Seed dormancy breaking under controlled conditions in ornamental Cotoneaster spp.

Seeds of numerous trees and shrubs require specific environmental conditions to initiate germination. In the genus Cotoneaster, seeds often remain dormant in the ground for 1–2 years. Therefore, knowledge of the method of breaking seed dormancy under controlled conditions is needed. Various temperatures of stratification and chemical scarification were tested in this work to break deep double seed dormancy under controlled conditions in C. divaricatus, C. horizontalis and C. hupehensis. Fruits were collected in October, when they were fully ripe. The seeds extracted from the fruits were air-dried at room temperature to a moisture content of approximately 10%. Fresh and air-dried seeds were subjected to different variants of cold stratification or warm-cold stratification with different alternating temperatures. The hard seeds of C. hupehensis were also scarified in concentrated sulfuric acid, followed by warm stratification. A seed was counted as germinated when a 1–3 mm long radicle appeared. After stratification (ca. 5% seed germination), seeds were tested for germination and emergence. The dormancy of air-dried C. divaricatus and C. horizontalis seeds was broken most effectively by stratification for 12–16 weeks at 20°/30°C (16/8 hours), followed by 15–18 weeks at 3°C. Scarification in concentrated sulfuric acid for 3 hours followed by warmcold stratification at 20°/30°C (4 weeks) and 3°C (18 weeks) resulted in the highest germination (48%) of C. hupehensis seeds at 3°/20°C (16/8 hours). In our experiment, we demonstrated that the physiological and physical dormancy of Cotoneaster species can be broken under controlled conditions with stratification or stratification combined with scarification methods.