10 years of Summer School Greenhouse Horticulture

To celebrate the tenth edition, we spoke with Prof. Leo Marcelis and Dr. Silke Hemming, two of the programme's long-standing course leaders. Looking back over the past decade, they see a sector that has changed rapidly, but one in which some fundamentals remain remarkably constant.

When the Summer School started in 2015, greenhouse horticulture was already facing challenges around energy use, labour costs and availability, water management and crop protection. Those challenges have not disappeared. If anything, they have become more urgent.

"Ten years ago these issues already existed," says Hemming. "But they have accelerated because of societal developments and global events." The Covid pandemic exposed vulnerabilities in supply chains. Geopolitical tensions and trade disruptions further increased awareness of food security and self-sufficiency. 

According to Marcelis, this has changed the way many countries look at food autonomy. "We increasingly see regions asking how they can produce food closer to home and become less dependent on imports. Greenhouses are being recognised as part of that solution."

At the same time, climate change threatens open-field production due to water scarcity, extreme weather or harsh climates. From the Middle East to northern Canada, greenhouse horticulture is increasingly recognised as a way to build more climate-resilient food production systems.

Technological innovation has always been part of greenhouse horticulture, but the pace has increased significantly. One of the most visible changes has been the widespread adoption of LED lighting, particularly in regions where natural light is limited. More recently, artificial intelligence and data-driven growing have become major topics across the sector. 

"The connection between AI and horticulture was hardly there when we started the Summer School in 2015," says Hemming. "Today it is everywhere, driven in part by initiatives such as WUR’s International Autonomous Greenhouse Challenge."

Yet both experts stress that AI is not only relevant for highly advanced greenhouses.

"Even relatively simple greenhouses generate data," says Marcelis. "And almost everyone has a smartphone. That creates opportunities for growers around the world to make better decisions based on data." That way, data-driven decision-making is already becoming accessible to a much broader range of growers.

Another major shift is the growing focus on sustainability. According to Marcelis and Hemming, growers today are under increasing pressure to reduce energy use, optimise water consumption and minimise the environmental impact of crop protection.

At the same time, significant progress has been made. Integrated pest management and biological control, once concentrated in a limited number of regions, have become increasingly common worldwide.

Participants in the Summer School regularly arrive with questions about balancing productivity and sustainability. How can they reduce resource use without compromising yield and quality? How can they prepare for increasingly unpredictable growing conditions? Those questions may vary by region, but they are shared across the globe.

Knowledge exchange has always been one of the strengths of greenhouse horticulture. As a relatively small and highly specialised sector, it relies on professionals learning from one another and building on each other's experience.

According to Marcelis and Hemming, that has become more challenging in recent years. As companies have grown larger and the sector has consolidated, knowledge is increasingly kept within organisations rather than shared more broadly. "Companies are becoming bigger and more protective of their knowledge," says Hemming. "I understand why, but I still strongly believe in the value of learning collectively."

That is one reason why international programmes such as the Summer School continue to play an important role. Each year, participants bring together experiences from different countries, climates and production systems, creating opportunities to learn from challenges and solutions far beyond their own region.

When asked what advice they would give to professionals entering the sector today, both experts arrive at a similar conclusion: understand your own context. A technology that works well in one country may not automatically succeed somewhere else. Climate, market conditions, infrastructure, available knowledge and local resources all influence what is possible.

Hemming also stresses the importance of understanding uncertainty and evaluating the impact of technical choices on production, resource use and sustainability. Marcelis adds that these decisions should always be viewed as part of the wider production system.

"Design a production system that fits your climate, your market and your local socio-economic circumstances," he says.

In other words, successful greenhouse horticulture is not about copying what works elsewhere. It is about designing a system that fits local conditions and making informed decisions based on reliable data, practical knowledge and a clear understanding of the trade-offs involved.

After ten editions, the Summer School Greenhouse Horticulture continues to bring together professionals who share a common ambition: producing more with fewer resources while building resilient and economically viable food systems for the future.

The technologies may evolve, and the challenges may become more complex, but the need for knowledge, collaboration and innovation remains as relevant as ever.