ELF Trust, Harewood, Calstock

Japanese Knotweed Removal
2002/2010


Removal of Japanese Knotweed on land managed by the ELF trust

The sites are situated on the Cornish (western) bank of the River Tamar, 500 meters west and 700 metres north-east of O.S. Grid Ref: 452690. There were initially three growths along the river bank (map to follow).

Picture of Japanese Knotweed

It is difficult removing the roots of Japanese Knotweed as the roots can reach a depth of 7 metres.
Each remaining peice of root or rhizome, as small as 1cm, can produce new growth.


Site 2: This is the major area some 10 by 6 metres, abreast the bund, from river to drainage ditch. Data for this below and updates on the web log.

Site 6: In 2002 one plant was discovered and only noticed again in 2004. Since then there has been no regrowth..

Site 9E: (now D) This small patch was right on the river edge, and grew back only in the year of discovery, 2002. There has been no regrowth to date.


Site 2: 2008

The very high tide this winter breached the bund and washed away my stash of old rhizomes and stems etc. I found the bags and hopefully most of the bits ( as if ). -:- 12th May Found 8 rhizomes growing in drainage ditch :(.

The first pull was completed on 18th May. See  summary and/or download details. 



From 2007 counting will be used for Site 2 rather than the previous estimate.

Site 2: 2007

The number in brackets denotes the amount of growths pulled, compared to estimated growth at the time.
    April 28th : 807 (60% of site)
    May 8th : 701 (regrowth and remaining 40%)
    June 16th : 206 (40% of site) regrowth much smaller here than other.
    Aug 27th : 308 (75% of site). Was worried about the long gap since last pulling, but growth overall was very little. The main growth was in the area least pulled i.e the centre by the drain. There are many other plants competeing now and most of the site is covered in other species.

The idea of leaving a small patch is that if the root structure is one rhizome then maybe the remaining part with above ground growth will draw energy from other parts of the rhizome and deplete its energy. Well I don't know if that is happening but it looks that way.
    Total : 2022 (Aug 27th)



Site 2: 2003


Site 6 and 9E: 2003

Site 9E

Site 6


Site 6 and 9E: 2002


 Summary 

Sites 2002 2003 2004 2005 2006 2007 2008 2009 2010
(see Notes) 1000's 1000's 1000's 1000's 1000's 2022 1157 1227 1474?
(see Notes) 1 0 1 0 0 0 0 0 0
(see Notes) 10 (45) 0 0 0 0 0 0 0 0

 Download 2002 to 2012 Details   Download 2008 to 2102 Details 


Last Updated 6th July, 2018