Others produce a cluster of flowers in an umbel at the top of the flower stem. Except for my original strain, all of mine are seed grown - from a mixed lot labeled Primula japonica . It will grow in full sun or partial shade. Most Primula are easy, warm germinators but some, including P. japonica require cold stratification. Seed does not have a long shelf life, and best results will be from fresh seed although P. japonica will give tolerable results from purchased packets.
Seed stored for more than a year is probably dead.
It's dust fine and should be surface sown since they require light for germination. Flowering begins in early May in my garden, starting with a short stalk topped by a cluster of buds, almost buried in the huge leaves. As the days pass, flowers open in a circle around the cluster of buds as the flower stalks lengthen. When one set of buds opens, another forms at the end of the flower stalk, extending the bloom period for a full month in my garden. Colors vary considerably, ranging from white through pinks, reds, yellow and orange.