I really, really hope I'm wrong, but this looks suspiciously like newly emerging growth of Japanese knotweed, though I can't tell for sure until its got bigger. If it is, nothing will get rid of it, though there are specialist companies that will deal with it. Note that you must not dispose of this in your garden rubbish, in your household rubbish or at the council dump without telling them what it is - it's classed as an environmental hazard, though not poisonous in any way, but because any tiny piece of it roots and is impossible to eradicate. With any luck, I'm wrong, and someone else will recognise it as something less devastating.

Thanks for your answer - not what i wanted to hear but its somewhere to start.

Well I think it might be Mares Tail.

Well Docbob's pretty good at this.

I've just googled Japanese knotweed and its not that - it only grows to about 30 cm high and is spikey looking in a spiral way (if that makes any sense?) we had it last year and thought we'd dug it all up!?

Just been reading about Mares Tail and control - there's a product called Kibosh that works, but looks like it might only be available to professionals, not the public, not sure. Otherwise, it seems to be a job for repeated applications of glyphosate - roundup or similar, with the suggestion that you bruise or slightly crush to stems before applying it to aid penetration.

I've just googled Mares tail - its a match, thank you very much Doctorbob.

we've got loads of it in my area, never seen it before (or remember doing). Thanks, was wondering what it was.

I'm very glad! Funnily enough, it's not a weed I've ever come across in my part of London.

I've just been reading about it and how it like poor soil - it makes perfect sense - that side of the garden is a real problem, we had to have a old cherry tree taken down because it was diseased and an acer tree thats on that side that's going the same way!?

Try SBK, painted on neat with a small brush, It's roots can go down as much as 4 feet, I keep digging it up and laying it out to dry.

thanks again Doctorbob.

I have spent a couple of hours today pulling up Mares Tail - it loves my rockery. Every year it comes up but the more you pull it up the less you get - till next year!

I got rid of it - eventually - with Roundup. Again. And again. And again. Etc.....

Yes thats it exactly Beattie

Yes it is definately Marestail. I have used Kibosh (now called Kurtail) on this weed with great success. Roundup and SBK are very limited in comparison.
Kurtail is a professional use herbicide, however, "Grand Father Rights" still apply if you are born before December 1964,and using the product on your own land (not a contract service). This may mean you can use this product without a certificate of competence. In my experience, its the only answer. Product link below:

http://www.progreen.co.uk/Weed-Killers/Total-Weed-Killers/Kurtail-0-5LTS/prod_2.html

I hope it is Marestail because if Bamboo is right that's a hole new night 'Mare'!!!