in Thoreau’s Journal:

Now is the season of the leafing of the trees & of planting. The fields are white with houstonias as they will soon be yellow with buttercups.

Perchance the beginning of summer may be dated from the fully formed leaves—when dense shade? begins—I will see. High blue berries at length. It is unnecessary to speak of them. All flowers are beautiful….A ladies slipper well budded and now white.