Very prolific that will reseed very easily. Any seedlings that are not weeded out in their first year will be large enough to bloom in their second year. If propagation of the same color flower is wanted then growing from cutting is your alternative. Seed propagation will result in a variety of shades of blue, mauve, or even shades of lavender.1
Ensure that temperatures are mild and all chance of frost has passed before planting out, as Oiseau Bleu is a hardy plant.Blue Bird