Blackberry picking sounds simple, but the speaker shows how much awkward, hard-won skill it takes. You learn to lift your feet high and slow like a heron, to back out through the canes in heavy boots, and even to lean into the worst thorns "nimble as a lover" in order to get loose. The speaker admits these skills aren't much use elsewhere, with a dry, humble humor.
Then the poem turns. After the sweat dries and the mosquito's whine fades, a quieter moment arrives. You reach for one last sweet berry and your hand won't move. The poem doesn't say why, but it suggests the body has reached a limit, perhaps tiredness, age, or something less easy to name. The final line, "wondering why in hell," carries surprise and a little frustration.
The mood begins playful and physical, then settles into stillness, with a hint of unease beneath the sweetness. Reaching for that last berry feels like reaching for anything we want but can't quite get.