Sow at a depth of approx. 0.2 inches
(0.5 cm) and aim for a distance of at least 7.8 inches
(20.0 cm) between Calendula plants. Soil temperature should be kept higher than 10°C / 50°F
to ensure good germination.
By our calculations, you should look at sowing Flashback about 35 days before your last frost date.
As Flashback is half hardy, ensure temperatures are mild enough to plant out - wait until after your last frost date to be on the safe side.