Look to ensure a distance
1.62 feet (50.0 cm) between seeds when sowing - bury at a depth of at least
1.95 inches (5.0 cm) deep. Soil temperature should be kept higher than
5°C / 41°F to ensure good germination.
By our calculations, you should look at sowing White about 14 days after your last frost date.
Ensure that temperatures are mild and all chance of frost has passed before planting out, as White is a tender plant.