Is stratification necessary for aquilegia seeds?

Question

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.

Answer 1

Assuming the Aquilegia seed you bought was for the May flowering types, the one thing to know about seed from these is they should be sowed relatively fresh, then exposed to cold. Where you live, planting them in mid to late summer is ideal, (in other words, when they would naturally fall from an Aquilegia plant already growing) with a cold spell of winter to follow, and they should germinate the following spring. However, with commercially produced seed, the viability may well be poor, depending on how long they've been kept, either by yourselves or by the supplier, because the 'viability window' of these seeds is short.

Answer 2

The seeds would require stratification, but assuming you got them from a store the supplier almost definitely would take care of that themselves.

When did you sow your seed? Spring or early summer is ideal. Did you keep them watered well? How deep did you plant them?