In the poem "Love Song for Lucinda" what is the rhetorical situation?

Rhetoric is the art of persuasion. To understand the rhetorical situation of "Love Song for Lucinda" we need to understand what the speaker of the poem is trying to persuade Lucinda to do, or to understand.
The speaker is trying to persuade Lucinda that love is enchanting, dangerous, and breathtaking, but worth the risk. We can assume that he is in love with her, but she is holding back.
In the first stanza, the speaker likens love to a ripe plum growing on a tree. He says that if Lucinda's tastes love once, she will be enchanted by it forever. He writes:

Taste it onceAnd the spell of its enchantmentWill never let you be.

However, that is not the end of the story. In the second stanza, the speaker warns Lucinda that love is a flame that will burn her eyes if she looks too hard. He tells Lucinda not to overthink love, and not to examine it too hard, implying she should just jump into it:

LoveIs a bright starGlowing in far Southern skies.Look too hardAnd its burning flameWill always hurt your eyes.

In the final stanza, the speaker compares love to the top of a mountain. He warns her not to end up too deeply in love, not "to climb too high," if she wants to keep her breath. However, he also implies that it is good to be breathless.
In holding out love as an enchanting, bright, dangerous, and breathtaking experience, the speaker is attempting to persuade Lucinda to take a risk. We can assume from this that Lucinda is a person attracted to beauty, danger, and adventure. The speaker is saying that love, while dangerous, is exciting.
The speaker uses the positive images of a plum, a bright star, and a mountain top as rhetorical devices to help persuade Lucinda to embrace love.