Guest article: The salad revolution

Take a look inside a very special greenhouse.

From the outside, the greenhouse looks like any other, only significantly larger and with a roof through which you can glimpse the green of the plants. It stands in the middle of fields and forests in Willich, Düsseldorf. But even at first glance, visitors get a hint that they will certainly find many things here, just not a normal salad greenhouse. When Harrold Thijssen opens the doors to the Rheinlandhof, you feel as if you have been transported into the future: young lettuce plants float in several huge ponds covering an area the size of four football pitches. In the background, you can hear the soothing sound of splashing water, but also the slight whirring of robots as the lettuce plants move slowly and as if by magic along long waterways running through the hall.

But let's start at the beginning. At Rheinlandhof, we find ourselves in Germany's most modern salad greenhouse. When summers in Germany became increasingly hotter and drier and the weather increasingly unstable, and when he saw images of drought in Spain and Italy on the news, Harrold Thijssen knew that something had to be done. The Thijssen family has been growing lettuce for four generations. But: ‘In times of climate change, it is becoming increasingly difficult for us farmers in particular to grow high-quality vegetables efficiently and without consuming large amounts of resources. Because, of course, we don't want to use more water than necessary,’ explains Harrold Thijssen, adding: ‘This is now difficult to achieve in outdoor cultivation under these weather conditions. The solution is our new greenhouse with innovative cultivation technology that has hardly been used in Europe to date.’

What Harrold Thijssen is referring to are the huge ponds in the greenhouse, which are fed exclusively by rainwater collected from the greenhouse roof. The lettuce plants grow on these ponds on many individual floating trays. The advantages of pond cultivation in terms of sustainability are obvious: not a single drop of water escapes from the closed pond system, so the lettuce plants are guaranteed to be watered even in times of drought, and greenhouse cultivation saves 90 per cent of water compared to field cultivation. By using rainwater, the greenhouse is also completely self-sufficient and does not need to rely on other water sources. But the water has another advantage: nutrients such as calcium and magnesium can be dissolved in water, which means that the plants require 75 per cent less fertiliser. This also protects the groundwater, as neither fertiliser nor any other nutrients escape from the closed pond system into the groundwater.

This is an advantage that Kaufland has also recognised. The food retailer has always focused on regional sourcing when designing its product range and also attaches great importance to modern, environmentally friendly cultivation methods. This makes Rheinlandhof the perfect Kaufland partner for supplying salads. ‘Whether it's climate change, water scarcity or the energy transition, agriculture, and vegetable cultivation in particular, is facing challenging times. For us as a company, it is important in terms of sustainability to offer regional products that can be grown in Germany throughout the year in the most resource-efficient way possible,’ says Stefan Lukes, Managing Director of Fresh Produce Purchasing at Kaufland, adding: ‘The collaboration with Rheinlandhof is a successful example for us, showing that we can offer sustainable, high-quality food in every season without having to forego regional delivery or collaboration with family businesses.’

What's more, this modern cultivation method is particularly efficient. The greenhouse ensures that the lettuce plants are always kept at a constant temperature. The Thijssens use a sophisticated system to achieve this: special glass is used for the greenhouse roof to ensure that as much light as possible can be absorbed from outside without losing too much energy to the outside. The heaters, which are needed for the small plants, especially in winter, can be turned down so that heat is only used where it is really needed. LED and Son-T lighting ensure that the lettuce can grow well even in winter when there is little sun. In the greenhouse, the lettuce plants are also protected from external weather influences such as hail or heavy rain. This minimises crop failures, ensures that the lettuce is of very high quality and can be grown all year round. This means that Harrold Thijssen and his team can harvest up to 10 million root ball lettuces throughout the year. This makes the yield in Germany's most modern lettuce greenhouse up to 25 times higher than in conventional outdoor production. Thijssen also explains what makes root balls so special in terms of sustainability: ‘The root ball means that the lettuce can be kept in the refrigerator for much longer. This also helps us to combat food waste, as the lettuce stays crisp and fresh for longer.’

What is also special is that Rheinlandhof is much more than just a greenhouse. From sowing to harvesting and packaging, everything is done here in one place, from seed to ready-to-sell salad. Specifically, it is only a few metres from the hall where the small seeds are planted using modern robot technology, through the germination room to the ponds and finally to harvesting and packaging. This reduces transport distances, saving CO2 – and everything happens from a single source. The Thijssen family knows their lettuce from seed to plant better than almost anyone else. Farmer Thijssen and his employees at Rheinlandhof are supported by state-of-the-art automation technology in Germany's most modern greenhouse. Automated waterways help to transport the goods in an energy-efficient manner, and robots developed specifically for Rheinlandhof are also used. For example, a robot already takes care of transplanting to larger pots, as well as planting, initial watering and root trimming. In future, robot arms will also take over the journey from the pond to the automated waterways. This not only reduces the workload for employees. The use of robots is also extremely hygienic, improves and speeds up processes, and ensures that the lettuce is available in Kaufland stores within a few hours of harvesting. This means that customers can enjoy ultra-fresh lettuce and multicoloured salad all year round. And if Thijssen has his way, this will not remain a one-off: "With our greenhouse, we want to revolutionise vegetable cultivation in Germany. In times of climate change, we as farmers are already facing immense challenges that will only increase in the coming years. Climate-friendly cultivation on pond cultures can be used almost anywhere in vegetable cultivation and could thus be the solution to how we can continue to offer our customers delicious, fresh vegetables from the region in the future without compromising on sustainability."

Kaufland will be represented at Grüne Woche 2026 in the ErlebnisBauernhof (event farm) in Hall 3.2.