Aim to sow
0.49 inches (1.25 cm) deep and try to ensure a gap of at least
3.12 inches (8.0 cm). Soil temperature should be kept higher than
8°C / 46°F to ensure good germination.
By our calculations, you should look at sowing Bonnie about 60 days before your last frost date.
Ensure that temperatures are mild (minimum night temperatures should be around 0°C / 32°F) and all chance of frost has passed before planting out, as Bonnie is a half hardy plant.