Japanese knotweed problems

[Yog Sothoth 10]

Yeah it spreads by seeds and also by rooting of broken fragments. Its home in Japan has a similar temperate maritime climate as the UK so it likes it here. Unfortunately it has NO natural enemies here, so grows unchecked. Slightly sinister stuff, and I generally LIKE plants, even the other invader, giant hogweed!

Sodium chlorate weedkiller will kill it and sterilises the soil for 2-3 years afterwards, so NOTHING will grow. Drastic but effective. To tackle a big patch needs a lot of sodium chlorate though, which isn't cheap, and you'd probably get the police round thinking you had a bomb factory set up!

Any other removal method takes loads of time and hard work, even using paraquat or glyphosate, which have to be sprayed repeatedly over 2 years or even longer.

Funnily enough, the young shoots can be cooked and eaten like asparagus. Quite tasty apparently.

There is a massive epidemic and it's time Defra put some money into a nationwide effort to tackle the stuff. Leaving it to landowners or skint councils is never even going to make a dent, and eventually it'll be destroying our gardens, then invading our homes. Ordinary citizens can't devote the money, time or effort required to stop it and if it's on neighbouring land, it's just firefighting anyway, trying to keep it off your own land.

[szb100 10]

Just saw this and I'd like to mention that sometimes dealing with Japanese Knotweed is not the nightmare people make it out to be.

We had about 6 ft of the stuff coming through a retaining wall. After getting the people on the other side to spray weedkiller, we sprayed our side as well and after recurring treatments and a bit of persistence it hasn't yet come back.

Woo.

[Yog Sothoth 10]

That's reassuring to know. Unfortunately near us there's maybe 100sq.m of the stuff getting bigger every year. I'm going to blast it with sodium chlorate. Bare soil is better than an endless knotweed forest. Eventually ordinary weeds will colonise it anyway.

[szb100 10]

Glyphosate worked for us. If you break the stems and pour it down the hole it helps as well.

[I1L2T3 10]

4 In the patch of land adjacent to Holmhust road and behind KFC

 

It extends along the side of the stream on the other side of Holmhirst by the banks of the stream behind the Big Tree. Know somebody on Fraser Crescent and it has infiltrated their garden causing some minor structural damage to walls.

[muddycoffee 10]

Yes that stream is in quite a deep little valley, I expect that it makes the area well protected from frost during the winter which will prevent the weed from dying back so much in the winter.

It is areas like this that everyone in the city should really be concerned about. Because unchecked it will lead to everyone's property being threatened.

[Yog Sothoth 10]

Sheffield seems to be particularly bad for it. I come from Pudsey between Leeds and Bradford, and that area isn't nearly so badly infested. It's everywhere down here!

[Yog Sothoth 10]

Coming back to this, does anybody know what's the best time of year to spray the stuff? I've been slashing it down and using sodium chlorate on it, but it struck me that it might be better to spray its young growth in spring, when it's only a foot or two high, and after it's used up some of its reserves overwintering.

[TimmyR 10]

don't get it mixed up with bind weed. That is fairly similar in appearance but far less aggresive.

[Yog Sothoth 10]

No, I know bindweed (Calystegia?). This is 12 feet tall, 2" thick, unmistakeable. Evil.

[cressida 1,571]

one of my neighbours, has just come round, her garden is behind ours, and has told me that the plant which buds little white flowers is growing in her garden, it seems it has been planted by my next door neighbour and is growing up the trees, but the danger is from the roots thtat spread underneath to the houses, please don't tell me any negatives I can imagine, but if anyone has had the problem and knows how to cope with it please reply

[billyhill 10]

Info from Env Agency

 

The most effective active ingredient for use on Japanese Knotweed is called Glyphosate. This is the active ingredient found in 'Round Up' and other similar herbicides. It is effective on Japanese Knotweed even though it does not kill the plant immediately. Instead, the herbicide soaks through the leaves and is taken into the plant root system. The greater the number of green leaves present, the larger the quantity of herbicide that can be absorbed into the plant. It can take up to ten days for the plant to begin to die off after treatment and you should always watch for regrowth.

 

A quicker method of removing Japanese Knotweed involves the clearing of above ground leaf/stem material and the removal of ground material polluted with roots. Care should be taken to ensure that all Japanese Knotweed roots are removed - this is one situation where it pays to remove too much material.

 

Even with great care, a certain amount of regrowth in the spring would be expected and any should be treated with an appropriate herbicide as discussed above. Make sure you read on for tips on how to prevent spreading Knotweed fragments around the site during the works.