Lines 25-28 Summary

Get out the microscope, because we’re going through this poem line-by-line.

I feel that I would like
to go there

Our speaker wants to go to the place her son described. Hey, we wouldn't mind a visit either. It sounds lovely, and it's not that strange to want to go somewhere that someone has described to you.
But it is perhaps a little strange that she wants to go here, given that her description of this place sounds rather similar to her description of her own yard (the heaviness, the trees with white flowers).
She's feeling pretty uninspired by her own place, yet is open to this other one?
It's also worth noting that this is one of the few places in the poem where the widow tells us how she feels. She doesn't say, "I would like." No, instead she says, "I feel that I would like." She seems a bit unsure of herself, doesn't she? She's somehow distant from her own desires.

and fall into those flowers

On the most basic level, this line tells us that the widow would like to fall into the flowers out in this place her son told her about.
Doesn't she have flowers (white ones even!) on her plum tree right there in the yard? Why does she want to go all the way out to the meadow? Why do these flowers draw her more than the ones that are a few steps away?
And what is it about them that makes her want to fall into them?

and sink into the marsh near them.

Apparently our widow doesn't just want to fall into those flowers. She also wants to sink into the nearby marsh.
Hey, maybe she just likes to paddle around in marshes. Maybe it makes her feel better.
But we can't deny that there's a definite suggestion of suicide here. Especially with that word "sink." Marshes, after all, are filled with water. So we have to ask: does she want to drown?
When we think about it, a suicidal desire, sadly, doesn't seem out of left field. It's a pretty heavy and all-encompassing sorrow that our speaker has been expressing throughout this piece. Her husband is dead. She's pretty much all alone in the world.
Still, if we wanted to put a positive spin on it, we might say that maybe sinking into the marsh is her way of reuniting with the world she has become detached from.
She used to find joy in the natural world. Now she doesn't. But by sinking into that marsh, maybe, just maybe, she would be reunited with the natural world she has lost.
Unfortunately, as with much of the poem, our widow-speaker doesn't come right out and tell us what she means.
Even at the point where she longs for death (possibly), she's still pretty reserved. This is not a woman who relishes share-time.
Whew. What an ending, right? Talk about haunting.