Invasives: Identification: Japanese knotweed and other invasive knotweeds

Discussion in 'Plants: Conservation' started by wcutler, Sep 18, 2010.

  1. wcutler

    wcutler Esteemed Contributor Forums Moderator VCBF Cherry Scout 10 Years

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    Judging by the company this vine with tiny white flowered inflorescences is keeping, I decided to search for invasives (as that seems to be the theme of this planter with blackberries and ivy, but maybe it's supposed to be a honeybee planting). Sure enough, I found photos of Reynoutria japonica that have the same little samaras. Is that what this is? Some of the google images filed with this name matched this exactly, but most seemed a little different from this.

    And for extra credit, are they samaras? The third photo shows what seems more like a bud arrangement, but in the last photo, they look like the seeds. I didn't realize they were different when I was looking at them. It won't be the first time I've mixed up buds and fruits.

    20100917_BurnabySt_ReynoutriaJaponica_Cutler_P1050001.jpg 20100917_BurnabySt_ReynoutriaJaponica_Cutler_P1040999.jpg 20100917_BurnabySt_ReynoutriaJaponica_Cutler_P1040987.jpg
    20100917_BurnabySt_ReynoutriaJaponica_Cutler_P1040983.jpg 20100917_BurnabySt_ReynoutriaJaponica_Cutler_P1040984.jpg 20100917_BurnabySt_ReynoutriaJaponica_Cutler_P1040989.jpg
     
    Last edited: Sep 19, 2010
  2. Silver surfer

    Silver surfer Contributor 10 Years

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    Re: Identification: Japanese knotweed

    I believe this is Fallopia dumetorum. Common name Copse bindweed.

    Your last pic shows the seeds.

    http://commons.wikimedia.org/wiki/File:Fallopia_dumetorum.jpeg

    http://en.wikipedia.org/wiki/File:Illustration_Fallopia_dumetorum0.jpg

    It is very different in its growth from Fallopia japonica. Common name Japanese knotweed.
    Maybe this excellent site will help. Japanese knotweed looks a little like Bamboo stems at the bottom. The stems are hollow. The leaves have a sort of zig-zag to them. It does not climb, but can get tall.

    http://grandpacliff.com/InvSp/JapKnot.htm
     
  3. Michael F

    Michael F Paragon of Plants Forums Moderator 10 Years

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  4. wcutler

    wcutler Esteemed Contributor Forums Moderator VCBF Cherry Scout 10 Years

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    Re: Identification: Japanese knotweed

    Thanks, Silver surfer and Michael. I guess the genus name has been changed to Fallopia? The pictures for F. baldschuanica do look a bit more like it, with the green veins in the flowers (or do the others have that?), and Wikipedia says the leaves can be oval.

    I learned (from Wikipedia of course) that the fruits are achenes, with a single seed that nearly fills the pericarp, but does not adhere to it, and a winged achene is called a samara. I guess these fruits aren't winged enough to be considered samaras.

    I thought the "Japanese knotweed" term applied more broadly. May I add the other terms to the title? In this forum, guessing the name isn't as much the point as having the ID is.
     
  5. Silver surfer

    Silver surfer Contributor 10 Years

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    Re: Identification: Japanese knotweed


    I won't object if you change it.
     
  6. Ron B

    Ron B Paragon of Plants 10 Years

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    Re: Identification: Japanese knotweed

    The common practice is to use Japanese knotweed for the one species. Sometimes it is used unwittingly for the hybrid Bohemian knotweed.
     
  7. wcutler

    wcutler Esteemed Contributor Forums Moderator VCBF Cherry Scout 10 Years

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    According to this article on Invasive Knotweeds from the Invasive Plant Council of BC,
    Bohemian knotweed (a hybrid between Japanese and giant knotweed) seems to be the dominant knotweed species in BC.

