Fig 1 - Light stress in plants caused a 8% cumulative productivity loss, equivalent to 7 mol/m2 of photosynthesis. Hypothetical strategy which shaded at 900umol would have achieved more total production despite lower light sums.

In April 2025, De Peelkroon, a leading Dutch strawberry grower, trialled a no-shading approach during high light intensities, hoping to boost growth. Crop observations suggested that the plants were performing well, but Gardin's real-time plant data showed a different picture. Photosynthetic efficiency breached safe thresholds, and night-time recovery was poor, pointing to unseen light stress. The crop suffered a 8% production loss in just one month.

Gardin's feedback has now changed how shading is used at De Peelkroon, helping the team protect plant health during high-light conditions and maintain yield potential over the long term.

April 2025 saw a sustained period of unusually high light combined with a dry and relatively cool climate. This created a challenge for growers by straining Vapor Pressure Deficit (VPD) conditions. Under these conditions it is common to apply shading to reduce incoming light levels and raise greenhouse humidity.

De Peelkroon are a leading strawberry grower based in the Netherlands with over 4 hectares of strawberry crops owned and operated by Rob Van Enckevort. Given the high light available early in the season, instead of applying shading as usual, Rob allowed light levels to rise freely, testing the impact on greenhouse climate and plant performance.

On April 3rd, the shades were left open and PAR levels allowed to reach above 1,000 µmol/m²/s and peak near 1,200 µmol/m²/s. Inside greenhouse temperature peaked at 24°C and leaf temperature at 32°C. April 4th had a very similar outside climate but on this day the shades were closed, the inside greenhouse temperature reached 26°C and the leaf temperature fell to 28°C.

Whilst 32 degrees would normally be regarded as a very high leaf temperature that would cause stomata to close, transpiration and water usage was actually higher on the day without shading. Most growers would typically observe this as the plants coping well with the high light and having a positive impact on rates of photosynthesis and water movement through the plant.

Fig. 2 Left: Rob van Enckevort, Owner and Grower at De Peelkroon. Right: Mark van der Werf, Plant Health Consultant from Plant Empowerment.

Plant productivity is calculated by combining the expected light use efficiency and incident light (PPFD), to give the electron transport for photosynthesis. The lack of shading and resulting plant stress resulted in a cumulative assimilate deficit over time. In April, this deficit reached 10% in both monitored greenhouse sections. Based on Gardin's historical yield models, this loss would correspond to an estimated 6% reduction in strawberry yield.

The model also indicates that if shading had been used to cap the canopy-level PPFD at 900 µmol/m²/s, total productivity would still have been higher by the end of the month. This provides compelling evidence that an informed shading strategy does not reduce growth; due to the long-term benefits of mitigating light stress on photosynthetic efficiency.

Final Photosynthesis Results

These results highlight the critical need to evaluate greenhouse climate strategies through the lens of plant photosynthesis. Not doing so risks drawing incorrect conclusions which can result in significant losses in monthly production of 10%. In this study, high transpiration levels gave the impression of plants coping well under bright conditions, but this led to an incorrect shading strategy and caused long term damage to the plant photosystem.

Rob reflected on these insights from Gardin - "We pay much closer attention to the shading strategy now we work with Gardin, and take better steps to plan for periods of high light, like we have seen this year. Gardin has helped us to think more about the long term effects of our crop strategy on plant health rather than just choosing short term gains".

Gardin offers an easy to use, fully autonomous system for monitoring crop photosynthesis. Its insights help growers target the optimal climate strategy, including lighting and shading to maximise yield at the lowest cost.