https://bygl.osu.edu/node/2091
Midwinter cold got you down? With daytime high temperatures above 32 degrees F, and nighttime lows below 32, now is the time to consider tapping Maples. Most commercial maple syrup producers have begun or are in the midst of tapping maples. At one time, the thought was to only tap Sugar Maples because they tend to have a higher sugar content in the sap, usually between 2 and 3 %. But there is a growing interest to tap Red Maple, Black Maple, Norway Maple, and Silver Maple which can have sugar contents ranging from 1 to 2 %. The lower the sugar content, the more sap is required to make syrup and the longer it can take to boil.