Mathieu van Holstein, Holstein Flowers

“Our decision to start with Next Generation Growing has proved to be the right one”

Five years ago, Holstein Flowers decided to start with Next Generation Growing and became a pioneer with this installation in gerbera cultivation. It started with a Technokas air handling and dehumidification installation. Mathieu van Holstein looks back on this decision with satisfaction. "We now have a tool with which we can do more than in a traditional greenhouse. We can grow all varieties well with it, including the sensitive ones.”

Holstein has been growing gerberas since 1974. In 2017, the nursery in De Lier covers 11 hectares, where both production and in-house breeding take place. "We focus on the wholesale/florist and the retail top segment. In-house breeding has become more and more a priority: now 80 to 85% of our varieties are ‘home-made’. Our aim is customer loyalty. We grow for the premium segment and that also includes exclusive varieties", explains Mathieu.

Regulation range

"Our relationship with Technokas started in 2011," says Mathieu. "We were looking for a technical consultancy firm with which we could go into depth. We had heard about Technokas. They had built a greenhouse for a colleague of ours. But we're not the kind of people who build something because the neighbour does so. We wanted more depth, and time to have things sorted out. I also participate in various supervisory committees of Next Generation Growing. Improvement Centre (IC) Bleiswijk has been researching it since 2008/2009, and we have been interested ever since. Our locations from 1984 and 1989 were no longer up-to-date. We decided to rebuild 4.5 hectares, of which 1 hectare with dehumidification with hoses under the crop. This is how they did it at the IC in Bleiswijk at the time.”

Mathieu opted for Next Generation Growing with air handling units with a relatively small capacity of 5 m3/m2/hour. "You can't beat the outdoor conditions with that, but this was never our intention. Bridging the night period was what we aimed at. During the night, there is less evaporation and that’s something the installation can regulate. The basic rule is: the less a plant evaporates, the less you need to dehumidify. The plant does not have to stand still, but it does not have to grow full steam either, because that is not favourable. There must be a minimum amount of evaporation that is functional for the plant, the rest is unnecessary. But you don't want botrytis in the crop and that's exactly what the installation is meant for. So it was a question of looking for an installation that could remove just a little more moisture than the plant evaporates, because that allows regulation range.”


Next Generation Growing was so successful that two years later, the remaining 3.5 hectares were also equipped with a climate control system. Only now Mathieu chose to hang the hoses over the crop, instead of underneath, throughout the entire greenhouse. "That was an important lesson. With hoses under the crop, you are always pressing the evaporation of the plant. Now it works satisfactorily.”

What are the advantages? "It's energy efficient. We need to do less with minimum tube, the humidity can be better regulated, and we also use less energy. We can keep our cultivation more easily away from the risk factors. We have several sensitive varieties in our range. In 2012, we introduced a new spherical product with many more ribbon leaves, but we had trouble growing them without any botrytis. We now have a tool with which we can do more than in a traditional greenhouse. We can grow all varieties well with it, including the sensitive ones.

Mathieu estimates energy savings of 5 to 10%, but that is a deliberate choice. "It depends on how you turn the wheel. You can opt for maximum energy savings, but then you have no climate improvement. And if you opt for maximum climate improvement, you have less savings. The climate is very important for us, because we want to deliver a high-quality product, without any complaints further down the chain. We want stronger flowers, more flowers and a less disease-sensitive product. So it's all about finding the right balance. We regulate the dehumidification capacity and humidity deficit and can adjust these quite precisely. Although it does depend on the outside conditions: the drier the air is outside, the more regulation range you have.


There were no real practical experiences with Next Generation Growing in 2012. "That's why we spent quite some time looking for the right installation. Researcher Arie de Gelder of Wageningen University Glasshouse horticulture was involved. We measured and calculated the evaporation, which resulted in a crop evaporation of 12 grams of moisture per m2 per hour. Technokas studied the growing conditions in the Netherlands, the growing conditions on our nursery, the differences with the outside situation, how often a year these differences occur, and how big they are.”

"We actually wanted to be able to dehumidify between 12 and 15 grams. Technokas then indicated that with this installation it would be possible to dehumidify 3 grams per m3, and that with a capacity of 5 m3 it would be possible to dehumidify 15 grams. It would be minimally feasible in 85-90% of the cases. The colder the air, the drier it is. But you do not bluntly want to blow cold air into the greenhouse. The air must be heated, which costs energy. That is why the installation is not more powerful designed than necessary. Technokas has succeeded particularly well in this. In the end, they fulfilled the expectations of the calculations they made in advance. Our decision to go for Next Generation Growing turned out to be the right one.


After the development phase, Technokas Engineering (formerly Bode) was also given the opportunity to submit a tender for the construction of the greenhouse, including heating, Next Generation Growing and a business facilities. "This was certainly not a done deal in advance, but the price-quality ratio was decisive for us. Looking back, I am very positive about the cooperation and about the combination of development and construction. The fact that they have everything in-house was something I was quite happy about afterwards, because it strengthened the project. Our initial approach was a little different. We did not really worry about the project, because we would be there ourselves to monitor every step on the way. However, their role was much more important than we had anticipated. Until the very completion of the project they were involved in thinking about improvements, also improvements that had not been discussed before. So along the way, some smart modifications were implemented, of which we were certain that they would suit the project better.

“For example, the trellis girder in the greenhouse was carried out lower than planned”, says Mathieu. "I think that's typical of Techno. You submit a problem, and they start contributing ideas. We wanted double screens, but then you end up with a wider screen package. So we asked if it would be possible to construct a smaller trellis girder. They started to investigate, and to their own surprise found out that the trellis girder could indeed be a lot smaller. We also commissioned TNO to carry out a study into shadow calculations, which also proved positive. An extra advantage was that we got a smaller air cavity between the screens, which results in a better insulation value.

Would you recommend Technokas to your colleagues? "Yes, especially if you need special things that deviate from the standard. And if you want to get started with Next Generation Growing, of course. I'm not saying that it's not possible with someone else, but they're very good at it, both in design and construction," says Mathieu.

Technokas has carried out the following activities for this client: custom-made greenhouse, heating, air handling and dehumidification, business facilities, advice & guidance.