Japanese Knotweed

(from Wikipedia) Japanese Knotweed is listed by the World Conservation Union as one of the world’s worst invasive species. The invasive root system and strong growth can damage concrete foundations, buildings, flood defenses, roads, paving, retaining walls and architectural sites. It can also reduce the capacity of channels in flood defenses to carry water.

The success of the species has been partially attributed to its tolerance of a very wide range of soil types, pH and salinity. Its rhizomes can survive temperatures of −35 °C (−31 °F) and can extend 7 metres (23 ft) horizontally and 3 metres (9.8 ft) deep, making removal by excavation extremely difficult.

The plant is also resilient to cutting, vigorously resprouting from the roots. The most effective method of control is by herbicide application close to the flowering stage in late summer or autumn Some home owners in the United Kingdom are unable to sell their homes if there is any evidence of knotweed on the property.

According to the UK government, the cost of controlling knotweed has hit $3 billion. It cost $130 million to eradicate knotweed on a patch of land on the site of London’s 2012 Olympic Games velodrome and aquatic centre. Defra’s Review of Non-native Species Policy states that a national eradication program would be prohibitively expensive at £1.56 billion.