If you grow thunbergia in a pot, once the season is done, bring the plant inside and let it die. It will make a mess while it's dying, but you'll find the broken open seed pods and lots of seeds. Maybe some plastic under the dying plant would help to contain the mess and collect the seeds. Attached is a picture of the seed pod and a seed (small, brown, and nubby). It was my first year growing thunbergia, but now I plan to grow this in pots on either side of my front door every year!
