I have the blue version called False Indigo and its seeds are viable. I wintersowed some 2 years ago and they were some of the most prolific sprouters! None have bloomed yet--even the parent plant didn't last year because of our Mother's Day blizzard and the extreme cold after, but most survived and put out new growth last spring/summer. If I have blooms this year and anyone wants seeds of the blue variety I'd certainly collect and send them. I've seen quite a bit of variation in what's sold as False Indigo, I'll post pics of my blooms (hopefully!) this spring.
