Stanza 3 Summary

Get out the microscope, because we’re going through this poem line-by-line.

…Then when I was sixteen, you left on a long journey
Through the Gorges of Ch'u-t'ang, of rock and whirling water.

Two years after she's married, the speaker's hubby goes off on a "long" journey. Oh man—and this happens just as this shy girl was beginning to enjoy her marriage.
The speaker's description of her husband's journey gives us a sense of how dangerous it is. He's going to be making his way through gorges "of rock and whirling water." The gorges of "Ch'u-t'ang" are near the Yangtze river in China.
It sure sounds like a hazardous journey. Come back safe, hubby!
The speaker continues to address her hubby directly in these lines, as "you." So the poem kind of feels like a letter.
The speaker's hubby isn't there, but the speaker speaks to him as though he is right there.

And then came the Fifth-month, more than I could bear,
And I tried to hear the monkeys in your lofty far-off sky.

All those months are whizzing by (five, to be precise) and the speaker's hubby is still away. She's really missing him now.
What does the speaker mean when she says that she "tried to hear the monkeys" in his "lofty far-off sky"? Well, she's trying to connect with her husband, despite the long-distance, by imagining the landscape that he's moving through.
Maybe wherever he is there are monkeys, and he can hear them, and so she tries to hear them, too.
Seriously, long-distance relationships were really hard back in the day. In the absence of Skype, all the speaker can do is try to listen to the imagined monkeys that are hanging out somewhere near where she guesses her husband is now.

Your footprints by our door, where I had watched you go,
Were hidden, every one of them, under green moss,
Hidden under moss too deep to sweep away.

The image of the footprints hidden under moss gives us a sense of how much time has passed. The moss is "too deep to sweep away." It's been so long since the husband's departure, that that moss has covered the hubby's footsteps.
These lines also give us a sense of how closely the speaker watches time pass. She's going out there checking for her husband's footsteps, and seeing whether they're still there. She's kind of obsessed, in other words. Time is passing and she's waiting, and her hubby's still not back.
Now that we've gone through a lot of the poem, notice that the language is very simple and straightforward. It sounds more like prose than poetry. There are no rhymes, and the lines are of varying lengths. This gives the poem a very conversational tone, as if the speaker is just speaking her thoughts. (For more on this, hit up "Form and Meter.")

And the first autumn wind added fallen leaves.
And now, in the Eighth-month, yellowing butterflies
Hover, two by two, in our west-garden grasses.

These lines also emphasize the sense of time passing. The seasons are passing. The autumn's come, and the leaves are falling off the trees. The months are rollin' on by. Now "the Eighth-month" has arrived. By giving us a sense of the changes taking place in nature, the speaker gets us to understand how much time has passed.
The image of the butterflies hovering "two by two" also evoke the speaker's isolation. The butterflies all have hubbies, but the speaker doesn't. Unlike the butterflies, she's alone—bummer.

And, because of all this, my heart is breaking
And I fear for my bright cheeks, lest they fade.

This is the first time that the speaker tells us explicitly how her sweetheart's absence is affecting her. Her "heart is breaking." This is some serious sadness. This girl's not very good at dealing with long-distance relationships, is she?
When the speaker tells us that she fears that her "bright cheeks" may "fade," she's telling us two things. First, she's telling us that she's so miserable that she's afraid that she's going to lose her good looks worrying over her hubby.
When we're unhappy, we don't look very good—our cheeks get pale, we look tired. This is what the speaker fears.
Second, by talking about her bright cheeks fading, the speaker also evokes the passage of time. She's afraid that her husband will be gone for so long that she's going to lose her youth waiting for him.
In both cases, her cheeks represent the health of her whole person—body and mind. In the poetry biz, we call that technique synecdoche.