Keep in mind when planting that Leuchtkäfer is thought of as very hardy, so this plant will tend to go dormant over the long winter months.
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 Leuchtkäfer about 63 days before your last frost date.
As Leuchtkäfer is very hardy, ensure temperatures are mild enough to plant out - wait until after your last frost date to be on the safe side.