杨树和榆树是我区造林的主要树种,种源比较丰富。每年的五月下旬至六月上旬,正是杨榆树的成熟期,要抓住时机采集杨、榆树种子,既加快绿化步伐做出贡献,又能增加经济收入。杨树雌雄异株。母树的果实为穗状蒴果,种子细小,藏于蒴果内的绒絮之间。蒴果成熟后容易自行 Poplar and elm tree is the main afforestation area species, provenance is rich. From late May to early June of each year, it is the maturity period of Yang Yushu. It is necessary to seize the opportunity to collect the seeds of Yang and Ulmus so as to contribute both to accelerating greening and to increasing economic income. Poplar dioecious. The fruit of the mother tree is a spike capsule, the seed is small, hidden in the velvet between the capsule. Capsule easy to self-maturity