Wow, that Heaney poem has got some juicy language! So much fun to read out loud. I think the Heaney poem could be read as a critique of the platonism/gnosticism of the sonnet.

I loved your analysis of all the things that cut off in the poem. I'd just add that it's pretty rare to come across a poem where you transition from summer to winter. If fall was in there, we'd have this smooth passage of time, but instead we just go from trees with leaves to bare bark (that reminds me of dc).

"But flowers distil'd though they with winter meete/ Leefe but their show, their substance still lives sweet."

There's a major devaluation of materiality here. The petals and the stem are just for show; they're just a casing for essential flowerness. And through a distillation process, it's possible to free the wheat from the chafe and preserve the eternal form of flowerhood without the flower.

In Heaney's poem, the narrator reacts to abundance with this "hunger" that sets him out into the briar with pales. But "once off the bush the fruit fermented." In the sonnet, it was only when the essence of the flower was removed from the material plant that the value could be preserved for eternity, but in Heaney, value imbues the physical IN TIME, and the attempt at abstraction (distilling a blackberry bush into a consumer product) causes decomposition and devaluation.

Let me add my own passage into the conversation. It's my favorite passage from an essay by Marilynne Robinson:
"One might as well say that the earth invades the seed, seizes it as occasion to compose itself in some brief shape. Groundwater in a sleeve of tissue, flaunting improbable fragrances and iridescence as the things of this strange world are so inclined to do. So a thriving place is full of intention, a sufficiency awaiting expectation, teasing hope beyond itself."