Sow at a depth of approx.
0.47 inches (1.2 cm) and aim for a distance of at least
8.97 inches (23.0 cm) between Brussels sprout plants.
By our calculations, you should look at sowing Bedford - Winter Harvest about 21 days before your last frost date.
As Bedford - Winter Harvest is hardy, ensure temperatures are mild enough to plant out - wait until after your last frost date to be on the safe side.