Knowledge session Agrolux, Ledgnd & Duijvestijn Tomaten GreenTech 2025

Switching to LED lighting in the greenhouse doesn’t just mean replacing the lamps, it also requires a shift in cultivation approach. That was the central message during a knowledge session at GreenTech, where plant physiologist Kees Weerheim (Ledgnd) shared practical insights from a joint project with Duijvestijn Tomatoes and lighting supplier Agrolux. The session made it clear that the true value of LED technology lies not only in the technical innovation itself, but in the grower’s ability to truly listen to the plant.

Duijvestijn Tomatoes has fully transitioned to a complete LED installation from Agrolux. “A major decision,” says Weerheim, “because you’re not just replacing a light source, you’re changing the entire greenhouse climate. Evaporation, air movement, temperature distribution, the plant suddenly experiences its environment in a completely different way.” Together with Ledgnd, an intensive process was set up with a clear goal: not only to make optimal use of the LED system, but also to understand how the crop responds to it.

In his presentation, Kees quickly dispelled the common assumption that more light automatically leads to more photosynthesis. Using real-world data from the Duijvestijn Tomatoes greenhouse, he demonstrated how two days with exactly the same daily light integral (DLI) still resulted in nearly a 50% difference in photosynthesis. “The difference was in the ventilation strategy,” he explained. “In one case, the plant was stimulated; in the other, it was held back. Without the data, we never would have seen this. It’s precisely these kinds of insights that lead Duijvestijn and their cultivation team to consciously make different climate decisions than originally planned. By working as a team and responding to both data and plant feedback, they are able to continuously take their cultivation to the next level.

This data came from a closed feedback loop, referred to by Ledgnd as the “Closed Feedback Loop.” It consists of three components: climate data (such as light, temperature, humidity, and CO₂), plant feedback (including photosynthesis, transpiration, and stress signals), and active decision-making by the grower. It’s not the system settings that take the lead, but rather the plant’s response to those settings. “If you do it right, it’s the plant guiding you, instead of the other way around,” says Kees.

In the project, plant feedback was visualized in part through MyScore, a graph that combines various crop health indicators into a single overview. “You often detect changes days before you’d notice them with the naked eye. And you can also spot irregularities that you wouldn’t otherwise measure at all.” At Duijvestijn Tomatoes, for example, it was discovered that a deviation in the RTR strategy not only led to increased use of plant reserves, but also to reduced assimilate production. “The plant becomes more unbalanced than you’d expect. This was an unexpected outcome that only became visible through the measurement of plant feedback.”

The session also emphasized the importance of spectral information. LED technology makes it possible to use specific light colors, such as red, blue, or far-red, independently. According to Kees, this is not a minor detail but a defining factor: “Different spectra trigger different physiological responses, both in photosynthesis and in morphological development.” These insights, he explained, are essential for growers who want to get the most out of their LED system, especially when aiming for quality and uniformity in crop production.

The session clearly attracted a great deal of interest, particularly from growers already working with LED who are still seeking more control over the process. Kees had a clear message for them: “LED is not plug-and-play. It requires a different mindset, and close collaboration between the grower, the technology, and the plant.” According to him, it all starts with reliable data. “Only use tools you trust. Measure what matters. And truly put the plant at the center.”

The collaboration between Agrolux, Duijvestijn Tomatoes, and Ledgnd was presented as a model of how technological innovation, practical experience, and plant physiology can come together. The focus wasn’t on the LED lamp itself, but on a deeper question: What is the plant telling us about the impact of our actions?

The knowledge session concluded with a call for self-reflection. “Dare to reconsider your decisions when the data tell you something different than your intuition,” Kees urged. “Because LED, in itself, is no guarantee for success. What matters is how you use it, and in that process, the plant is your most reliable advisor.”