Category: News
Date published: December 07, 2020

Tropical garden in the Netherlands


Rianne Lek, Senior Consultant

The tiled hall of the Omnium in Goes, the Netherlands, with its slight smell of chlorine, gives no hint that just one floor up, on the roof of the swimming pool, is a big surprise – Expeditie Bos, a lush tropical garden. The heat from the greenhouse is used to heat the swimming pool. Fertilization is organic and the plant protection fully biological. ‘Without Koppert’s products, it would not have been a success.’

Expeditie Bos is a 1,500 m2 greenhouse, eighteen metres high. It accommodates king quail, geckos, turtles, dart frogs, and 430 varieties of plant, which are grown in just 30 to 90 centimetres of soil. Since its opening in 2014, the vegetation has developed to abundance, with tall trees and climbing plants reaching up to the apex of the roof. ‘Most unusual are the tropical commodity crops that we have here – coffee, cinnamon, tropical fruits trees, pepper, and rice. We plant pineapple heads and ginger roots with children. They grow in no time, and ginger also blooms beautifully,’ explains Jan-Kees Karelse. His shirt bears the word ‘bosbaas’ (forest ranger) – officially, he is the operations manager. He has been responsible for the ins and outs of the garden, including the flora and fauna, for a year and a half.

Signal plants

Having both an educational and recreational role, the garden attracts visitors every day, so the decision to opt for biological plant protection made sense. Rianne Lek, senior consultant at Koppert Biological Systems explains, ‘The difference when compared with a productive farm is that these plants will stay here, so it’s easier to create balance between useful and harmful organisms. However, as the climate is not equally favourable for all plants, harmful insects still sometimes appear. That’s why we need to add biological controls.’ Koppert works with specialist Entocare on typical tropical pests.

‘Obviously the ecosystem is doing well, because everything is young,’ beams Karelse. He shows us a pot plant that is on display in the bar. There is a gecko egg between the leaves. The red-eared slider turtles have just laid eggs in the sand next to the climbing wall. The king quail population has grown to number 50. ‘Rianne often sees the second generation of her own products here, they also propagate,’ explains Karelse.

‘We can keep everything in perfect balance thanks to the diversity, care, and patience,’ he explains. ‘We have a signal plant for nearly every disease. Tobacco is particularly sensitive to whitefly, for example. If I see whitefly on the tobacco plants, I know to order some extra insect netting. Once it’s up, it’s a waiting game. A garden like this is like a diesel train – biological plant protection needs time to build up speed.’


Organic soil fertilization

Jan-Kees Karelse and Rianne Lek: ‘We can keep things nicely in balance’

Above the ground, Expeditie Bos uses predatory mites in insect netting to control spider mite, thrips, and whitefly and parasitic wasps to combat aphids.

Equally as important are the products that the garden uses below ground. Karelse explains, ‘We have a limited growing layer so we use organic soil fertilization like Vidi Funda. We hand-water every single plant, so we can see precisely what each one needs. We use Vidi Fortum to promote young shoots and stimulate good growth and Vidi Terrum to give stressed plants a bit of a helping hand.’ Lek adds, ‘Vidi Terrum contains a lot of easily absorbable amino acids.’

Fortafol, which improves the transport of nutrients into the plant, has a strong smell of eucalyptus. ‘We often have visitors tell us that they like to come to the garden in the evening and use it as an “escape room”, somewhere they feel comfortable. It smells like the garden has been cleaned for them,’ laughs Karelse.



‘Without Koppert Biological Systems, we would not have succeeded in keeping the balance that we have in the garden,’ says Jan-Kees Karelse. ‘Not just the products, but the advice as well. I regularly go scouting through the crops: I photograph every beetle that I don’t recognize and send the photograph to Rianne. For Koppert, there’s very little that is scary or unfamiliar, and Rianne always responds quickly – even if she’s on holiday.’