About to build a pumptrack on area that has knotweed problem...advice needed.

Capra

Hi, I'm going to build a pumptrack in a disused haggard near my house. This area has always got very heavily overgrown by Japanese Knotweed. You would have to hack your way through it. We sprayed it last September and there is currently very little fresh growth. I was able to walk around in there quite easily last week. Now, i cannot remember the growing pattern of knotweed, so is there only little growth because its the wrong time of year or has the spraying we did last september killed it off for this year? There are a few plants growing that were probably missed.

Obviously with this project there would be a lot of ground disruption. I'm keen to start on the project asap but I'd prefer know what precautions I should take before I do anything.

macraignil

Capra wrote: »

Hi, I'm going to build a pumptrack in a disused haggard near my house. This area has always got very heavily overgrown by Japanese Knotweed. You would have to hack your way through it. We sprayed it last September and there is currently very little fresh growth. I was able to walk around in there quite easily last week. Now, i cannot remember the growing pattern of knotweed, so is there only little growth because its the wrong time of year or has the spraying we did last september killed it off for this year? There are a few plants growing that were probably missed.

Obviously with this project there would be a lot of ground disruption. I'm keen to start on the project asap but I'd prefer know what precautions I should take before I do anything.

Japanese knotweed that I pass on the road is actively growing at the moment. If you are saying there are a few knotweed plants growing then the knotweed is still alive in your plot. From what I have read it continues to survive in the ground even after treatment with weed killer and usually takes years of repeated treatments to be fully eliminated. Ground disturbance is likely to spread the underground parts of the knotweed and you should be carefull where you move the soil as it is very likely to bring some of the knotweed with it.

Alkers

Be very careful! I think it can remain dormant for over five years and then regrow, even through concrete.
If you sprayed it, I wouldn't be at all confident that you have been effective in getting rid of it. In my experience, the most effective way of controlling it is injecting it but this needs to be repeated each year and is very time consuming!

From a quick google search as I'm not in work:
When dealing with Japanese Knotweed it is more of a case of what not to do…

• Do not strim, cut, flail or chip the plants as tiny fragment can regenerate new plants and make the infestation harder to control
• Do not attempt to dig out Japanese Knotweed, this can actually encourage the plant into growing faster, therefore colonising an area more aggressively
• Do not move or dump soil which may contain plant material as this may also add to its spread.
• Do not attempt to pull the plant out of the ground, as this can expose part of the infectious crowns, stimulating growth
• Do not use unlicensed herbicides close to any watercourses, plants or wildlife
• Do not compost any part of the plant as due to the resilient nature of knotweed it could survive and grow on when the compost is ready for use
• Do not dispose of Japanese Knotweed in garden waste allotments as this just transport the plant to new locations
• Do not spread any soil that has been contaminated with Japanese Knotweed rhizome as new plants will sprout

Do not do break the law – Remember it is an offence if you cause the spread of Japanese Knotweed either intentionally or unintentionally.

Day Lewin

It can regenerate from an inch of root. (3 cms)

So do not move the soil!! And do not dump clippings or prunings, even if you think they are dead.

If most of it died from your spraying last year, then another spraying this year should take care of things: but keep a vigilant eye, on every little bit. This stuff has an awe-inspiring power to grow despite all obstacles.

magicbastarder

it's also not clear whether the land is yours or not, so tread carefully.

Capra

The land is mine so no issues there. Its a very enclosed area and has never spread outside of the haggard. Trees on two sides and old dilapidated farm buildings on the other. Would I be better off leaving the ground undisturbed and just getting fresh clay in and dumping it on top rather than uprooting more and more of these plants?

my3cents

Digging up roots is about the last thing you want to be doing.

However one technique used is to bund the soil the roots are in and cover it in an impenetrable geotextile. You still have the problem of cleaning up any machinery used.

You mentioned a haggard so if this is a farm do you have access to machinery? Another option is burying the roots but they really need to go down 2 meters.

You can't do much to make it worse where it is growing already but its spreading the JK that is the real problem. You'd easily stick a big enough bit to a bike wheel to spread it. All it needs is a finger nail sized bit of root.