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. Sow @ 4°C for 3 weeks, then place at 20°C. Requires soaking. Place in warm water until seeds swell, usually 24-48 hours. Discard water and any seeds that remain floating. * sow fresh or soak old seed; prechill 4 weeks or place outdoors over winter and bring indoors once germinated to avoid temperature shock; transplant at 4 leaves

Source: Ontario Rock Garden & Hardy Plant Society