Helianthus x. multiflorus? Here is a link that might be useful: Helianthus x multiflorus

Your plant does look like a Hypericum. One Hypericum (H. perforatum) is properly called St. Johnswort but most people call all Hypericums that. There are many species of Hypericum and they vary in leaf size, shape, "spottiness". The flowers vary, too; I'd say subtley but many people might think they weren't "quite right". Yours might be, but I wouldn't swear by it, Hypericum patulum. Joe

yay! It certainly looks like it. Quite a bit of power in that delicate looking plant. Now that I've seen the pictures, I've seen the ripe fruit before in many places around town.

Cosmopolitan weed, possibly a garden hybrid. Frequently asked about, appearing to be sometimes sold as O. biennis by mistake.