Sorry or any confusion, Genie- Liz and I were referring to the Japanese knotweed she mentioned here:

"Subject: RE: BS: Pussy willow branches to find homes for
From: Liz the Squeak - PM
Date: 08 Mar 09 - 04:22 AM

Same goes in the UK - there are several plants that cannot be planted due to their invasive growth and ability to adapt. One such plant is the Japanese knotweed... "

maeve