Stratify seeds

Stratify seeds: In horticulture, stratification is the process of pretreating seeds to simulate natural winter conditions that a seed must endure before germination. Many seed species undergo an embryonic dormancy phase, and generally will not sprout until this dormancy is broken. The time taken to stratify seeds depends on species and conditions; though in many cases two months is sufficient. --Wikipedia http://en.wikipedia.org/wiki/Stratification_(botany)