Final answer:
The speaker is comparing dormant seeds under the soil in winter to corpses in graves, highlighting their inactive state similar to death, awaiting spring's warmth to germinate.
Step-by-step explanation:
The speaker in the poem is literally referencing the physical state of the seeds during the winter. When they mention 'winged seeds' that 'lie cold and low, Each like a corpse within its grave,' the speaker is drawing a comparison to how seeds remain dormant beneath the soil during the cold season, much like a body lies in a grave. This metaphor highlights the inactive and lifeless nature of the seeds awaiting the warmer conditions of spring to germinate and grow, which can be likened to a form of rebirth or resurrection.