Yesterday I was botanising in Ditchingham along the edge of field of barley stubble and found my first bristle-grass of the season. Rather suprisingly it was what I think of as an uncommon species: Rough Bristle-grass Setaria verticillata. The one I find most often hereabouts is Yellow Bristle-grass Setaria pumila, followed not very closely by Green Bristle-grass Setaria viridis.

Rough Bristle-grass was growing almost all the way along the margins beside the footpath. The characteristic backward-pointing (i.e. away from the tip) barbs on the often carmine-tinged bristles made the heads very burr-like and removing thistledown from them was impossible. This must be an effective dispersal mechanism and you'd have thought this species might therefore be found more frequently than the others.
At one end of the field the presence of the bristle-grass overlapped with that of Common Amaranth Amaranthus retroflexus. I used to associate bristle-grasses and amaranths with the plant-hunting season coming to close but now they just seem to herald the start of another interesting phase.