The Echinacea flower (Echinacea purpurea), also known as the purple cone flower, native. Supposed anti-depressant. <-- I can see that, they are awful pretty to look at.
Pennsylvania Smartweed (Polygonum pensylvanicum), native. Important food for wildlife.
Purple Loosestrife (Lythrum salicaria), invasive. Derived from Europe, this pretty purple flower is choking out native plants from North American wetlands.
Thistle (Onopordum acanthium...translates to 'thorny plant that donkey eats'), super invasive noxious weed in the US.
White clover (Trifolium repens) , introduced.
Black-eyed Susan (Rudbeckia hirta), native. Same supposed uses as Echinacea.