Collect ripe plums and remove the pits
Clean all fruit flesh from the pits
Dry the pits for a few days
Crack the hard outer shell carefully to remove the seed, if desired
Place the seeds in a damp paper towel or moist peat moss
Put the seeds in a sealed plastic bag or container
Refrigerate the seeds at 35–40°F for 8–12 weeks
Check periodically to keep the medium moist, not wet
Remove seeds when roots begin to emerge
Plant each germinated seed in a pot with well-draining soil
Place the pot in a warm, bright location
Keep the soil evenly moist
Transplant seedlings outdoors after the last frost and after hardening off