Japanese knotweed is a perennial plant growing up to 3 m tall with strong, hollow stems. It has leathery, broad oval and tip pointed leaves with a truncated base. Leaves may reach a length of 12 cm and a width of 8 cm. The hairs on the undersides of the leaves are barely recognizable with the naked eye. The small white flowers appear in August.
Other invasive knotweeds that appear in Luxembourg are the giant knotweed (Fallopia sachalinensis) and the hybrid (Fallopia x bohemica).
The giant knotweed grows up to heights of 4 m. It usually has considerably larger leaves than the Japanese knotweed (up to 40 x 17 cm). Full-grown leaves have a heart-shaped base. The undersides of the leaves, especially the veins, are covered with clearly discernible hairs. The small flowers are white.
The hybrid between F. japonica and F. sachalinensis shows intermediate characteristics between both of its parent species.
Did you know?
Young shoots can be cooked like asparagus. Different sandwich spreads are produced from the plant.