Japanese Knotweed - x ways to fight

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The Japanese Knotweed is No. 37 on the world's list of invasive neobiots, even in your garden, he will start from takeover attempts from favorable locations. Exterminating through control becomes difficult, but pushing it back can be quite successful, through various measures and with some patience:
Classification, appearance and confusion
The Japanese Knotweed belongs to the family Knotweed and the genus of wingknot oak (Fallopia), its scientific name is Fallopia japonica.
Japanese Knotweed recognize:

  • The Fallopia japonica is recognizable by its special feature: the stem grows in a zigzag, every few centimeters a more or less distinct crease
  • At the kinking sites, the leaves begin to have the shape of a linden leaf, but can grow up to 18 cm long
  • These leaves are not oblong and slightly wavy as in other knotweeds, but shorter and terminate in a straight line, approximately perpendicular to the petiole
  • On the outside (close to light), elongated inflorescences appear in the leaf axils in August, with many small, creamy white flowers
  • They lay down the stems or stand vertically at the stem
  • The deciduous, perennial herbaceous plant grows very fast
  • A larger Japanese Knotweed makes up a single sprawling green leaf mass
  • In late autumn, the plant moves in, the leaves turn yellow
  • Then the leaves fall, leaving behind a forest of upright shoots and dry leaves on the ground: gigl.org.uk/GiGLer/wp-content/uploads/2013/12/Knotweed_growth.jpg
  • The above-ground parts die off during the first frost
  • In spring, new stems appear from the rhizomes, initially growing up: thegardenat485elm.org/wp-content/uploads/2015/05/SXC-800px-Fallopia_japonica_-_Japanese_knotweed_Japanintatar_Parkslide_C_IMG_6997.jpg
  • The picture shows very well that the zigzag is not always pronounced
  • The thick hollow stems ("Rameten") are often formed nestsweise: upload.wikimedia.org/wikipedia/commons/0/0c/Fallopia-japonica%28Staude%29.jpg
  • The upright growth will soon hang over: newfs.s3.amazonaws.com/taxon-images-1000s1000/Polygonaceae/fallopia-japonica-ha-ahaines-e.jpg
  • Under favorable conditions, the Knotweed grows in a few weeks to heights of 3 to 4 meters
  • This corresponds to an increase of 10 to 30 cm per day...
  • Japanese knotweed likes to grow on banks of flowing waters (rivers, lakes with inflow and outflow)
  • In addition, it is found on industrial wasteland, on the roadside, on slopes, on irregularly mowed grassland and in the forest (less vigorous)
Possible confusion:
  • The Sakhalin Knotweed Fallopia sachalinensis has straight stems and usually much larger leaves with heart-shaped leaves
  • Fallopia x bohemica: natural hybrid of Fallopia japonica and Fallopia sachalinensis, also looks like a mixture of both
  • Rarely does one see the small-sized variant of the Japanese knotweed, Fallopia japonica var. Compacta, it has roundish leaves with a diameter of approx. 10 cm
Proper description must be made, but in combat you may not care much about which knotweed it is - all of these species are classified as invasive neophytes. Even if you were to fall by the wayside and tackle Fallopia (Polygonum) aubertii, the architect-gratered urchin Fallopia (Polygonum), that would not be a drama for a long time: Just plant it again and climb another few meters in the next season,
So the Japanese Knotweed came to us
The Japanese Knotweed comes from Asia and was introduced to Europe in 1825 by Philipp Franz von Siebold. He was to make a career as an ornamental plant and livestock feed plant and in the forestry industry as a substitute for deer and covering plant for pheasants. The career as a useful plant was not so good: As a cover for pheasants, he is good, because he loses his leaves in winter, deer does not eat it and probably not our grazing cattle - nowadays you try occasionally sprawling Japanese knotweed by grazing To bring control, Heidschnucken do not like him already, just in normal Carinthia sheep and goats can try on him. For this, the beekeepers have discovered the Japanese Knotweed for themselves, it is an excellent bee pasture in early autumn. Although the Federal Nature Conservation Act prohibits the planting of alien plants into the wild, beekeepers have generously distributed the Japanese knotweed in the area - a first step on the road to expansion, currently ranked No. 37 in the Global Invasive Contributing to the Species Database (World Database of Invasive Species).
Propagation strategy and its effects
But there were even more people involved, which lacked sufficient vision, the ornamental careers career of the Japanese Staudenknöterichs ran pretty well from the start: From 1849 he was marketed by the nursery of Siebold in Leiden, the Netherlands, really nice and expensive, he quickly became a trendy plant For the then emerging garden style "Wild Gardens", prominent garden architects recommended his planting. In 1872, the first release was taken, from the grounds of a derelict nursery near Zwickau, numerous spurned cover and cattle and knotweeds spread through their rhizomes, illegal disposal of garden waste into the nature contributed their part - today Fallopia japonica is everywhere wild and sprawling in Central and Western Europe in the wild, frequent and widespread. Originally mainly riverside were settled, today it also appears at remote locations, with further spread is expected.
The Japanese knotweed rhizome makes dense and extensive populations, the more woody rhizomes from year to year survive the winter with us without problems and reach up to 2 m deep into the ground, where they spread horizontally creeping. Japanese knotweed is hardly overgrown by other herbaceous plants, after injury of the rhizome a small plant grows from each small fragment, also from parts of the stem. Aussamen happens to us hardly, but is theoretically possible. By flowing water or earth transport in the course of construction, the Japanese Knöterich is distributed more and more until all of Germany is a green Knöterich hell... So far we should not let it come, the Japanese Knotweed makes with its exceptional vigor and robustness our native flora flat, even in nature reserves. Its dense populations allow hardly any growth of other plants, as it is visited by only a few insects, it harms by displacing native food plants our insect world, on streams it slows the outflow of flood, on strongly built river sections, he can increase the risk of erosion.
