Jap.knotweed

[daveatdave]

22 hours ago, topchippyles said:

Only way I have seen is to dig down deep and remove the hole area 

you need to go at least 20 ft down 

[openspaceman]

14 hours ago, Grassyass said:

If you leave it until the autumn it will have dropped all it seed heads and they will grow back again, In our experience it takes about 5 years to get rid of it , we do the stem injection as well as spraying  ,but the sooner you treat it the better , 

The old folk ditty was:

 

"one year's seeding, nine years weeding"

[Paul in the woods]

Its my understanding that Japanese knotweed doesn't produce viable seed in the UK currently, apart from the rare occasion it hybridizes with Russian vine, so you don't need to worry about the seed.

[Chris at eden]

16 minutes ago, Paul in the woods said:

Its my understanding that Japanese knotweed doesn't produce viable seed in the UK currently, apart from the rare occasion it hybridizes with Russian vine, so you don't need to worry about the seed.

That is my understanding as well. All the plants in the uk are female apparently. 

[Trailoftears]

Timing is an interesting question.I've always aimed for catching plants on their way up/growing strongly re:application with glyphosate.My theory being-

A:the plants are growing strongly and accordingly will absorb/translocate the herbicide more effectively.

B:The tissue being attacked is softer/younger and therefore more vulnerable to herb.app (+you need to apply less volume and closer to the ground),which is safer for you and better for the environment.But apparently, regarding J.Knotweed and also bracken-and possibly other 'difficult species' too-brambles?

The sweet spot is when they approach the max height/senescence.Which I find really surprising given they are presumably pretty much 'standing still' at that point in their annual growth cycle.I can see that that point would give you max leaf volume to attack,but also much harder to apply effectively given the height and density of a 6'x6' stand of knotweed?Another reason I guess is that you have to consider the insect/bee population should you spray in conjunction with flowers on.

[Trailoftears]

I recently took out via a bladed bruschcutter a stand of say,3 sq.metres of knotweed immediately nxt to the riverbank on the flat With a view to future spray app..Then I discovered it was growing right down the stony/undercut bank virtually into the water.Dealt with that the best I could (wet feet) fascinating tho to notice that big lumps of rhizome are literally hanging in the air over the water waiting for gravity or a flood/local riverbank collapse to drop lumps into the water and away they go.

[Peasgood]

18 hours ago, Spruce Pirate said:

Quite a while ago we used to spray it with glyphosate in Round-Up form.  It always seemed to shrug it off unless sprayed later in the year when it went into effervescence.  Never seemed to have much effect when sprayed earlier in the year so interested to hear different stories of how to treat.   Haven't done it in years, but do have a wee bit to treat now so I might try hitting it early. 

Senescence is the word you were looking for.

[openspaceman]

3 hours ago, Trailoftears said:

The sweet spot is when they approach the max height/senescence

Yes that is for maximum translocation in order to kill the rhizomes. Trouble is that by this stage the bracken has completely shaded out any heathland species and it then has some sort of allelopathic effect that prevents other species germinating. Clumps expand by 8ft a year because the rhizomes continue to extend all the time the soil remains warm enough.

 

Okay with grassland you can kill everything and reseed  but on heathland conservation we have several dilemmas, A lot here is SSSI and the powers that be forbid any work March to September, because of bird nesting. The result is an overall loss of heather, tufted grasses etc. The net effect is to diminish the habitat that the birds breed in.

 

IMO a triage system is needed, those bits of wall to wall bracken need treating (and I prefer cultural methods and carting off site), those bits with no bracken by June should not be walked through and  then  you have the bits in between that just need the bracken stems cut below the lowest frond while the stem is still soft.  Here the aim is to stop bracken forming a canopy.

 

 

BTW I was unaware that JKW did not set viable seed, of course himalayan balsam the other big invader does. The specification for burying soil contaminated with JKW on a big development was to bury it in plastic lined cells 4 metre deep, I never liked that but we knew the smallest piece of the plant was able to produce viable growth.

[Trailoftears]

Fascinating.I'm surprised there's no market that I know of for bracken compost bagged up.The Acid-loving plants dream medium I would imagine.Highly regarded for blueberry cultivation I gather.Back in the days on upland Welsh hill farms they would cut/dry and haul down bracken to litter under the animals all winter.Unlike straw,it cost nowt and there was plenty of it!Politically incorrect now,but the same applied to peat too-trench,cut,stook it to dry,hauled down from the hills and re-dried on the zinc roofs.Would pretty much keep them warm thru the Winter plus they couldn't afford coal in those pre-grant days.Probably the hardest work I've ever done!

[Spruce Pirate]

4 hours ago, Peasgood said:

Senescence is the word you were looking for.

 

Quite possibly.  I'm only blindly repeating what I was told, thought it was to do with the shimmer on the end of the leaves at that time of year.  I've never heard of senescence before, but I've looked it up.  Every day is a school day!