[lordthanatos]

hiya got this popping up all in one area so wondering if its something from a previous owner?

[savbo]

looks quite like celery but as there are some poisonous weeds in the same family I'd proceed with caution...

[Yorkie]

Unless it's an unusual variety I think the leaves are wrong for celery
http://www.rhs.org.uk/Gardening/Grow-Your-Own/Veg-A-to-Z/Celery

But I don't know what else it might be 

[RichardA]

guessing == horseradish or the weed we call cow parsley around here

[mumofstig]

lovage?

pic here

[Yorkie]

The leaves aren't right for cow parsley or horseradish either.

Think you might be closest / right, Mum 

[Marston]

Looks very much like lovage.I have just taken a root from a neighbour and after seeing the size of his plant I have put it in a pot.It is growing very quickly so I would advise some control over yours.

[lordthanatos]

defo lovage as the leafs are lined with red tinge which is same as the sample pics

many thanks guys

[lancashiregardeninggal]

I thought it looked like a parsnip and they do seem to be growing in a row - I have a couple still in I forgot to pull out and they are tinged with red at the bottom of the leaf stalk - apologies though if I am wrong

[Aidy]

Looks like lovage, break a leaf and see it smells of celery, or am I thinking of something 

[arugula]

Lovage - definitely! I planted some last year, decided I didn't like it and pulled it out..... or so I thought..... And you thought horseradish was invasive, its coming back up again with a vengence.