Keep in mind when planting that Chiltern National Collection Mix 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 Chiltern National Collection Mix about 56 days before your last frost date.
As Chiltern National Collection Mix is very hardy, ensure temperatures are mild enough to plant out - wait until after your last frost date to be on the safe side.