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,即所谓进入“秋季”、“冬季”),204天回到“春季”,211天开雄花进行授粉,243天出观新的雄芯,251天即1976年10月12日收到能发芽的种子。这样一般要 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 transplant was performed 35 days after sowing. The shoots were as high as 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 artificial black and low temperature treatment, so that leaves fall dormancy, the so-called into the “autumn”, “winter”), 204 days back to “spring”, 211 days Open male flowers for pollination, 243 days appearance new male, 251 days that October 12, 1976 received germinated seeds. This is generally