I saw these beautiful drifts of Wild Clary (Salvia verbenaca) on Windmill Hill in Hitchin, Hertfordshire- my home town. It's a mystery to me why I haven't noticed them before!
  Initially I thought it was Meadow Clary (Salvia pratensis) but that didn't seem to make sense. Meadow Clary is now so rare that it made national headlines about ten years ago when twelve plants were stolen from a nature reserve in Kent.
 A friend who lives in Hitchin pointed out that these are Wild Clary aka Wild Sage which is more widespread though nonetheless in decline. 

 At first I assumed it was restricted to the unmowed banks on the edge of the hill. When I looked more closely I saw the wrinkly grey-green leaves were growing in the grass everywhere. If Windmill Hill was uncut and untrodden it would be covered in the flowers of Wild Clary.
 Perhaps it has been sowed to enhance biodiversity but I assume it is a surviving colony of the species dating back to Hitchin's rural past. Certainly it is a plant of sunny, dry, calcerous grassland and Windmill Hill corresponds to its natural habitat.

 The flowers are characteristic of the Salvia family.

 Really quite stunning to see the purple haze against a froth of Cow Parsley.

 The loss of flowering grasslands has been widespread and severe so a fragment like Windmill Hill should be cherished.