A young shoot of knotweed is the peeping up in the grass in March. This plant is originally from Asia and is considered an exotic invader in the west. As such it is seen as a plague that is dangerous and damaging to local ecology and infrastructure.
Reynoutria japonica or Fallopia japonica or Polygonum cuspidatum are the scientific names of the species. Japanse Duizenknoop is the dutch name.
photo 2020 by Willem Velthoven for Mediamatic