in Thoreau’s Journal:
The red maple sap, which I first noticed the 21st of February, is now frozen up in the auger holes, and thence down the trunk to the ground, except in one place where the hole was made on the south side of the tree, where it is melted and is flowing a little. Generally, then, when the thermometer is thus low, say below freezing point, it does not thaw in the auger holes. There is no expanding of buds of any kind, nor are early birds to be seen. Nature was, thus, premature, anticipated her own revolutions with respect to the sap of trees, the buds (spiraea, at least), and birds. The warm spell ended with February 26th.