What it is, in the photo above? It is Angelica gigas, blooming in August for weeks.
To succeed with Angelica gigas, you need to get it started in a spot that’s at least part shade, and where the soil isn’t too dry. And you need something more: You need two “generations” of genetic material, both a one-year seedling and also a batch of seed.
Since it’s biennial–meaning blooming in its second year, and simply producing foliage its first–you also need to keep a strict eye on the spot where you spread those seeds. They’ll be tiny sprouts at first, if all goes well, easy to overlook and inadvertently rake up during spring cleanup. Mark off the area where you sowed them the previous fall, and let them be.
There’s a full profile and more photos here on this oddball, chest-high wonder that always has late-summer garden visitors asking, What it is? Enjoy…or just sing along: