“In a nursery setting, say something under five or 10 years, it's really easy,” said Bill Werner, one of the group's tree propagators.“But as they get older, material doesn't seem to respond as well.

比尔·沃纳是这个团体的树木繁殖人，他说：“在苗圃中，如果树龄小于5或10年，就非常容易，但是当更老一些的时候，各种物质就不那么灵验。

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