Effects of seed moisture content, stratification and sowing date on the germination of Corylus avellana seeds

For Corylus avellana, pericarp permeability, seed desiccation tolerance, and the effect of warm and cold moist stratification combinations on germination and of outdoor sowing date on dormancy breaking and seedling emergence were investigated. Seeds with (intact fruit nut) and without the pericarp were subjected to an imbibition test, and water uptake was measured. After nuts had been stored for 5 months at 3–5 °C, seeds and desiccated seeds were cold-stratified at 3–5 °C (for 0, 1, 2 or 3 months), then tested for germination. Nuts were warm-stratified at 20–25 °C (for 0, 1 or 2 months), then cold-stratified (for 0, 1, 2 or 3 months) and tested for seed germination. The nuts were sown outdoors on three dates in the same year of their collection: 15 September (immediately after collection), 2 November, and 17 December, and emerged seedlings were counted the following spring. The pericarp was not a barrier to water uptake by the seed; however, the seeds imbibed water faster and had more mass when the pericarp was removed. Seeds tolerated desiccation; germination percentage was not reduced when seed moisture content was reduced to 8.71%. Germination of seeds without the pericarp (regardless of the moisture content) was the highest when the seeds were cold-stratified for 2 months. When seeds with the pericarp were tested for germination, 2 months of warm stratification before a 2-month cold stratification maximized seed germination. For outdoor sowing of nuts, sowing date affected percentage of seedling emergence the following spring; early autumn sowing (immediately after collection) resulted in the best emergence.