Thank you Tyrlych ! So upper left : Ligustrum vulgaris Upper right : Viburnum opulus But what about the two others ? They do not look like this or this
The 3rd one is really a Fallopia (syn. Polygonum) cf. japonica and I think the last one is a Picris hieracioides.
Bottom left...Fallopia japonica. https://www.google.co.uk/search?q=F...7oDYAg&ved=0CAkQ_AUoAQ&biw=1920&bih=967&dpr=1
Andre as you live in France you may still be allowed to use chemicals. Glyphosate will kill it. Apply as per instructions and be patient. It is carried down by the leaves to the roots. It does not instantly die. The plant needs to be growing strongly with a good lot of leaves. It is probably too late this year. It may need a few applications.
Many studies shows that glyphosate is not very efficient against Fallopia even with repeted applications. See this one for instance : http://el.erdc.usace.army.mil/elpubs/pdf/apccc-19.pdf
You may find this interesting. http://www.cornwall.gov.uk/PDF/JKGuidance.pdf Quote..."Stem - new plants can grow from the nodes of pieces of green stem, in soil or water. Machinery such as strimmers or flails will spread it in this way." and "Rhizome (underground stem) - pieces as small as 0.7 gramme (smaller than a one pence piece), can grow into a new plant. Breaking up the rhizome stimulates the production of small red buds which each grow into a new stem." In Britain it grows through tarmac and even concrete, covering huge areas. Destroying and native plants that used to grow in the area. Before the Olympic Games were held in London in 2012 , the whole site had to be cleared of Japanese knotweed at a cost of £70 million. Incorrect disposal of the shoots/canes can spread it even further.
Andre, is this Fallopia in your garden? If yes and you just cut it back, then next year it will be an indoor plant! For example in your bathroom... :))) http://www.botanicalgarden.ubc.ca/forums/showthread.php?t=73180&highlight=fallopia
