Large-scale eradication of New Zealand pygmy weed Crassula helmsii from grazing marsh by inundation with seawater, Old Hall Marshes RSPB reserve, Essex, England

Published source details Charlton P.E., Gurney M. & Lyons G. (2010) Large-scale eradication of New Zealand pygmy weed Crassula helmsii from grazing marsh by inundation with seawater, Old Hall Marshes RSPB reserve, Essex, England. Conservation Evidence, 7, 130-133.
Share Tweet Email

This study is summarised as evidence for the following.

	Action	Category
	Crassula helmsii: Use salt water to kill plants Action Link

Crassula helmsii: Use salt water to kill plants

A replicated, controlled container trial and a small, replicated, before-and-after field trial in 2006–2009 at a grazing marsh in Essex, UK (Charlton et al. 2010) reported that flooding with seawater eradicated C. helmsii, although no statistical tests were carried out. In the container trial, C. helmsii turfs grown in seawater were described as ‘appeared to be dead’ after five months, but those in freshwater and brackish water were still growing. In the field trial no C. helmsii was observed at the end of the seawater flooding period nor 9-11 months after seawater was drained. In the container trials, 15 x 15 cm C. helmsii turfs were placed in 15 l containers and checked every 6-7 days. Four were covered with brackish water (2,000 μS electrical conductance), four with seawater (30,000 μS) and four with freshwater. Field trials were carried out at two sites reported as having ‘abundant and widespread’ C. helmsii. An 8 ha field and a 120 ha field were flooded with seawater to 5 cm above the usual winter water level from April 2006-January 2007 and January-December 2009 respectively. C. helmsii was surveyed between August 2007 and August 2010.