The local residual materials come from nature reserves in the Netherlands, such as the Weerribben in Overijssel. So 100% local. This results in a considerably lower environmental burden than, for example, materials from other continents, which cause a considerable CO2 emission due to their transport.
The reed is purchased from thatchers as secondary reed. Secondary means that it can no longer be used for roofs; too short, too bent, etc. But it is an excellent raw material for road signs.