The hill above Penclawdd is currently the only known location in Glamorgan for the rather unobtrusive Annual Knawel (Scleranthus annua) which has not been seen since Quentin Kay reported it as abundant here in 1992. I visited the site last year and failed to find it, which was hardly surprising as it was pretty much ungrazed wall-to-wall Hedge-mustard (Sisymbrium officinale) as shown below. However this year the condition of the field was much more suitable, having been disturbed and grazed and in a 15 minute lunchtime search I managed to locate about 20 plants.
Left, field in 2010 and right, the same field in 2011
Also lots of Knotted Clover (Trifolium striatum) in the field.