Reading Michael Field's "Unbosoming," I notice that the word "its" in line 12 is ambiguous. On the one hand, it could be referring to the narrator's "breast" (line 11); on the other hand, it could refer to the "[quivering] bloom" mentioned in line 9, which is the bloom of the "iris" (line 3). If one uses the former definition of "its," the result is that the "burden and strain" are on the "contents" of the woman's breast, one of the very cores of her sexuality (i.e., the woman is quite literally carrying in front of her the burden of her socially unacceptable secret: she is homosexual). If one uses the second definition of "its," the result is that the BLOOM'S contents PUT "burden and strain" on the woman's breast. The difference is subtle, but it changes the poem significantly, suggesting that the bloom itself has "great content," and the woman's breast does not (necessarily).
Paradoxically, these two approaches take the reader, in two different ways, to (nearly) the same place/conclusion: (homosexuality) the love that the woman carries is oftentimes a burden. One can regard this burden as being feminine, no matter which reading of the word "its" one uses (and here, I do not mean to invoke the social construct that homosexuals, even men, are feminine/effeminate). On the one hand, the burden comes directly from a woman's body; on the other hand, it comes from a flower, which denotes a degree of gentleness, and perhaps even fragility, that one often associates with women (especially, given the historical context of female oppression). Society often sees women as the weaker sex, and, therefore, the passive, measly flower becomes a symbol for women. In the context of this poem, however, the words "seeds," "flowered," "push," "riot," "squeeze," "clip," "bloom," and "zephyr" (among others) show the iris as a symbol for fertility, reproduction, and other concepts associated more closely and consciously with women than men. The iris, then, is a sex symbol for love between two women. As for the title of the poem, it reminds one of deconstructionist analysis in that the poem is subverting notions about relations between women, and it is also a way of disclosing and, thus, releasing (from her chest) the narrator's secret. Using our Donald Hall reading on queer theory, we can apply many of the key principles to this poem, especially the 2nd, 7th, 8th, 9th, and 10th principles (Hall 236-243).
Finally, it is also interesting to me that one never really finds out what is inside the "heart" of the "bloom." The bloom/iris, thus, becomes a "McGuffin" (for those of you who have studied Hitchcock); ultimately, it does not matter what is in the bloom, because the real issue comes in the final 6 lines of the poem (the issue of secrecy/fear in the context of homosexuality).