Baltic Garden - November 2012, VOL IV - VIPs Portal

10.3368/er.30.3.192 Ecological Rest. September 1, 2012 vol. 30 no. 3 192-199.
"Planting Native Species to Control Site Reinfestation by Japanese Knotweed (Fallopia
japonica)"
- by R. Howard Skinner, Martin van der Grinten and Art E. Gover. )
Biological control, practiced by native Blackberries
In the Baltic Garden, the native Blackberry has clasped its stems around the Japanese knotweed and
limited its ability to spread. The Blackberries even send vigorous stems up in the center of the Japanese
knotweed. See photos from the 9th December.
In contrast to Japanese knotweed, Blackberry retains its green leaves throughout the winter - and
therefore constitutes an important source of food for wildlife. The upper withered parts of Japanese
knotweed normally provide support for new shoots in the spring. BUT not this time. The plan is to remove
all stalks and cover the area with black plastic. Then roll out a thick layer of soil, with the possibility that
Blackberries can take root in it.
An alternative solution is to let the grass spread, so the area instead becomes an extension of the
garden-lawn.
As photo from 18th September shows, the Blackberries on their own are doing the arm wrestling with the
Japanese knotweed. There are no other plants to be seen in the frigid darkness, which the Japanese
knotweed creates during its summer growth.
The fact that Japanese knotweed shadows most other plants to death - has placed it on the list of 100
of the World's Worst Invasive Alien Species (the Global Invasive Species Database list -
www.issg.org/database/species/search.asp?st=100ss )