Ground Stuff is Yarrow, aka Milfoil, latin name Achillea millefolium.
Generally regarded as a weed (in my garden, anyway!). The common stuff
has a flat head of white flowers held on a stalk above the basal
rosette of leaves. There are selected cultivated varieties with
yellow, pink and brick red flowers that are more attractive.

See http://en.wikipedia.org/wiki/Achillea_millefolium.

Thanks Chris! I'll look that up. I have at least heard of yarrow...