We had bought a variety of aquilegia seeds. Of more than 100 seeds only one developed into a plant flowering in the second year. They weren't all sown on the same soil, so it is not very likely that the selection of the soil was wrong.
We think this is a very bad yield. We did not stratify them, because the instructions of the seller didn't tell us so.
But there must be something which can be optimised. Could stratification or late sowing be necessary?
Update according to questions
The seeds were sown into trays for our balcony railing. They were sown in spring (Apr) and very shallow to let some light onto them. Besides two seeds none of them had germinated until fall. We had 6 or more sorts (e.g. Aquilegia caeruela, A. glandulosa, A. flabellata...)
They were sown 5mm deep. Soil was rather moist.