Keep in mind when planting that Ton de Waard is thought of as very hardy, so this plant will tend to survive through freezing conditions.
Try to ensure a gap of at least
11.89 inches (30.48 cm) when sowing to prevent overcrowding your seedlings.
By our calculations, you should look at sowing Ton de Waard about 56 days before your last frost date.
Ensure that temperatures are mild and all chance of frost has passed before planting out, as Ton de Waard is a very hardy plant.