Snow Or Snowdrops?

Is it snow or snowdrops' shimmer Whitens thus the bladed grass, With a faint aërial glimmer,-- Spring or winter, which did pass? For the sky is dim and tender With an evanescent light, And the fading fields are white, White with snow or snowdrops, under The fair firstling stars of night. Little robin, softly, cheerly Piping on yon wintry bough, Why have all the fields that pearly Iridescence, knowest thou? Did old Winter, grim and hoary, Aim a parting dart at Spring As she fled on azure wing, Or did she with rainbow glory In his face her snowdrops fling?