Improving seed germination and seedling emergence in the Juniperus communis

The observed juniper decline, lack of natural regeneration, and disappearance of numerous populations of the common juniper in Poland, were the major reasons for initiation of research on its sexual propagation and seedling production. This study shows that seed dormancy in this species is broken by warm-cold stratification at 15°C/3°C, for 14+12 weeks, respectively. Seed drying for 72 h at room temperature in the middle of the warm phase (i.e. after 4–8 weeks of stratification at 15°C) and the following cold stratification at 3°C, cause a significant increase in seed germination capacity at cyclically alternating temperatures of 3~15°C, and in seedling emergence in growing trays (67 cells each) in a greenhouse. However, seedling emergence was over 2-fold to 4-fold lower in an open nursery than in the greenhouse. After sowing in the nursery, secondary dormancy was probably induced, because some seeds germinated in the following year. Some very young, 2-year-old seedlings started to produce male or rarely female cones. This study also showed that soil conditions of mother plants can influence the pattern of seed germination and seed ling emergence.