And the mold sang in the bleached valleys under the rose. (9)
The rose is a common symbol of love (if you don't believe us, take a good look around next February 14th). But here, our attention is drawn not to the beautiful rose, but rather to the "mold" singing underneath the rose. Roethke doesn't focus on the socially accepted, stereotypical symbol of love. He wants us to look elsewhere at something not usually associated with love or beauty at all.
Over this damp grave I speak the words of my love: (20)
There's an element of conflict in this line. The setting seems to be fighting with the content. Can't we all just get along? When we think about someone speaking words of love, we usually don't picture them next to a grave. A nice restaurant, the deck of a cruise ship— these are the kinds of places for declarations of love.
I, with no rights in this matter, Neither father nor lover. (21-22)
The sense of conflicting ideas and emotions continues in these lines. The speaker declares his love in one line, and then says he has no right to this love in the next. Do you think the speaker really believes that he has "no rights" in the matter or is he just caving in to societal expectations?