In 2005, the Groenewegen brothers and other Colours of Nature members made the switch from stone wool slabs to Grodan Grocube in pots. The small, airy stone wool cubes for ornamental crops in pots and beds worked well. Six years later, the stone wool manufacturers from Roermond introduced Grodan Grofit, which was especially developed for gerbera cultivation. It consists of the tried-and-tested GroCube cubes covered by a 2 cm thick stone wool disk c, offering the plant more firmness during harvesting. Part of the new substrate concept was that it was offered ready-to-use in pots according to customer specifications.
“We noticed right away that we had to add more water”, says the Westland grower, looking back. “As it transpired, Grodan's potting company in Breda filled the pots using a slightly different method than we were used to. Because our colleagues were experiencing the same problem and we bought the substrate as an association, we raised the issue with the supplier as Colours of Nature”.
Following some firm negotiation, things went well. The group of growers visited Breda a few times prior to the start of the second season to come to the right arrangement with the potting line team. It quickly turned out that the cubes had to be pressed a little harder, meaning that more cubes fitted into the same volume. “This resulted in a higher buffer capacity, meaning that we could better control the drip frequency and drain volume”, summarises Groenewegen. “In the next crop, we saw that after a few months, the leak had been plugged and that Grofit was doing a great job. The stone wool disk gives the substrate added value; it seals off the upper edge of the pot nicely, meaning the plant is firmly supported during harvest”.