Wednesday, 10 March 2010

Japanese Knotweed, A tasty snack for Psyllids – we hope.

The news in the UK yesterday was as depressing as ever, Apart from the real news of disasters, wars and crime, it includes political ramblings (yawn), the Oscars (yawn again), and the tenth anniversary of the London Eye (where did those years go?).  One item did catch my eye, though.  Japanese knotweed was introduced into many countries as an ornamental plant in the 19th century – though no botanist seems to want to take credit for it. Now it is illegal in the UK to spread the dratted plant and is classified as controlled waste. It will burst through, tarmac, concrete and undermine buildings. 
There have even been cases where a mortgage has been refused where Japanese knotweed is found in the garden. It grows at the rate of more than a metre a month and its roots can go down 3 metres (9.8 ft). Herbicides need repeated applications over several years and the strongest of these have been withdrawn from sale because of health risks.

Now, for the first time, a biological control is to be tried – a tiny insect which, the scientists hope, will only eat the target plant. The UK lags behind other countries in introducing biological controls.  Australia, New Zealand, South Africa and the US have tackled 100 weeds between them with complete or partial success in half the programmes. Like most non-scientists, the idea of introducing another alien species makes me nervous but, if we don’t find an answer, it is estimated that the UK faces a cost of £13.5bn ($20.4bn; 15€) by the turn of the century (according to the BBC).

So chomp away, little psyllids, but please make sure to follow the diet recommended by the scientists.

On a more cheerful note, I walked over to All Souls Graveyard, where the nasty plant had almost obliterated everything except the trees, to see the current state of the site. I found that the Council’s efforts over the past few years have worked and the area is recovering. Local residents have planted bulbs and large clumps of snowdrops are thriving.  A good news story at last. Though it won't make the headlines.

The first photo is licensed under Wikipedia Commons Germany
The second one is 
licensed under  Wikipedia Commons Netherlands. It was taken at Beekbergen (The Netherlands). A few years ago, this place was still Knotweed-free 

1 comment:

  1. It's tasty for us too! Alot of people don't know you can eat and it's actually really nice. Try the recipe below and see what you think....

    Japanese Knotweed Crumble Recipe:

    500g young knotweed shoots, including leafy “spears”, lower sections peeled, sliced into 8cm pieces
    50ml water
    100g caster sugar
    200g plain flour, sifted
    100g cold butter, cubed
    125g brown sugar

    Thanks for sharing, very informative post!


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