Thursday 31 August 2017

Speedy elimination of Japanese knotweed and equisetum?

Stump application of glyphosate to hollow stemmed herbaceous plants

Hollow stems here
I have always dismissed direct application of herbicide to stem bases of herbaceous plants. Use of translocated herbicide on unwanted tree stumps is a well accepted and successful arboricultural practice. I now think it might work on some herbaceous plants too. I am not being original and this notion has always been floating at the back of the literature in a kind of anecdotal way.

I shall call it JKW today
Today I offer two case studies. One I repeat from my earlier post when scientist Peter Williams used an injection technique wth an Autumn treatment on well established Japanese knotweed in his daughter’s garden. He completely killed it in one go. I take this as proof of principle that very strong glyphosate applied internally works very well. It is not quite the same as cutting the plant back and drenching strong herbicide down the hollow stems but it does depend on a very similar principle.
My other case study is my own experience in Bolton Percy cemetery where I have completely killed a huge clump of an ornamental variety of mares tail Equisetum hyemale in a similar six month period from a single Autumn application. I have no reason to think that this equisetum is fundamentally easier to control than the regular weed Equisetum arvense; the only difference is that its hollow stems are wider.

I also submit the anecdotal evidence provided by one of my readers. My post on control of Japanese knotweed (JKW) has been outstandingly popular and has been read 40,000 times and seems to be used as some kind of unbiased forum on this much feared and overhyped weed. So too, dare I say it, has my post on mares tail that boasts almost a hundred comments. Reader ‘anonymous’ claims complete success when in late Summer he cut back his eight foot high JKW to about 15inches and completely killed it with very strong glyphosate dribbled down into its 2 cm thick hollow stems.

The weed needs to have its root system intact
I am personally much more familiar with spraying the necessarily well developed foliage of difficult weeds such as ground elder, couch grass, bindweed, mares tail and JKW. A large leaf area is needed to drink up the weedkiller and translocate it back to the complete root system. The roots must be intact and if the gardener has previously tried to chop out the weed he will fail or at least take very much longer. Roots will not be attached to the tops and sprouting broken roots will be at several different and un-responsive stages of development. In the case of mares tail the translocated weedkiller needs to go as far as six foot down. In the case of couch it needs to translocate horizontally a long way along attached rhizomes. 
Sometimes the advantages of an intact root are more subtle. In my post about eliminating ground elder repeated spraying was done over a three year period. The beauty of an intact root was that the reviving ground elder shoots over that period appeared more or less in the same place. This enabled me to use a strategy of opportunistically planting in any spaces from the second season. Where ground elder has been previously chopped and the soil has been worked it come up all over the place and tiny pieces infiltrate between the roots of perennial plants in such a way that you will never be rid of it.
The need for intact roots is exactly the same with cut back ‘hollow stem weeds’. A heavy topped clump is beheaded and the roots must not be disturbed.
It is of course totally useless to apply glyphosate to the soil.

Strength of glyphosate
When normally spraying there are several reasons why it is best for maximum efficiency to use glyphosate at the recommended rate. My normal rate is 1:50 of commercial 360gm product. I sometimes go down to 1:100 and for very difficult weeds such as equisetum as strong as 1:30. Some weedkillers lose their efficiency if used too strong. This is not my own experience with glyphosate - even although some sources say so.
Although Peter’s injection of JKW applied only a very small amount of glyphosate he did use his professional product neat. My own drenching technique on the equisetum stumps was 1:15
If you are using amateur sources of glyphosate the concentrate is usually much weaker and you need to adjust your calculation.

