Neruda's poem is one of love and romance, incredulity playing in the author's tone as he praises his love for seeing beyond his faults:
"How you must have suffered getting accustomed to:me,
my savage, solitary soul, my name that sends them all running."
Even as he continues in his expression of love for the woman with various lines, it becomes clear that his own disdain for himself taints this love. "You are like nobody since I love you" weighs heavily with a double entendre--it can be read to mean that no one is as beloved as she, and therefore she is one of a kind; or it can be read to mean that she is nobody because of his love in specific. In other words, his love for her makes her unexceptional. This theme continues when he states, "I love you, and my happiness bites the plum of your mouth." Here it becomes evident that he possibly sees his joy at his love for her as possessive and unobliging--he takes from her naturally and perhaps a bit viciously, as one might bite into a plum.
However, the tone lightens nearer to the end, and it becomes clear that all the comparisons he makes--an allegory with the woman as a lush, fertile, sweet fruit which he enjoys as Nature would have him--are only to indicate what he wishes to provide for her in turn. "I want/to do with you what spring does with the cherry trees" conveys his desire to be part of what makes her flourish, to watch her blossom and bloom under his touch despite his own opinion of his worth.