Keep in mind when planting that Helen Dillon is thought of as very hardy, so this plant will tend to survive through freezing conditions.
Try to ensure a gap of at least
4.68 inches (12.0 cm) when sowing to prevent overcrowding your seedlings.
By our calculations, you should look at sowing Helen Dillon about 63 days before your last frost date.
As Helen Dillon is very hardy, ensure temperatures are mild enough to plant out - wait until after your last frost date to be on the safe side.