Modified cultivation strategy
The first plants went into the ground in mid-November, to be harvested at the end of January. This was the only crop on which both types of lights were used together Grootscholten points to steeply rising energy prices as the reason.
“The cultivation results were perfect, but it’s just too expensive to use HPS lights,” he explains. “So we had to adjust the cultivation strategy. In the lighting season, which in our case runs from mid-September to the end of March, we maintain a slightly lower plant density. This allows us to continue growing high quality products with the available daylight and LED lights. The LEDs basically run at full capacity, except during the most expensive hours, when the installation runs at half capacity. The HPS lights are only on in the rows where harvesting and planting is taking place. It’s nicer to work in their white light. The rest of the time it looks pink in the greenhouse.”
By turning off the HPS lights, and maintaining a lower plant density, the nursery misses out on 10 to 15% of production compared to what was expected. “The 10 to 15% reduction is a shame,” he says, “but we have now learned that you can also grow good chrysanthemums under full LED.”
Due to the absence of the radiant heat of the HPS lights, the greenhouse climate needs a bit more attention. However, the nursery has air conditioning units that contribute to a homogeneous greenhouse climate and efficient moisture control, and the blackout and energy screens limit heat loss.