Can you Cover Knotweed with Tarmac or Concrete?

This is a collaborative post

Dealing with knotweed and considering options for covering it involves understanding the persistence and growth habits of this invasive plant species. 

Frankly, though the costs for the removal of knotweed may be high, it is likely the only option. The costs for removal of knotweed are here on the knotweeduk site. 

Here’s a summary of considerations for each option:

Tarmac

• Pros: Tarmac (asphalt) is a flexible surface that can be easier and less expensive to install than concrete. It provides a smooth surface suitable for many applications.
• Cons: Like AstroTurf and concrete, tarmac can also be penetrated by knotweed over time. The flexibility of tarmac means it might not offer as robust a barrier as concrete. Maintenance issues can arise if knotweed breaks through, requiring patching or resurfacing.

AstroTurf

• Pros: AstroTurf (synthetic grass) can provide an immediate aesthetic solution and is relatively easy to install. It can create a usable surface over areas where knotweed is present.
• Cons: Knotweed is known for its vigorous growth and can push through surfaces. There’s a risk that knotweed could penetrate the AstroTurf over time, damaging the integrity of the installation. Additionally, covering knotweed with AstroTurf does not address the root problem and may inhibit access for treatment.

Concrete

• Pros: Concrete offers a more durable barrier to knotweed compared to AstroTurf. If properly installed with sufficient depth and reinforcement, it can potentially prevent knotweed shoots from penetrating the surface.
• Cons: Concrete does not kill the knotweed; it merely attempts to contain it. The roots of knotweed can extend deep into the ground, and if the concrete does not go deep enough, the plant may find a way around the edges. Additionally, laying concrete is more permanent and disruptive, and if knotweed does breach the surface, repairing the concrete can be costly.

General Considerations

• Treatment First: It’s generally recommended to treat knotweed with appropriate herbicides or through professional removal before attempting to cover it. Knotweed’s ability to grow through various barriers can make management difficult if not properly addressed first.
• Legal and Environmental Considerations: In some regions, there are legal obligations to control and prevent the spread of knotweed. Failure to manage it properly can lead to legal consequences. Environmental considerations should also be taken into account, as knotweed can damage local ecosystems.

Conclusion

While it is technically possible to cover knotweed with AstroTurf, concrete, or tarmac, these measures should not be considered long-term solutions to knotweed infestation without first addressing the knotweed itself through appropriate treatment or removal methods. Professional advice from a pest control or landscaping expert familiar with knotweed is strongly recommended to devise a comprehensive management strategy.