A vase of weeds

I collected these from the road side as I was fascinated by the detail of the various stages of the flower.  I am not sure what the plant is but think it might be yarrow. The extra is a flower in the early stages of development before it unfurls to reveal the white petals.  I will be sure to dispose of these in the rubbish and not the compost in case I spread unwanted seeds through my garden.