Efforts by Dutch horticulturalists to commercially grow vanilla have failed, news website RTLZ said on Thursday.

Scientists at Wageningen University have been experimenting with growing vanilla since 2012 and in 2016 the private sector and outside investors became involved.

In total, €350,000 was pumped into the project, half from public sources, but it has proved impossible to grow the the flavouring without financial help, RTLZ said.

The last pods will be harvested this October. Vanilla is a slow-growing plant and it takes three years to produce pods.

Vanilla is one of the most expensive spices in the world, with a kilo costing around €550. Some 90% comes from the island of Madagascar and the trade is in the hands of a few powerful families.

The high price was one reason why Wageningen researchers began their experiment to assess how many pods can be harvested from a plant grown in a Dutch greenhouse and what is the cost.

‘We have managed to get the vanilla plans to flower and produce pods but I can’t guarantee the harvest and that is necessary to make a good business case,’ researcher Filip van Noort told RTLZ.