The catkin of the birch tree is long and slender.

桦树的柔荑花序又长又细。

The birch tree in my backyard is over 50 years old.

我后院的桦树已经有50多年了。

The growing birch tree exfoliated excess bark.

这正成长的桦树剥落了过剩的树皮.

Well, it is a birch tree. It is not as old as you think.

哎呀，这是一棵桦树。它没你想的那么老。

The second threw on his canvas a thundering waterfall, with a fragile birch tree bending over the foam;

第二位画家画了一幅轰然飞泄的大瀑布，瀑布边有一棵小灌木，细弱的枝子弯向水面上；

Significantly, this line marks the southern limit of the birch tree, a plant whose pollen is one of the causes of hay fever in northern Europe.

值得注意的是，这条线标志着桦树的南部界限，而桦树的花粉是引发北欧花粉热的一个原因。