Typically, it is recommended to sow kale seeds in late summer for a fall and winter harvest....at least that is the practice here in the US in milder climate zones (7 and up). 6-8 weeks before the predicted last frost date but early enough for the plants to develop some maturity before the days become too short.

6-8 weeks before the predicted last frost date

What exactly does that mean? Do you mean the first frost date? Or the last frost date of the calendar year?

Oooh!! Sorry....that makes no sense!! Yes, the first frost date of the calendar year. In my location, that would be approx. 11/10, so I could sow seeds up to approx. 9/10. I'd go earlier as the days tend to be quite short at that time of year in my very northerly location. But I trust you get the idea.

That is interesting and very different from practice here. If I sowed kale seed so late in the year the plants would not achieve any size by the onset of winter which is when I'd want to start harvesting. They must grow very fast over there to provide a fall and winter harvest in 2 months.

I am in similar zone and kale survives many winters including light snow, and may still be growing in spring. It got totaled last year though due to the severe freeze.

The main thing for me is getting enough sunlight for seedlings to be sturdy before the fall light changes- the more established kale does fine with less than full sun, similar to many types of greens which can be grown in the less sunny spots & save sunny for those that really need it. So August is a good time, but another problem is that’s also drought season here, so have to really water or pouf, seedlings die.

So, I often start kale seeds in medium pots that I can put in full sun, sometimes tucked near the tomatoes or peppers or in front yard, and I have had good luck pricking out seedlings & transplanting. Growing a real “ plug” is better for transplanting but the plugs dry out so fast if I turn my back.

Sometimes I will break down and buy transplants from a nursery if I didn’t start seeds in time. Nurseries here don’t get fall veggies until later— sometimes too late if transplanting to less sunny area, as light patterns are already changing.

Also 50 kale plants is a LOT of kale at maturity , though not so much if you harvest baby leaves.