metaphor: the richness of the springtime when plants and crops grow big and plentiful is compared to a pregnant woman. The expression "big with rich increase" (in line 6) could refer to the fertile land where crops are grown or a pregnant woman. But the woman in this metaphor is a widow. Her husband has died and her child is both the orphan and the "unfathered fruit" (since his father has died). The birth of the child, then, is not a happy time for the widow because she will have to struggle to support her child. Similarly, the growth (or birth) of all of the fruit and other crops that the speaker sees during the summer is not a happy time for him. Just as the widow is without her husband, the speaker is without the young man.
At the end of the third quatrain, the speaker adds that the pleasures of the summer will only arrive when the young man himself appears (line 11).
As he moves into the couplet (from line 12 to 13), the speaker presents two more metaphors: the birds and the leaves. The birds are mute. They are not singing the cheerful songs that birds usually sing during the summer. Or, the speaker adds, if they do sing, it is a dull and sad song because they know that winter will be coming soon. Of course, the speaker is referring to himself. He can barely speak at all because he is so sad. And when he does speak, he does so in a sad and gloomy voice. Similarly, the speaker is like the leaves. Normally green in summer, the speaker sees the leaves as "pale." They are white, without color. The speaker also feels pale without