While she’s writing mostly about looking at the flowers and being filled with “contra” feelings: joy (“transport”) and perhaps grief (“trouble”), these flowers could stand in for people too, especially the soldiers who were still heading off to fight in the (US Civil) war. The image of the “Daisies” that “blow” upon the hillside reminds me of a bugle and a cemetery for the fallen boys.
The word “Well” in the first line is an unusual word choice. At first glance it has the affect of her being unsure about what she wants to say or what she is actually feeling. This is supported by the third line where she describes how the flowers can “transport” her but also “trouble” her and she’s having a difficult time reconciling these “contra” emotions.
But the word “Well” alludes to so much more than indecision. In the previous poem, “Have you got a Brook in your little heart“, she might be talking about the act of writing (creating art) and her “Brook” is the ink which flows from her pen. Thus the “Well” here might be the inkwell which holds the potential for her with which to draw upon and write a poem. When combined with the possibility that she is uncertain about her feelings, this usage of the word could be her calling out to her “Well” for some inspiration. The word is separated by two dashes as if she needs to address this “Well” individually and specifically from the rest of the line.
To continue down the well (pun very much intended), she is plumbing the depths of her feelings about these flowers (or her own poems if we take flowers to mean her poems) and what she sees in the well is not only the water one needs to survive (previously she wrote of her “little brook of life“) but that the well from which one draws upon is also an uncertain place, a literal hole deep in the ground, a portal to the afterlife of which the dead travel. The idea of the earth giving and taking life is common in her poetry and in this poem she connects the image of water to ink (‘fountain”), her emotions to a well, and thus is confused by how her emotions compete within her for what these flowers / poems mean: are they beautiful, are the troubling?
My footnote states that this is one of her published poems in the publication Drum Beat on 2 March 1864. Drum Beat raised money for the Union Army so parents and soldiers would have been aware of it and what was published inside would probably have been articles, stories, and poems that glorify the boys going off to war, celebrate the survivors of battles, remembrances of those who fell in battle, and otherwise content which would soothe and bring contentment to worried parents and soldiers. Yet Emily’s poem is one filled with uncertainty which is often the biggest enemy to a soldier in battle. Not knowing if the flowers are beautiful or not could mean the flowers will either adorn the victorious in battle, or adorn their graves after the battle. For a young person to read this before heading off to war might leave someone unsettled.
Her line “Too much pathos in their faces” might then not only refer to her looking at the blossoms of the flowers, but of the boys as they march off to what could be their doom and she is unable to look at them without feeling conflicted: she wants to celebrate these young men, but she also knows they might not be coming back and is saddened. Thus she wishes to be more simple like the “Butterflies from St Domingo” who don’t trouble themselves with such complex emotions and only see the good and the beautiful.
But I believe she is also, once again, writing about writing as she did in the previous poem, yet here she understands that her art is both beautiful but also troubling and that she might wish she could just write something nice to placate the readers of a publication like Drum Beat. But she can’t because her “breast” (her heart) is too simple because it feels too much (and is thus not simple, hence the contradictory feelings that live in it) and thus is a “Well” filled and almost overflowing with the waters (emotions) of uncertainty. In other words, she sees something so beautiful that it makes her cry.