What does the poem "Pink, Small, and Punctual" by Emily Dickinson mean?

This nature riddle by Emily Dickinson was published in The Complete Poems of Emily Dickinson in 1924, and in that version, the answer was provided beneath the poem in parentheses. The poem describes a spring wildflower known as the mayflower trailing arbutus. This low plant is now a protected species in many states because it has become very rare. 

Let's look at Dickinson's clues to solve the riddle. "Pink": the flowers of this plant are either pink or white. "Small": Each flower is only about half an inch wide when fully opened. "Punctual": The flowers are known as "mayflowers" or "Puritan mayflowers" because they were the first flowers that greeted the Pilgrims after their first difficult winter in Plymouth. "Punctual" compares them to guests who are the first to arrive at a gathering. "Aromatic": The flowers are known for their exquisite fragrance. "Low": The plants grow only about 4 to 6 inches high. "Covert in April": The plants first spring up under fallen leaves where they can't be seen. "Candid in May": Dickinson plays on the meaning of candid, which can mean frank and open. They reveal themselves, thus being "frank," and they are "open" both in the sense that they are out in the open, having grown up above the leaves that hid them in April, and the flowers open in May. 

"Dear to the Moss": Dickinson may mean that the flowers hug the moss, which also grows low to the ground, or that the arbutus feeds on a specific type of fungus, so the "moss" or fungus is feeding the arbutus like a nursing mother. "Known by the knoll": probably refers to the arbutus trailing along a hillside. "Next to the robin in every human soul": Just as everyone rejoices at seeing the first robin because it heralds the springtime, so these little flowers signal the beginning of the warm weather and rebirth of nature. "Bold little beauty": The pretty little flowers are brave to be the first to show themselves after the winter. "Bedecked with thee Nature forswears Antiquity": Nature denies how old it is by putting on these flowers. When Nature dresses up with arbutus flowers as its necklaces, it looks young, and one would never guess that it is as old as the world. The reference to antiquity may also bring to mind the plant's history with the Pilgrims. 

This flawless and charming riddle by Dickinson shows the delight she had in nature--a delight modern readers can share through her witty and masterful way with words.