Thoreau writes in his journal:
P.M.—To Walden in rain.
A May storm, yesterday and to-day; rather cold. The fields are green now, and the cows find good feed. The female Populus grandidentata, whose long catkins are now growing old, is now leafing out. The flowerless (male?) ones show half-unfolded silvery leaves. Both these and the aspens are quite green (the bark) in the rain . . .