I’ve had trouble growing shiso as well, until I learned that stratification helps. What worked for me this year was just put the seed packet in the freezer for three days before planting!

But now that this is brought up, I will save some seed and try fall sowing as well. Not sure it will survive, but maybe in a sheltered place or even a pot in a cold cellar for the winter?

I haven’t tried winter sowing, but it’s worth trying! I think this is the one that I’m growing. https://www.reneesgarden.com/products/bicolored-shiso