I used to have a plant growing in my backyard that resembled a seeding dandelion in the fall, but 3 feet tall. It had a single, straight, woody stem that I'm pretty sure was hollow. I think the spherical head was composed of many smaller flowers, but I also doubt it was an allium.
This was in Cincinnati, Ohio, but it may not have been native to the area; my mom could have planted it. (She doesn't remember it at all, now.)
Failing that, what are some plants that resemble giant seeding dandelions?