I have no idea where you are on the planet, Stringy, but some of the leaves look rather like Hellebor. I would think that they could readily be controlled by simply mowing the lawn.

I'm in UK and that's what I thought it looked like too. Was thinking maybe a selective spray as a longer term solution. Thank you for your comment, much appreciated

If you keep mowing its unlikely you'll need a spray. They will die off it they can't photosynthesise.

Aren't they Hellebor? Self-seeded maybe?

Interesting that they are growing in a straight line.