Knotweed is pretty horrific to homeowners. In the UK specifically, it seems that you can be liable for damage to neighboring properties done by knotweed on you

Knotweed is pretty horrific to homeowners. In the UK specifically, it seems that you can be liable for damage to neighboring properties done by knotweed on your land. Similar to the land a gas station was built on, its value can be negative due to the cost of cleanup. For knotweed, that's a 20 foot deep hole several times larger than the visible infestation, and in the UK, you can't cart the soil somewhere, you need to sterilize it and bury it in place. Since the rhizomes spread everywhere, tens of meters laterally, an infected house is the sign of an infected neighborhood, any cleanup must be coordinated to be effective.