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Japanese Knotweed

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#1 Knights Hiller

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Posted 23 August 2006 - 11:30 AM

As a West Norwooder with a Japanese Knotweed problem, I thought I'd attach a useful link on how to rid yourself of this menacing weed:


Is anyone else suffering from this as I see plenty of it around on the train to Victoria?

This what the Environment Agency say about it...

Japanese Knotweed was introduced to the UK as an ornamental plant during the 1800s. It is commonly found today along railway lines, riverbanks, roads and footpaths, in graveyards, on derelict sites or anywhere that it has been dumped, dropped or deposited.

Japanese Knotweed forms dense clumps up to three metres in height. It has large, oval green leaves and a stem that is hollow and similar to bamboo. Usually in early spring (although it can be later in the year) the plant produces fleshy red tinged shoots. These can reach a height of 1.5 metres by May and three metres by June.

This plant can grow as much as 2 cms per day and will grow in any type of soil, no matter how poor. Towards the end of August clusters of cream flowers develop and then produce seeds that are sterile. The plant dies back between September and November.

Beneath any stand of Japanese Knotweed will exist an extensive underground root (rhizome) network that can extend several metres around and beneath depending on ground conditions. The spread of the plant is vegetative, ie all new plants are created by fragments of existing plants. A fragment of root as small as 0.8 grams can grow to form a new plant.

Japanese Knotweed grows pretty much anywhere, from field edges to sand dunes, through asphalt and out of lamp-posts. The speed with which it has spread to all parts of the UK has been spectacular when you consider that it does not leave seeds behind but grows from pieces of the plant or root system that are cut and transported by people or by water.

Because Japanese Knotweed does not originate in the UK, its does not compete fairly with our native species and is able to spread unchecked. Once established, Japanese Knotweed shades out native plants by producing a dense canopy of leaves early in the growing season. Although Japanese Knotweed is not toxic to humans, animals or other plants, it offers a poor habitat for native insects, birds and mammals.

Under the Wildlife and Countryside Act 1981 / Wildlife (Northern Ireland) Order 1985 it is an offence ‘to plant or otherwise encourage’ the growth of Japanese Knotweed. This could include cutting the plant or roots and disturbing surrounding soil if not correctly managed.

Edited by Knights Hiller, 23 August 2006 - 11:37 AM.

#2 lucysmith



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Posted 23 August 2006 - 11:44 AM

Our next door neighbour's front garden has this and luckily we haven't had it spread to our garden yet. The problem is that the house is owned by South London Family Housing Association and noone will take responsibility for maintaining the gardens. Only on two occasions once a year have the maintenance men come to strim the entire front garden.

#3 iclipper


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Posted 23 August 2006 - 01:46 PM

Sadly my garden is not so exotic - I suffer from good old fashioned bindweed. Any hints/tips on how to remove it from the lawn in particular?

#4 Sylvester



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Posted 23 August 2006 - 02:55 PM

This stuff is a menace! It is rampant in the parkland behind our garden and of course the roots run underground and under the fence. All we can do is dig it out whenever it pops up its ugly head. We noticed it growing unchecked around Lake Bled when we were in Slovenia this summer, so I guess it is a Europe-wide problem.

I think we have discussed this topic before?

Bindweed is also a pesky plant which needs to be dug out. That doesn't do your lawn much good though.
aka Pie

#5 elleme



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Posted 23 August 2006 - 03:22 PM

I don't have any Japanese Knotweed but it's probably only a matter of time as I've seen it in a road nearby. I got a London Wildlife trust mag through the post a little while ago and was surprised to learn that Japanese knotweed and another notoriously vigorous plant, Russian vine, have hybridised to produce a new plant. They first found it on just one nature reserve in North London (they have called it Haringey knotweed!) Apparently it doesn't share the thuggish tendencies of its parents, which is perhaps just as well or it would take over the whole world. It's fascinating how that happens.

I have some bindweed and I've lessened it considerably but not entirely eradicated it yet. Most of mine was in the borders on the edge of my garden, rather than the lawn. I did my best to dig out every scrap of root when I could find some, applied paint-on glysophate (I won't normally use it but it was really bad when I first moved here). In a lawn I can understand you might not want to dig it up. I wonder if a flame-weeder would help?

#6 Knights Hiller

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Posted 23 August 2006 - 09:01 PM

My neighbour users the 'flame-weeder' approach. Not only does she find it great fun, it also appears to work.

Definitely something to consider doing after a stressful day at work. :)

#7 Axean



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Posted 24 August 2006 - 03:29 PM

I think they can sell the paint-on version of Glyphosate in the Hollybush Hardware store. Its difficult to find in many diy shops. The spray is better for the other evil root spreading weed, mares tail. If the roots of bindweed are only in your gardern you can kill it off by ripping it out a few times. Knotweed and Marestail must be poisoned. Digging out the roots is almost impossible.