Donkey rhubarb weed is island’s stubborn guest

By Nigel Baudains

Agricultural and environment advisor Andrew Casebow at Moulin Huet with Japanese knotweed, also know as Donkey Rhubarb. (Picture by Daniel Guerin, 0592294)

THE most invasive plant in Britain is threatening to smother the island. Japanese knotweed, or donkey rhubarb, was introduced to Britain from the Far East as an ornamental plant in 1825. It is currently found on more than 100 sites in Guernsey and is spreading quickly.

‘It can grow from just a single node and if someone cuts it and doesn’t dispose of it properly it grows again,’ said States agricultural and environment advisor Andrew Casebow.

The plant has enormously strong and deep roots which can penetrate concrete and go through walls. Japanese knotweed is not listed on the noxious weed ordinance as it flowers but does not re-seed. Mr Casebow said that the weed could be killed by cutting it back and injecting liquid into the hollow stems.

That requires equipment that could be costly and is mostly done by professionals. Few pesticides will kill it and States plant pathologist Terry Brokenshire is currently looking at which is the best.

‘A lot of people don’t like using pesticides and just keep cutting it back, but that won’t get rid of it,’ said Mr Casebow.

‘It’s a matter of cutting it back and treating the shoots each time they appear and it will eventually give up.’

He said it was important to dispose of cuttings appropriately and that they should not be composted or left on other pieces of land.

‘The remnants should either be burned or put in a sealed plastic bag so that they eventually rot down.

‘There is a strong need for control,’ said Mr Casebow.

‘The problem is mainly on privately-owned land, but also on States land.’

The plant is identified by red shoots which appear in spring with reddish-purple rolled-up leaves which unfurl to become lime green and later darken to mid green. It can grow by up to 10cm per day.

Cream-coloured flowers appear in late summer/early autumn and a mature plant can grow to three metres tall.

Article posted on 13th June, 2008 - 2.29pm

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