Try to aim for a seed spacing of at least
1.95 inches (5.0 cm) and sow at a depth of around
0.98 inches (2.5 cm). Soil temperature should be kept higher than
13°C / 55°F to ensure good germination.
By our calculations, you should look at sowing Unifolium about 28 days before your last frost date.
As Unifolium is very hardy, ensure temperatures are mild enough to plant out - wait until after your last frost date to be on the safe side.