Sow at a depth of approx.
0.47 inches (1.2 cm) and aim for a distance of at least
3.12 inches (8.0 cm) between Cabbage plants. Soil temperature should be kept higher than
4°C / 39°F to ensure good germination.
By our calculations, you should look at sowing Late Flat Dutch about 45 days before your last frost date.
As Late Flat Dutch is hardy, ensure temperatures are mild enough to plant out - wait until after your last frost date to be on the safe side.