Summer is in full swing in the Netherlands, and it's clearly noticeable in greenhouses where crops are soaking up the abundant sunlight that these months bring. But more sun isn't always better. Just like people, plants have their limits. Every fruiting vegetable crop has a maximum light requirement. When that threshold is exceeded, problems can arise.
© ProJoules
Sunlight: power and vulnerability
Sunlight is essential for photosynthesis—and therefore for growth and yield. But when light levels surpass what the crop can effectively process, it creates stress. This can lead to quality issues such as sunscald, blossom-end rot, irregular fruit set, or growth stagnation. These risks are especially high during prolonged periods of intense sun and heat, when the plant's limits are quickly reached.
Insight yields results
Determining a crop's maximum light requirement isn't a matter of guesswork, it requires a solid understanding of the variety, the growth stage, and the conditions inside and around the greenhouse. In practice, however, it's often difficult to accurately assess how much light plants are actually receiving. Light levels fluctuate from day to day, hour to hour, and even between different sections of the greenhouse. This variability is exactly what makes managing light balance so complex.
To get better control, more and more growers are turning to data and digital tools. One such tool is ProJoules, a platform that supports crop planning and offers insights into light accumulation at the plant level. By combining this information with crop-specific knowledge and growing strategies, growers can gain a much clearer picture of how much light their crops can handle.
"You're not just responding more effectively to today's conditions," explains Wim van Wingerden, the creator of ProJoules. "You're also able to anticipate and make timely adjustments. It turns light management into a concrete, data-driven process."
© ProJoules
Light plan ProJoules. Click here for enlargement.
Smart light management
One well-known method for managing light in the greenhouse is applying a coating to the greenhouse roof. By selectively filtering sunlight, this helps keep the crop in balance, even during periods of peak radiation.
Another common option is the use of shade screens. While these do block light, they often still allow heat to pass through, which can be a limitation in hot weather.
"By using PAR meters, both inside and outside the greenhouse—growers gain a much clearer understanding of actual light intensity," experts explain. "Those who manage light effectively can prevent crop overload and maintain both high productivity and strong fruit quality."
© ProJoules
Looking ahead to autumn
What a grower does today has a direct impact on how the crop performs later in the season, explains Wim, himself a former grower and now a crop advisor. "A plant that experiences too much stress during the summer often struggles to recover and will underperform in the autumn. That's why it's so important to invest now in knowledge, monitoring, and smart tools like optimizing light levels and using data-driven growing strategies. This builds a resilient crop that continues to perform well long after summer ends."
Want to know more?
Curious how ProJoules can help optimize light use and crop planning in your greenhouse? More information can be found on the revamped ProJoules website, where practical examples are provided and you can request a demo to get started yourself.
For more information:
ProJoules
info@projoules.com
www.projoules.com