A typical road sign, as they can be found all around the Netherlands. Eelde Airport is shown as *✈ Groningen*. The tree just behind the sign is a Silver Birch (/Betula pendula/), suffering from witch's brooms. This deformity is caused by a fungus called /Taphrina betulina/ or /Exoascus betulini/, and has the effect that branches start to branch excessively. Many birch trees in the Netherlands can be seen with witch's brooms.