The underground rhizomes of this species can penetrate loose aggregate and grow through existing small cracks, openings or voids in asphalt/concrete. Like many plant species, once established, the underground structures of Japanese Knotweed rhizome can slowly increase in volume over time and ultimately impact built structures (e.g. drains and patios), typically in the form of exacerbating existing weakness or damage.
The species’ fast vertical growth rate allows it to outcompete much of the native vegetation in the UK and Ireland.
Other negative impacts include:
- Loss of biodiversity.
Increased flooding risk by impeding river-water flow.
- Increased riverbank erosion.
- Economic loss, primarily associated with control costs in the construction sector.
- Delays to development.
- Aesthetic damage to gardens and landscaping.
Loss of amenity and recreational space.
- Adverse publicity for landowners.