Case 1 Stem injection
You can read about how Peter Williams spent a happy hour in eliminating a small patch of his daughter’s knotweed in my previous JKW post. Today I will more or less  merely repeat the pictures. No trace of the knotweed ever returned. I did ask Peter what he would do if he had had a quarter acre of it as I had had in Worsbrough cemetery. He said he would spray because injection would be too fiddly. I do wonder however considering the exorbitant costs charged by cowboys whether even with thousands of ten foot stems it might have been worthwhile.
Had I my time over again I think I would have tried cutting back a sample (with my hedge trimmer) and dousing the stumps (with my knapsack sprayer) using very strong glyphosate

JKW is quite woody by Autumn
You can cobble an injection gadget together or find one on the net
After a single injection JKW has never been seen again
Case 2 Spraying cut back equisetum
It threatened to take over
I like the ornamental mares tail Equisetum hyemale although it does seem to grow with the same vigour as the common weed and given several years without competition from other strong vegetation builds up the same strong deep root resource. Such a root system will sustain new growth over many years of persistent weeding.
I had planted Equisetum hyemale fifteen years ago in Bolton Percy cemetery, confident that with my spraying techniques I could contain it. I can. But I had not bothered and it had made a strong and dense four square metre clump. I do not want my legacy to be an overgrown cemetery and last Autumn decided to eliminate it.
Equisetum is notorious for its silicon fortified surfaces shedding any herbicide spray. With Peter’s injection technique still in my head I must have read somewhere about stump application. I decided to try it!

The hedge trimmer does a very good job
I cut the clump back completely to the ground last September using my hedge trimmer. I made up a few litres of a strong 1:15 (ish) glyphosate solution in my knapsack and with nozzle pointed downward and almost touching doused the stump clump heavily. I must have used more than a litre of the solution in total.The hundreds of exposed cups made by the chopped stems immediately drank it.
I then diluted down the remainder to my usual 1:50 and did my regular weed control in the rest of the cemetery! I could not resist a further drench of my 1:50 before I went home a couple of hours later.
You can see from the pictures that it worked very well. It was interesting to note that some stray more far spreading shoots I had left because the ‘cemetery team’ suggested they rather liked it died too. Attached to the original deep root resource it had received a lethal dose. There has been no regeneration what-so-ever since it was treated. No other adjacent plants and wild flowers were harmed. Nor was any other plant that had intermingled with Peter’s JKW.

Good news added May 2018
After two years there is no sign whatsoever of any this clump of equisetum in Bolton Percy cemetery. Quite simply zilch. Even more interesting is that a few wayward more distant shoots deliberately left since it is rather pretty, are gone too. Evidence that they were all coming from the same deep root system.

It looked completely dead one month later and now after a year has proved to be so
A few months later the silica thickened stumps were resistant to speedy decay and were disguised by a bark mulch
(sorry I have lost the picture)
I still love it at home

Although I am confident that the technique works very well on JKW and Equistum hyemale I am not sure of its general value on common mares tail where most gardeners have already chopped it. Indeed I have often recommended repeated hoeing. Control for equisetum is an either/or situation where mechanical control is not consistent with chemical control - at least at the beginning.
Nor is it easy for allotment holders when if they do manage to get rid of it, it immediately creeps back from a neighbour.
Lots of slim small detached pieces make it impossible to use the drenching technique. Nor is there contact with the deep ‘mother root’ .
If you are lucky enough(!) to start with a strong stand of unimpaired equisetum I think you will be successful. Strong luxuriant growth does have wider stem bases clustered together which in theory should take up the glyphosate very well.

In a ditch in Toulouse I think this would be luxuriant enough for cut back shoots to take up the spray
I suspect that this mares tail in a reader's garden would respond to the treatment 
Another view of equisetum
I observed on my original post how in normal undisturbed wild landscapes endemic vegetation intermingles with mares tail and they coexist together. In my post about the wildflowers of Tignes it was there up in the mountains and contributed to the wonderful ground cover carpet. It never achieved dominance amongst the grass and wild flowers. It is only when man disturbs the natural balance that it has the opportunity to build up huge reserves in its very deep root and become one of our most intractable weeds.
Even in a small corner of Bolton Percy cemetery where I failed to bother to complete its elimination a few friendly fronds have popped up over the last forty years.
In my very recent post about the very beautiful wild flowers on the cliffs at Filey it was just the same. Stunning beauty and only such as Peter and myself would ever notice the mares tail. It’s really quite pretty!

Only a botanist would notice the hugely suppressed mares tail on Filey Brig 
I feature in the following pictures Peter Williams’ own five hundred square metres of wild flower meadow. You would never know amongst the annually mown grass and long season of wild flowers that there is quite a bit of marestail. He tells me he originally tried the injection technique and as he expected it was too fiddly and gave him zero success. As mentioned above I suspect my drenching technique will only work on dense clumps.

