Sow
0.47 inches (1.2 cm) deep with a guideline distance of
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 Red Emperor about 28 days before your last frost date.
As Red Emperor is half hardy, ensure temperatures are mild enough to plant out - wait until after your last frost date to be on the safe side.