Look to ensure a distance
11.7 inches (30.0 cm) between Doppelkopf seeds when sowing to make sure your seedlings have enough space.
By our calculations, you should look at sowing Doppelkopf about 42 days before your last frost date.
Ensure that temperatures are mild and all chance of frost has passed before planting out, as Doppelkopf is a hardy plant.