The Japanese knotweed growing season has drawn to a close and the plant’s above-ground growth has now mostly died back. But despite looking dead, knotweed will be replenished with new energy reserves from the summer growth which are drawn down and stored in its powerful underground rhizome system, ready to re-emerge stronger next spring.
After the first frost, knotweed’s heart-shaped leaves turn yellow and fall to the ground. Its bamboo-like canes lose their green appearance and start to turn brown and brittle – although most will remain standing. The distinctive crown will still be visible, but no fresh growth will appear until the ground begins to warm in the spring, usually around March or April. Check out our ID Guide for pictures of knotweed in winter.
Homebuyers should be especially vigilant when viewing properties during the winter months, when property owners looking to sell may be tempted to take advantage of the plant’s hibernation which makes it much easier to conceal. Failure by the seller to disclose the presence of knotweed could lead to a costly legal claim for misrepresentation when the plant regrows.
Herbicide treatment cannot be carried out during the winter months since it requires the plant to be in leaf in order to effectively absorb the chemicals. But that doesn’t mean knotweed should be left until spring.
There are very efficient, cost-effective solutions that can be undertaken through the autumn and winter months with excellent results.