How does the rhyme and metre contribute to the meaning of Hardy's "The Spell of the Rose", especially to the use of the eponymous rose and the dialogue structure?

The rose of the title represents the love the husband never "planted" or nurtured in his relationship with his wife. His wife finally plants the roses (which symbolize love) that he promised, but she plants them too late. By the time the rosebush blooms, she is dead, and the husband is left with his regrets.
The rhyme scheme is regular, with the second and third words and the fifth and sixth words of each stanza rhyming, creating a singsong effect. The meter is also childlike and singsong, reinforcing the nursery rhyme-like voice of the speaker. Lines vary between six and eight beats. However—and this is where the meter gets interesting—it is also slightly "off." The beats vary from line-to-line, and some lines fall oddly flat (listen to it read), reflecting the something that is off-balance in the relationship.
This off-kilter relationship is also reflected in the dialogue. The opening stanza repeats the statement—the spoken words—of the husband saying he will build a hall and plant roses for love, but his words, after all, are not entirely true: he never does plant the all important roses, leading to "blight" in the relationship. In the fourth stanza, there is more "dialogue." But this too is a bit off-kilter. The wife talks, but to herself, creating a monologue rather than a conversation with her husband.
The literary devices in the poem, including the dialogue and the off-balance meter within the sing-song nursery rhyme structure, reflect the less-than-ideal relationship Hardy depicts.