I grow it in 9b, and I`ve started it from seed in 9b.
I have not successfully seeded it and had it grow to maturity in 9b, unfortunately, I've only managed to do it using starts.
Nobody has given me any info on how exactly it's done here but I suspect there is some trick as to when/how you start the seeds. Right now ("deep winter," my kale and cauliflower and peas are trucking to give you an idea) I have 3 in the ground that are super happy. They require regular watering and are big prima donnas if I miss a day. They'll survive a bit into spring but then they'll mysteriously get stem rot and melt away, from one day to the next. I put them on slopy, sandy ground to try to extend it, even if it means I have to
water more.