ORGHPS Germination Guide: Sow immediately, Either the viability of these seeds is short or the species propagates best with fresh seed. Stored seed might be coaxed into germination with temperature cycling and patience. Germination if successful only when GA3 is used. * (a) harvest capsules when they turn from green to brown and are still non-dehisced; (b) maintain seeds under non-desiccation conditions at all times; (c) treat the seed with a 24 hour aerated water soak in 1 mM GA3 before warm stratification; and (d) follow a 3 month warm stratification period with at least 7 months cold stratification. See http://hriresearch.org/docs/publications/JEH/JEH_1999/JEH_1999_17_1/JEH%2017-1-44-46.pdf

Source: Ontario Rock Garden & Hardy Plant Society