I'm in a colder zone, so maybe my comments shouldn't count. But early on in my hybridizing I experimented with this. I sowed a row of seeds in the late, late fall, like way too close to when the grounds starts to freeze. And then the next spring, I planted a row right next to using the same seeds.
I gained plants from both sets of directly sown seeds. More Spring seeds germinated than fall seeds. The Spring seedlings grew to maturity (started blooming) sooner than the fall grown seeds, for the most part. But there were plenty of successful plants from fall-sown seeds. Finally, none of the directly sown seeds germinated at the high rates I get with seeds I start indoors in February and plant outside around Mother's Day.
Also, our ground freezes hard and many inches deep. That may be why more spring-sown seeds germinated than fall-sown seeds. But it didn't seem to make that much difference.
I've been thinking about this a lot this year. I'm not getting any younger, and it's a ton of extra effort and resources to plant seeds indoors over winter, water them, feed them, and then go out and plant them when it's warm enough in the spring. So even if my germination percentage isn't nearly as good as seeds started indoors overwinter, I can just plant more seeds directly outside and all it will cost me is maybe an extra year of development before I can truly evaluate them.
