Those are seed pods, and seed is one way trumpet vines start. Another way (which you probably haven't discovered yet after only three years, but just wait) :) is that they sucker freely. And I do mean *freely.* You're going to have trumpet vines coming up all over the place before too much longer, so if you want to grow them from seed you certainly can (and sorry, I don't know the details of growing them from seed), but there's no need to. You'll have more than you want of them soon!

You might google "starting trumpet vines from seed" or something to find out more, if no one here chimes in.

Have fun!

Actually, I was surprised when we moved here that Chicagoans like trumpet vine so much. Where I lived south of here in Tennessee and Virginia, they are just about as common as herring. And like Kaiser Wilhelm said about herring: people would think they were a delicacy, if they weren't so plentiful!

I think trumpet vine must not be as at home here as elsewhere, or it truly would be everywhere, from what I remember. And it's really not, from what I've seen. Plus, people like it and try to grow it. My mom was always having to cut it off her trellis in Tennessee. She viewed it as a weed there.

Don't get me wrong: I love the color of the flowers and leaves and the form of it. I like that it attracts hummingbirds. I think it's a nice plant.