says John van de Westeringh.
“In addition the flower colour fades if it receives too much sun. We produce year round and we want to consistently supply the same flower colour. In the summer we had to manage that with a shade screen.”

Screens with blackout cloth

He used to screen with a blackout cloth and when it was sunny it was 80% closed. It was not the ideal situation because it gave an uneven distribution of light and humidity in the greenhouse and therefore uneven growth and colouring. “In the summer we had to close the screen every day, also for the working conditions,” says the grower. Last year he applied ReduHeat to the greenhouse roof; a small part was coated with ReduFuse. This year the largest part has again been coated with ReduHeat and a trial area has been coated with ReduFuse IR. The coatings were applied during the second week of April.
It’s a world of difference compared with the old situation. “We are now satisfied with the flower colour and growth. In addition we can ventilate later and therefore keep more CO₂ inside. We wouldn’t want to grow without a coating anymore,” says van de Westeringh.

Heat reflection

Next year he will probably cover the whole roof with ReduFuse IR. “It’s heat reflecting properties are similar to ReduHeat and then the cost will be the deciding factor. Up until now we haven’t noticed any difference in plant quality between ReduHeat and ReduFuse IR. That was different last year when we tested the ordinary ReduFuse. This coating was less suitable for our crop because it let in too much heat which meant the flower colour was not optimal.”
An additional advantage of the coatings is the benefit to the natural predators. The nursery uses predatory mites in breeding sachets. If the sachets become too warm the mites don’t multiply as well which ultimately can lead to problems from thrips.

No more screens

“The screen no longer has to used to shade the plants. Sometimes when we’re harvesting we close it for a few hours to make it more comfortable for our personnel. But even under the coating it’s much more pleasant to work now that the sun is not shining directly on your head.”
The climate control is much easier to run with the coating on the roof. The windows can remain closed for longer so the humidity and CO₂-level remain steady for longer. Both have a positive effect on growth. Watering has also been adjusted. “When there’s too much sun you have to water a lot and that can result in Phytium problems. That’s better now. The crop simple grows much better,” says John van de Westeringh.