What Thoreau Said: Am struck by the beauty of the yellow birches, now fairly begun to be in bloom, at Yellow Birch, or Botrychium, Swamp. It is perhaps the handsomest tree or shrub yet in bloom (apparently opened yesterday), of similar character to the alders and poplars, but larger and of higher color.
-- May 5, 1859
You see a great tree all hung with long yellow or golden tassels at the end of its slender, drooping spray, in clusters at intervals of a few inches or a foot. These are all dangling and incessantly waving [in] the wind, â a great display of lively blossoms.
Birch trees are flowering an average 5 to 10 days earlier now than when Thoreau noticed them, Primack and Miller-Rushing found.