Ben Lindley, Company Director at Japanese Knotweed Ltd. Last reviewed on 10th January 2026.
Can knotweed survive freezing weather?
What happens to knotweed in freezing temperatures? In this article we explore the effects of sub-zero temperatures on knotweed. When temperatures drop below zero a lot of plants die completely, meaning they become unviable for regrowth when the weather warms. So what happens to Japanese knotweed? Well, it does not die off in freezing temperatures – but it does change how it appears.
- Above ground growth dies back
Frost and freezing temperatures kill the visible stems and leaves. They turn brown, brittle, and collapse. - The plant goes dormant underground
The rhizome (root system) remains alive and viable below ground, even in prolonged freezing conditions. - Freezing does NOT kill the rhizome
Knotweed rhizomes can survive severe winters, including sustained sub-zero temperatures. - Regrowth occurs in spring
Once temperatures rise, new shoots emerge – often earlier than many native plants.
Why this matters for property owners
- Knotweed is still present in winter, even if you can’t see it.
- Dormant knotweed can be missed during surveys if not carried out by an experienced surveyor.
- Ground disturbance during winter can spread the rhizome, making the problem worse.
- Treatment planning should continue year-round — winter is often used for excavation or management planning.
Key takeaway
Frost kills the visible growth, not the plant itself.
Japanese knotweed survives underground and will return when conditions improve – as the image below shows knotweed recovering in the spring from frost damage.
Can Japanese knotweed be surveyed in winter?
Yes – but with limitations.
An experienced knotweed surveyor can still identify:
- Old canes and leaf litter
- Disturbed ground patterns
- Historical evidence of growth
- Rhizome spread risk areas
However:
- Dormant knotweed is easier to miss
- Surveys rely more heavily on experience and site context
- Findings often include precautionary buffer zones
Winter surveys are common for construction and due diligence, but should be carried out by a PCA-qualified surveyor.
Why are winter works considered high risk on development sites?
Winter is a high-risk period because:
- Knotweed is invisible above ground
- Soil movement can spread rhizomes unknowingly
- Contaminated soil may be removed or reused illegally
- Discovery mid-project can cause costly delays and redesigns
This is why best practice is to:
- Survey before ground disturbance
- Clearly mark exclusion zones
- Implement a Knotweed Management Plan
- Use a Watching Brief during enabling works
Getting rid of knotweed
- Spring to early autumn (April–October) is the most effective period for herbicide treatment, when knotweed is actively growing and drawing nutrients back into the rhizome.
- Late summer / early autumn is often the most effective window for long-term control
- Multiple growing seasons are usually required for complete control
- Treatment plans typically run 3-5 years, depending on infestation size and method
- Winter offers a good window for removal: Winter can be a good time for mechanical excavation and physical removal of the root system, as the lack of above-ground foliage makes the area clearer and the ground condition can facilitate access.
Conclusion
Knotweed doesn’t disappear in winter – it hides.
Early identification and planning protect budgets, programmes, and compliance. Get ahead of knotweed growth season and book an early spring survey.