The Year's Awakening

How do you know that the pilgrim track
Along the belting zodiac
Swept by the sun in his seeming rounds
Is traced by now to the Fishes' bounds
And into the Ram, when weeks of cloud
Have wrapt the sky in a clammy shroud,
And never as yet a tinct of spring
Has shown in the Earth's apparelling;
O vespering bird, how do you know,
How do you know?

How do you know, deep underground,
Hid in your bed from sight and sound,
Without a turn in temperature,
With weather life can scarce endure,
That light has won a fraction's strength,
And day put on some moments' length,
Whereof in merest rote will come,
Weeks hence, mild airs that do not numb;
O crocus root, how do you know,
How do you know?