    Fallopia baldschuanica isn't listed as one of the four common ones growing in BC, according to this Key to Identification of Invasive Knotweeds of British Columbia, but maybe this planting will get it going. Just being in a planter isn't enough to keep birds and wind from distributing it, is it? I see (in this EPPO article) that it also hybridizes with Japanese knotweed.
     
  8. Michael F

    Michael F Paragon of Plants Forums Moderator 10 Years

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    From the EPPO link . . .
    Up to 15-25 m would be more accurate. One of my books reports it being able to grow 13 m in just one year.
     
  9. Ron B

    Ron B Paragon of Plants 10 Years

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    Yes, I've seen one of the climbing species quite far up trees in Seattle.
     
  10. wcutler

    wcutler Esteemed Contributor Forums Moderator VCBF Cherry Scout 10 Years

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    I was going to include another common name for it: mile-a-minute-vine.
     
  11. Ron B

    Ron B Paragon of Plants 10 Years

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    A.L. Jacobson has identified the perennial climbing one growing wild in Seattle, "where it grows to 60' into trees" as Polygonum aubertii (Fallopia a.). See Wild Plants of Greater Seattle - Second Edition (2008, Seattle).
     
  12. wcutler

    wcutler Esteemed Contributor Forums Moderator VCBF Cherry Scout 10 Years

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    Wikipedia gives that as a synonym of F. baldschuanica, so mile-a-minute-vine it is. Some other common names: Bukhara fleeceflower, Chinese fleecevine, and silver lace vine.

    I notice on a site that's selling it: "Potential pests ~ diseases: Rare". No surprise there. It's supposed to provide good cover for birds, though.
     
  13. Michael F

    Michael F Paragon of Plants Forums Moderator 10 Years

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    Same has been said in the past in Britain (e.g. W J Bean); but F. aubertii is treated as a synonym of F. baldschuanica by J P Bailey (probably the most experienced researcher in the genus) & C A Stace (Chromosome number, morphology, pairing, and DNA values of species and hybrids in the genus Fallopia (Polygoncaceae). Pl. Syst. Evol. 180: 29-52, 1992).
     
  14. wcutler

    wcutler Esteemed Contributor Forums Moderator VCBF Cherry Scout 10 Years

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    My streamkeeper friend who ID'd this as Japanese Knotweed says they've managed to defeat some of this but only by starving it over a period of several years --
    This clump near Deer Lake in Burnaby seems to have been chopped off at about 5 feet. I was told by someone else that chopping it back like this would also weaken the plant each time this is done and eventually it would die.
     

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  15. Michael F

    Michael F Paragon of Plants Forums Moderator 10 Years

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    True in theory; the problem is that in practice, once the shoots get small enough, they escape being noticed. The clearance team think they've won the battle and go away to the next task, and after a year or two, the plant is back with a vengeance.
     
  16. vitog

    vitog Rising Contributor 10 Years

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    Chopping the plants back to 5 ft won't have any impact at all. They would have to be cut back to the ground many times during the growing season to do any good.
     
  17. Lysichiton

    Lysichiton Active Member

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    It is just possible that these plants are being controlled by "cut & squirt" application of glyphosate. I don't think this is the case though, they look as if they are re-growing - what a shame.

    These invasive Fallopias have jointed canes - similar to bamboo canes. The canes are cut between two nodes & 5-10ml of neat glyphosate ("Roundup") is squirted into each one. This translocates through the plant & will give effective kill on a whole stand. The advantage is that the glyphosate is localised on the intended target & contamination by the herbicide is minimal. I do not know what the policy of Metroparks is at Burnaby lake. I know they have been wrestling with control metods for these particular nasties for several years now.

    If cut, Fallopia japonica "gets angry". The underground stem can break (fork) into not 2, not 3, but many many small stems. this makes manual control very difficult, unless the area can be mowed or grazed.

    The Fallopia (Polygonum is sometimes used as an alternate name) species have my vote for worst invasives in the Pacific Northwest (given that Himalayan Blackberries have become an accepted part of our landscape).
     

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