Keep in mind when planting that Superbum' x 'Lady Leitrim is thought of as half hardy, so protect with a row cover whenever the temperatures drop.
Try to aim for a seed spacing of at least
11.7 inches (30.0 cm) and sow at a depth of around
0.04 inches (0.1 cm). Soil temperature should be kept higher than
18°C / 64°F to ensure good germination.
By our calculations, you should look at sowing Superbum' x 'Lady Leitrim about 56 days before your last frost date.
Ensure that temperatures are mild and all chance of frost has passed before planting out, as Superbum' x 'Lady Leitrim is a half hardy plant.