My vegetable love should grow Vaster than empires, and more slow (lines 11-12)
This is one of the poem’s most famous passages. It’s memorable because it’s surprising, fluid, and extremely sexually suggestive. The speaker mockingly combines love and sex in the poems "If" scenario – where, ideally, love would "ripen" into sexual desire.
[…] then worms shall try That long preserved virginity (lines 27-28)
Here, the speaker, in characteristic hyperbole, seems to claim that, if the mistress doesn’t have sex with him, she will remain a virgin forever – an idea he clearly holds in contempt. Think back to his initial accusation that her "coyness" is a "crime." Here, he describes her punishment – worms! That’s not very nice – although, if you have a dark sense of humor, it can be funny, too. The lines also draw attention to themselves by rhyming "try" with "virginity," which causes us to think about what we are reading.
And into ashes all my lust (line 30)
This is interesting on several levels. It might suggest that the speaker is a virgin, too, and that he only wants to have sex with the mistress. He says that "all" his lust will turn to ashes when he dies, if she doesn’t have sex with him. If she dies a virgin, so will he. But, that’s only one possibility. The word "ashes" also suggests fire, playing on the idea of passion and lust as fire. Sounds painful.