I have a pretty spiderwort. I'm not sure where it came from, because it grew this year right by the steps of our porch. at first I almost pulled it up because it looked like a weed, but I left it there. I'm glad too!
I'm not sure when they die out completely but I really want to get seeds off of it. I try to find seeds every morning after the flowers have closed/died, but I can't find any. and it's been covered in bees all summer so I know it gets pollinated. Unless it doesn't have male/female parts... hm..
explain?
ive never collected spiderwort seeds, but when I want to collect seeds from an unknown plant I just make sure to check on it a few times every day. and simply observe how they go through there own process and set seed. take notice in the small changes to the flowers. specially after flowering. eventually you'll have seen the entire process with your own eyes and you will know exactly for future reference. not every flower will set and produce viable seed so keep that in mind. the best you can do is observe and learn.