In the past few years, I’ve seen more and more growers across the globe adding LED grow lights to HPS to increase light levels and yields for their gerbera daisies. Unlike high pressure sodium (HPS) lighting, higher light levels can be applied with LEDs because they produce very little radiant heat and use less electricity. 

This enables growers to achieve the perfect balance between warmth and light with LEDs, so that they can produce more crops and potentially accelerate the payback on their LED investments.

One of the research trials that has affected my work as a plant specialist in floriculture was carried out in 2013 and 2014 by researchers at Wageningen UR in Bleiswijk, the Netherlands. They performed several trials using different light strategies to grow gerbera crops. These included trials with: HPS lighting alone, a hybrid system with HPS and LED lighting, and a full LED system. The main goal was to look at possible ways to save energy usage in gerbera production without reducing quality or production. The plants were also tested for their resilience against Botrytis. A concern was that the lower heat levels of LED would increase condensation on the flowers which might make them more susceptible to Botrytis spores.

The trials confirmed that the relationship between warmth and electricity in the greenhouse climate changes with the use of LED lighting. In the greenhouses with HPS lighting, the radiant heat from the HPS modules gradually warms up the crops. This warmth is needed to maintain the right balance between the crop temperature and amount of light. In the LED greenhouses, heated pipes were used to create extra heat. Even though natural gas was used to generate the extra heat in the LED greenhouse, the energy costs were the same as for the HPS greenhouse.

However, growers who lack extra electrical capacity stand to gain the most from LED lighting. They can use less energy to increase lighting levels and lighting hours with LEDs compared to HPS. An extra advantage is that heating and lighting can be separately controlled. The hypothesis that more Botrytis would develop with LEDs was proven to be unfounded. The researchers concluded that both hybrid, HPS, and full LED lighting systems can be used to produce the same quality and yield of gerberas without extra Botrytis.

The results from these types of research trials have made it easier for growers to apply LEDs in their own greenhouses. In August 2016, I participated in a project to support a European gerbera grower supplement part of their existing HPS lighting installation with LED grow lights. Together with the grower, I supported setting out a registration plan to compare their production results with HPS to their production results with the HPS and LED system. This would give us and the grower feedback from a commercial application as well as insight into aspects that might require further optimisation.

In the first winter of 2016, the company’s production was already in line with the expected increase, thanks to the higher light levels achieved by applying LED lighting. The quality of the crops was also excellent. After the winter, the grower felt that it would be possible to further increase the yield with the hybrid lighting system by raising the temperature in the greenhouse, and so also the crop temperature. In the second year, the growth time was monitored and the daily temperature in the greenhouse with hybrid lighting was raised. Based on the data, the same growth time was achieved for the HPS standalone system and the hybrid HPS and LED system. Production went more smoothly and the quality remained consistently high. There was also no sign of extra Botrytis in the hybrid greenhouse.

We see a rapid increase in the number of growers around the world who are adopting and optimising LEDs to improve their yield, quality and production costs. At Philips lighting we continue to partner with researchers and growers to further improve our light recipes in this area, and we have confidence that LEDs are one of the keys to success in the future.