Japanese knotweed
Japanese knotweed (JDK) is found in many places in Nuenen. This invasive plant spreads easily: even a small piece of root or stem (with nodes) is enough for it to grow again. The locations and areas where the plant occurs in our municipality are now known and have been posted on Map .
Rapid growth and displacement of other plants
Japanese knotweed is not poisonous, but it does pose a threat to biodiversity. Because it grows so quickly, it crowds out other plants. The plant also spreads underground: its roots can extend over long distances (2–3 meters). Since Japanese knotweed does not reproduce via seeds, its flowering does not in itself pose an additional risk.
No legal control obligation, but municipal commitment
There is no national requirement to control the plant. However, there is a ban on the sale and distribution of the plant and plant material. The municipality of Nuenen is actively working to limit the nuisance and prevent further spread.
Current approach in collaboration with experts
The municipality began injecting the stems of Japanese knotweed in late 2024. In 2025, this treatment was repeated at several locations within the municipality, including new ones. This year, Japanese knotweed is being monitored again to determine whether both the area covered and the number of plants have decreased.
This method was chosen because it is currently one of the most effective treatment methods when the stems are thick enough. For the treatment to be effective, there must be a sufficient number of large stems. That is why we let the plant grow first. The stems are injected once between late August and early September. This is the best time of year because the sap flow is directed toward the roots at that time, which makes the treatment more effective.
Japanese knotweed does not disappear in a single year. By repeating the treatment, the plant is suppressed and kept under control. The goal is to prevent it from spreading further.
Report
Do you see Japanese knotweed in public areas? Please report it to us.
Recognizing Japanese knotweed
- The foliage is fresh green.
- In spring, the stems have red veins.
- From August to October, the plant has white flowers.
- The leaves alternate on the stem.
- The stems are covered with red spots.
- The stem is hollow inside.
- The plant is a large bunch with stems emerging from the ground.
- The roots are orange inside.
- From the root corm come white shoots resembling asparagus.
How can you identify knotweed in each season?
- Spring (March–May): The plant starts as red or purple shoots that grow rapidly, similar to asparagus. They have green, heart-shaped leaves and grow very quickly, reaching up to 1.5 meters by May.
- Summer (June–August): The stems are green with reddish spots and resemble bamboo. The leaves are oval, leathery, have a straight base (heart-shaped), and grow in a zigzag pattern along the stem.
- Fall (September–November): The plant blooms profusely with small, creamy-white flowers in panicles. The foliage often remains green until the first frost.
- Winter (December–February): The plant dies back above ground. The stems turn brown, dry out, and become hollow, but often remain standing throughout the winter.
You can read more about Japanese knotweed on the NVWAwebsite at .