A quiet winter scene unfolds in a few lines: a field behind the house, fog moving through branches that have frozen stiff with ice. Nothing happens, exactly. The speaker simply watches, and the stillness feels cold, hushed, and a little ghostly.
The second stanza shifts from the whole landscape to one small plant. The wild mustard has dropped all its seeds, so it stands dry and empty. You might expect that to read as sad or spent. Instead the speaker says it "looks ready for anything." That turn is the heart of the poem. The bare stalk seems unburdened rather than defeated, as if losing its seeds has left it lighter and braced for whatever comes next.
The speaker's feeling seems to be calm admiration, maybe a touch of quiet humor. The mood begins in frozen rigidity but ends in something more alert and hopeful, with a sense that emptiness can be a kind of readiness.