Thought Actaea (and Cimicifuga) germinates in a pattern of warm-cold-warm. These kind of germinators usually have an immature embryo that needs to ripen in the first warm phase. Cold period is to get rid of natural substances in the seed that inhibit germination.

Polygonatum is a species that needs a cold period for SLOW germination.

Here is a link that might be useful: Germination Database

That makes sense considering that the seeds for either would ripen in early summer. Either way -- how would you care for the containers during the summer? Keep in the shade and at least a bit moist?

Gardenprice is correct. Think about the time of year and conditions the seed would be exposed to if it ripened on the plant and fell to the ground. Sometimes just sowing and keeping the pot inside for 4 - 6 weeks, then placing outside is enough.

For seeds that lose viability if dried out long enough to store at all, I'll sow immediately, place the seed pot tucked in discreetly at the base of my pots with plants in summer/fall. I have a few permanently planted containers, larger size. When I water plants, I moisten the seed pots and they aren't forgotten as they might be if I put them under a shrub in a bed.