Keep in mind when planting that White Spires 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 White Spires about 63 days before your last frost date.
Ensure that temperatures are mild and all chance of frost has passed before planting out, as White Spires is a very hardy plant.