Preventive measures
Japanese Knotweed should still be found occasionally in the trade, but the Central Association of Horticulture recommends the traders to renounce trading in Fallopia japonica. In Switzerland and England the sale, propagation and planting of Fallopia japonica are prohibited, F. sachalinensis and F. x bohemica are not much better. Even hobby gardeners can only be advised not to let any of these three Fallopia species come near your garden. Also not with rhizome barrier, which is the Japanese knotweed usually no halt. Even for tubs, you should plant a maximum of one fallopia aubertii or tamer eggs. Because it is simply no fun to constantly have to pay attention to the fact that no plant part "grows out" in a container plant to greet you at some point on several square meters at the end of the street. The cultivated variety Fallopia sachalinensis "Igniscum", which has just been tested as an energy plant, is sometimes recommended as harmless to gardens. But also stands as a possible invasive neophyte on the "warning list" to the blacklist of invasive species (Federal Agency for Nature Conservation).
If a Fallopia japonica, Fallopia sachalinensis or Fallopia x bohemica are already on their property and are preparing to take over, it will be difficult. An overview of the considerations to be made and the possible measures, including the reported prospects of success:
  • 1. Finally you could destroy a Japanese potato possibly by excavating all rhizomes. However, you would have to dig out your garden, as the rhizomes reach a depth of up to 2 meters. When disposing of the soil material you would need to make sure that the fallopia rhizomes do not drive out somewhere, they could be held liable. By composting with continuous addition of fresh compost this should be prevented. The dredged area must be covered well above 2 mm thick with new soil so that ev. Remaining rhizomes do not expel.
  • 2. By destroying aboveground plant parts, Japanese potato can be pushed back a bit in the long term. For this purpose, every emerging shoot is cut back directly from the beginning of the shoot in spring. At least once a month, until dying in autumn. The plant parts are destroyed to the smallest part, best burned, in no case on the garden compost.
  • 3. On suitable areas, the Japanese knotweed can be pushed back by mowing. For this he should be mowed in the first years at least eight times in the season.
  • 4. Similarly, grazing with sheep may work.
  • 5. When pushing back, you have to expect a few years of work in all methods. If you stay consistent and proceed with care, the plants could be exhausted after 5 to 6 years and die.
  • 6thWith all these measures, you must ensure that rhizomes or plant parts are not spread over equipment, transport vessels or excavated earth.
  • 7. On suitable areas (embankments, banks) pastures can be set (see ufersicherung.baw.de/pdfs/fuer_die_praxis/20140724_Kennblatt_Weidenspreitlagen.pdf), the pastures are to hinder the regrowth of the knotweed.
  • 8. Control with broad spectrum herbicides (total herbicides such as glyphosate) is possible, but only control, and the use of glyphosate may be under the impact of the current dispute over this remedy (see: tagesschau.de/inland/glyphosat-111.html) not recommended. The broadband herbicide would need to be selectively injected into the lower segments of the plant at intervals of 4 to 6 weeks in the middle of the year. Monitoring and control in the next two years should be imperative for lasting success. However, total herbicides are also detrimental to other plants / the garden soil, because of their effect on non-target organisms in the area of ​​waters not approved and generally use with the utmost caution.
  • 9. Some other methods have been tested with moderate success: Hot steaming, kills subterranean Knöterichteile, but also all soil organisms and costs a lot of energy; Covering with black plastic sheeting is now since March 2013, in the attempt you could still get in, in case you can endure a black plastic garden; In April 2010, a British research institute began suspending Japanese leaf fleas that eat only Fallopia japonica, but reports of its successes are pending
Do not fret, but use
If controlling the Japanese Knotweed in your garden requires constant cutting of young shoots, the anger can become a joy. Any plant can do anything, and the Japanese Knotweed can do a lot:
  • His young sprouts are edible and should taste good
  • When they are very young, they should be prepared as asparagus
  • Otherwise, process like vegetables, first fry and then roast, or like rhubarb, in crumble, cake, compote, chutney, relish
  • It contains phytoestrogens that are considered to be healthy in their natural form and ingested with normal food
  • And Resveratrol, the red wine known plant compound with antioxidant properties
  • However, also oxalic acid, the consumption of large quantities v. a. is harmful to kidney patients
  • However, it is dissolved during cooking, purging the cooking water reduces the content considerably
  • Therefore, young rods, up to 40 cm, with further growth, the oxalic acid content increases more and more
In 1991, a Fallopia japonica extract under the name Milsana® was launched as a plant protection product, the use of which is still partially recommended today. Milsana is not approved as a pesticide and probably no longer on the market, whether self-made Fallopia japonica extracts (Jauchen or cold approaches) any benefit, is open.
Planting should not even be done in the tub, destroying the Japanese Knotweed is practically impossible, but it is possible to reduce the Japanese Knotweed, possibly until its death. Until then you can harvest a lot of young sprouts and eat them with pleasure...

Video Board: Natural control of Japanese knotweed: BBC Radio 4 Today programme interview.

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