The poem's emotional center is Dickinson's relationship with the natural world. She addresses the garden, the bee, the hillsides, the forests—these aren't decorative images but companions she's rambled with (a word suggesting long, familiar wandering). The fear isn't death itself but leaving them behind.
Notice the verbs she can't bring herself to do: tell, name, hint, lisp. 'Lisp' is particularly striking—it suggests childlike speech, something whispered or half-formed. She imagines speaking her death so quietly it barely counts as speaking, and even that feels like too much. The progression moves from deliberate silence ('I have not told') to accidental revelation ('heedless by the way'), mapping every way the secret might escape.
The final image—'One will walk to-day'—is characteristically Dickinsonian in its compression. 'One' could mean her (she'll walk into death) or death itself (it will walk to her). The riddle remains a riddle even as someone walks into it. She never does tell the garden directly; the poem itself is the telling, spoken to us instead of to the hillsides.