Groundsel, Senecio vulgaris - more seed

Several of the groundsel flowers have now produced seeds and I managed to photograph this one before the they all blew away in the soft summer wind.

I still cannot work out why the groundsel and the clover grew so quickly earlier in the year when it was cold, often frosty, when the numerous seedlings that have germinated since the warmer weather started are so slow in progressing during the current 'good growing weather' - they look healthy enough, just slow.