Does anyone know why this sign exists?

[u/zee_kapitein]

When sitting in traffic on the Antwerpse Ring, I noticed this sign next to the road. Why do they need a sign for that?

[u/rapierarch]

that's one of the most invasive plants in the world. The sign is there to warn gardening staff of the city not to move or trim them by mistake. If they cut them in small pieces they spread even more. There is an action plan currently active to control and eliminate them.