Try to aim for a seed spacing of at least
3.9 inches (10.0 cm) and sow at a depth of around
0.23 inches (0.6 cm). Soil temperature should be kept higher than
13°C / 55°F to ensure good germination.
By our calculations, you should look at sowing Green feast & red robin f-1 about 28 days before your last frost date.
As Green feast & red robin f-1 is very hardy, ensure temperatures are mild enough to plant out - wait until after your last frost date to be on the safe side.