Posted: 27/08/2015 at 18:10
Is it bindweed ?
That would be my guess too. If so, you'll need to let it grow so that it has plenty of leaves, spray those leaves with a systemic weedkiller such as glyphosate and then wait until it dies down, giving time for the weedkiller to travel down to the roots. It's a pernicious weed and some will still grow back which you will have to treat the same way.
Fingers crossed that it isn't bindweed as you'll have a battle on your hands if it is. If positively identified as this, avoid rotovating at all costs as every little piece will grow into a new plant.
Edit: just seen your photo after I posted. Not bindweed thankfully! Might be daylilies which can be invasive.