You would never guess that amongst the long grass and the yellow rattle there was hidden mares tail
The single annual cut is now due in September. You can see how the equisetum has never stood a chance
And now in September the mares tail has been 'hammered' again. Should it gird its loins to appear (unlikely) the first frost will freeze it away
Laugh about mares tail
Readers have asked about equisetum invading their ‘clean’ garden from spores. It can spread in the wild this way but is very-very slow to establish. You would need to be grossly incompetent to allow this to happen in your garden!
The funniest thing I have ever seen was this video of equisetum spores dancing sent in by reader Sarah Stu. In case you missed it here is the link

My main post on mares tail
My main post on JKW
Read about equisetum in Tignes
Take a trip to Filey

Boundary Cottage Open Day reminder
Should any local readers come on my open day on Sunday 10 September 2017 please say hello but do not ask about my lawn (moles). NGS details are here

Brenda's cakes wait in the freezer
Beware of the conure


  1. I have my Equisetum growing in an old green washing up bowl..everyone says how beautiful it is and ask what it is . I will not be setting it free ! Very interesting post and the dancing spores YouTube video made me chuckle ! :)

    1. I imagine you remind your guests that it is a relic from the carboniferous era

  2. Very interesting - we have marestail on the allotment.
    Love the video!

    1. Probably best to keep up very frequent hoeing and collaborating with your neighbours Belinda

  3. If you only have a few horsetail to treat, there is a similar method to injection that works well. You get down to the woody base (black bit) and scrape off some of the surface. Then apply the stump killer strength glyphosate with a paint brush. It doesn’t matter if it snaps off, just take care not to lose sight of it. It’s a good method for close to ponds or precious plants, and more effective than gel. Also works a treat on brambles.

    So far this year, less than 20, so still heading in the right direction!

    1. Thanks Sarah. I think the commenting about not worrying about it snapping is a good one as long as folk realise the bit you have painted is the bottom part!
      Sarah has a long standing battle with equisetum which she has been reporting to me Congratulations on your impending victory.
      Nice that people are laughing at the link you gave me.

  4. That made me laugh, but you are right to point out that it's the root not the top that needs the treatment if it snaps. Unless horsetail is prone to placebo effect.
    Yes, nice to see the video is entertaining. Maybe someone could make one for box caterpillars?

    1. Blogger HELENE makes very fine videos like this one about wacky aphids which I love.
      Fortunately she has never had to report box caterpillar

  5. Always an informative post Roger. Wishing good weather for the opening, would love to visit, just a little to far for a day visit.

  6. One day perhaps Brian. I would love to meet you

  7. I'm afraid that Martyn and I won't be able to make your open day this year.

  8. I hav two disused allotments at the bottom of the house I purchased in August. They were riddled with Mt as were adjacent areas and also the front. Icovered with expensive roofing plastic and they seem to be black when I look underneath - are they OK to pull up or shall I deprive of light a little while longer?

    I also sprayed 350g glysophate on the 18" lush green ones today.

    Glad to have read your blog and I will get to hoeing also.

    It's my first 'big' garden as such and this seems contained at the bottom third where I hope to plant in the allotment beds (bordered with wooden sleepers) in due course.

    1. Welcome to large scale gardening anon! Read my previous posts on these two weeds very carefully.
      Frost is due to cut back mares tail anytime now so depriving them of light will make little difference until Spring -if that helps your decision
      Don't be in too much of a hurry if there is a chance of continuing to spray in early Summer. On the other hand ifyou want to revert to frequent hoeing get started as soon as they pop up'
      Keep me up to date as things unfold

    2. Thanks and will do. I see Mt on my dog walks now. Safe to say it has 'got in my mind's.

  9. Great to read this needn’t to be a massive problem in a wild flower meadow. I’m leaving our big front lawn to see what happens and have noticed a lot of mares tail (and a lot of pretty flowers) - I was worried it might drown everything else out but it doesn’t sound like it.

    1. Hopefully not - but I cannot vouch for it as I do not know the site's history. I expect you plan the occasional cut which will help


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