When my first plants started to flower and produce seed pods, I couldn't wait, wanted to see what they looked like inside, and they were still green, ok well some that I opened up all though I could see the seeds, they were still white, but others the seeds had turned brown, I planted some of those seeds, and they did sprout, and produced healthy plants. Also I noticed that with some of the ones that were still white, once the pod had been opened, often they turned brown, but I never tried planting any of those, I kind of doubt the seeds were mature enough.. However I am sure it is best to let them mature completely and the entire pod turn brown, dry out,..the seeds fall out nicely ,etc. I put them in a plastic bag too, but not air tight, actually a paper bag I think would be better, but sometimes when they dry the pods break open and spill all the seed, so some sort of container is helpful.