Prunus spinosa, commonly known as blackthorn or sloe, is a deciduous shrub native to Europe, Western Asia, and North Africa. It features early white spring flowers and produces dark blue astringent fruits valued for sloe gin production. Seeds exhibit complex dormancy requiring both warm and cold stratification periods, making germination moderately difficult without proper pretreatment.
Before sowing
Seeds require warm stratification at approximately 20°C for 4 weeks, followed by cold stratification at 4°C for at least 18 weeks (126 days). Some sources recommend up to 32 weeks cold stratification for maximum germination.
Sowing
What to expect
Tips
Maintain moist (not waterlogged) stratification medium throughout pretreatment. Inspect regularly and sow when approximately 10% of seeds show signs of germination (chitting). Press seeds firmly into soil without burying them deeply. Cover with 5-10mm of grit or compost. Do not expose newly sown seeds to temperatures above 25°C as this induces secondary dormancy. Some seeds may remain dormant and germinate in the second season—leave the sowing medium in place.
Sources: Forest Research UK, Tree Seed Online, Sheffield's Seed Company, USDA Forest Service, scientific studies on Prunus dormancy mechanisms
