芬兰于1976年春开始用塑料温室进行桦木人工诱导开花并获得成功,大大提前了开花年令。1976年2月4日在塑料温室播种桦木种子,播后35天进行第一次移植,60天时苗高达1米,77天时出现雄花序,92天第二次移植于塑料袋内,139天进入“秋季”,181天进入“冬季”(雄花的出现是经过人工遮黑和低温处理,使之落叶休眠, Finland started artificial blossoming and successful birch in plastic greenhouses in the spring of 1976, ahead of the flowering season. Birch seeds were sown in a plastic greenhouse on February 4, 1976 and the first transplanting was performed 35 days after sowing. The height of the inflorescence was up to 1 meter at 60 days, the male inflorescence appeared at 77 days, the second transplanted in plastic bags at 92 days and 139 days “Autumn”, 181 days into the “winter” (male flowers appear after the artificial blackout and low temperature treatment, the leaves to sleep,