Tansy...

...aka Bitter Buttons, Golden Buttons or Cow Bitter, with a really tiny hoverfly which was very hard to focus on. I hadn't realised how many uses there are for Tansy until I checked on wiki. It's has culinary, medicinal, and floral uses as well as being used as a dye, ant repellent and as a smoker for bee keepers. Who'd have thought it?