[cloddopper]

Dunno DL .

 To me it's a British knot weed p[lain & simple , have a look in Google images  under the Latin name of Polygonum pensylvanicum there are some good likenesses.

[Somewhere_by_the_river]

Could you mean 'redshank' Cloddopper? Wherever there's some from of cultivation there it tends to be (though I confess to being rather partial to the garden cultivar forms of Persicaria). A google search for Persicaria maculosa will find some pics and there's a good link here: http://www.gardenorganic.org.uk/weeds/redshank

[Fleecewife]

Just noticed a plant in my garden which looks just like the pic.  I know it's not Rosebay Willowherb, but grows into something like a small, weedy version of that.  It could be called Broad-leaved Willowherb.  As I said before, you'll need to grow some on to be sure, especially with so many possibilities.

[devonlady]

Rosebay willow herb is the the big show-offy one. Common willow herb has a smaller less significant flower head.

[Penninehillbilly]

Hi WYF, our RB willow herb is growing like crazy, how about a new picture?
 
Quote - under the Latin name of Polygonum pensylvanicum
 
thats american? is it over here then? we don't have anything like that up here, just a small lower growing type. (apart from Japanese knotweed of course  )

[cloddopper]

I didn't realise the thread was still running  .  Alison has been pulling some weeds out the raised beds that mainly contain composted horse muck, coir waste and vermiculite there was plenty of knot weed .

 I could have put up some pictures of different stages of my knot weeds growth & also some of the other horse resistant weeds that have come from the same beds .