Aim to sow
1.95 inches (5.0 cm) deep and try to ensure a gap of at least
11.7 inches (30.0 cm). Soil temperature should be kept higher than
18°C / 64°F to ensure good germination.
By our calculations, you should look at sowing quadricolour about 10 days after your last frost date.
Ensure that temperatures are mild and all chance of frost has passed before planting out, as quadricolour is a tender plant.