Try to aim for a seed spacing of at least
11.7 inches (30.0 cm) and sow at a depth of around
0.23 inches (0.6 cm). Soil temperature should be kept higher than
5°C / 41°F to ensure good germination.
By our calculations, you should look at sowing Bath Cos about 60 days before your last frost date.
Ensure that temperatures are mild and all chance of frost has passed before planting out, as Bath Cos is a tender plant.