Nipplewort

Nipplewort, Lapsana communis.  Lullingstone Country Park, 14 October 2011.

One of the many plants with yellow composite flowers. But this plant has a simple distinguishing feature. It is the only yellow composite whose seeds do not have a hairy pappus, the organ that makes up the parachute of dandelion seeds and other similar wind-borne seeds.

You can see the maturing seeds to the left of the open flower. They seem to spread effectively, even though they can't be distributed by the wind.