Sow at a depth of approx.
0.25 inches (0.64 cm) and aim for a distance of at least
11.7 inches (30.0 cm) between Common zinnia plants.
By our calculations, you should look at sowing Giant blue point about 21 days before your last frost date.
Giant blue point is tender, so ensure you wait until all danger of frost has passed in your area before considering planting outside.