Doves panic is over reaction
it is not japanese knotweed, now that is HELP!!!!
The seedlings are easily recognised and can be pulled up' just leaving a few to flower, i love them. let the bees enjoy them then compost . as u said roots are so small its easy to pull up.
As I said, I lived next door to an idiot who tried to recreate his hippy youth and planted these things in an inner city back garden and let them grow totally uncontrolled - we moved out some 5 years afterwards and were still pulling the blessed things up every few days throughout the spring and summer - when we visit former neighbours they are still complaining about it. They catapult their seeds over 6 ft high fences and have spread along the gardens of the whole street - they are a total pain - and anyway, I didn't say 'Help!' I said Aaargh! and I meant it.