This is a fairly straightforward poem for Emily. She’s writing about how the days are growing more mild and that nature is adorning itself with colorful leaves and so she too has decided to ornament herself, unlike in winter when all a person can do is bundle up in drab, but practical clothes against the cold.
The most interesting line, for me, is “The Rose is out of town”. I admit I had to look up when roses typically bloom (a few weeks into spring) and then I realized that she’s probably plucked a few of these roses and they are sitting in a vase decorating someone’s open window to let the fresh spring air in after a long, dreary winter.
Emily is also writing about how she is transforming in accordance with nature. During the winter the “morns” are harsh, the “maple” wears no scarf, and the “field” is barren or buried under snow. In other words, winter is old fashioned in that it’s the end of the year (think old man winter) and is, from a fashion sense, literally ‘out of season’ once spring comes around. But as the “nuts are getting brown” and the “berry’s cheek” grows more plump, she too is transformed by putting on a colorful bracelet, or perhaps some flowers in her hair, because that is nature’s way. She recognizes that we are natural beings (sexual even) who are part of this mortal realm and so we should act in accordance with nature.
Life doesn’t have to be an endless season of dreary spiritual servitude. God commanded that we be fruitful and multiply, and so Emily is complying with God and with nature.