If you want to extend the harvest of lettuce and other leafy vegetables as far as possible in the autumn and early winter, it is important to time the sowing so that the plants are almost fully developed when the day length falls below 10 hours. After this, the growth is significantly slower due to the reduced amount of light to eventually come to a complete standstill - and the growth only really takes off again when you get out on the other side and the day length is again more than the 10 hours.
At our latitudes, the cut-off date is exactly today, where the day length is now down to 9 hours and 58 minutes. When things should be sown, so to speak, to hit the day, of course, depends on both variety and weather, but for these salads (Winter Gem and Winter Density), sowing on August 10 and planting in September has proven to fit reasonably well over the years. There are now 2 salad-filled manure benches, where the windows must now be laid over so that the leaves are not constantly wet and exposed to rot. With a little extra protection in the event of frost, the plants can hopefully last long enough for fresh lettuce to be picked almost daily for the next few months.