These plants are beautiful all year; the early golden flowers give way to attractive starburst fruiting structures, and in the fall the leaves turn a lovely bronzy color. 

Golden alexander leaves feed larvae of swallowtail butterflies, and the flowers are an important early source of nectar and pollen for small bees. 

If you want this in your garden, you will probably need to get a plant or start some seeds. Once you have it, you can watch for seedlings to come up; the leaves are pretty distinctive. Just be careful not to weed it out or suffocate it with mulch. It's easy to transplant if it comes up in a place where you don't want it. While it does spread by seed, it really isn't considered weedy like fleabane or spiderwort might be. Golden alexanders often bloom at the same time as Amsonia hubrictii (bluestar) and they look great planted together. 

Zizia aurea is the species we have on the trail; it likes plenty of moisture and sun but seems pretty adaptable to partial shade. A related species, Zizia aptera, is also available. It seems to be less common and more suited to dryer areas.