Excuse me where is the yarrow? The photo below is yarrow, it is a herb, here the wild version comes in white and pink, domestic ones also come in red and yellow. It has a whirl of flowers and leaves like fine feathers it also has a distinctive odour to the leaves and stems, whereas the flowers are almost odourless.
Courtesy of "Traditional and Folkmusic" Dick Gaughan singing the "Dowie Dens of Yarrow" a traditional Scottish song.
What did you do to make it happen?
Removed the schrub canopy that was shading it