The first signs of spring are very sweet, literally. It's maple syrup season and I'm just back from a friend's sugar bush near Lake Superior where we tapped trees in the deep, quiet, snowy woods.

At this time of year, you get a whiff of maple on the bright, damp spring air as the sap simmers into syrup. A group of us gathered to help schlep buckets of sap, collected from taps under the tress, to the huge pot set over a fire. We took turns stirring, while sipping maple-spiked coffee, cocoa and whiskey, stamping our feet to stay warm.

Maple is North America's most reliable indigenous sweetener. Sap is clear, mildly sweet, and runs when the day's temperatures rise above freezing and then drop back down at night. The season begins in March and, most years, continues for about a month. Given our winter, this promises to be a very good year.

It takes about 40 years for a tree to mature and produce sap, and about 45 gallons of sap to produce a gallon of syrup.

The process of reducing the liquid to a thick, glossy syrup is simple. The first run of sap boils down to be relatively light and clear before the rush of starches have begun pulsing through the tree. As the season progresses, the syrup becomes darker, until the last run is as dark as wet tree bark.

Maple syrup, once opened, is best kept in the refrigerator or it may turn moldy. Glass containers maintain the pure taste better than do plastic and metal. If mold develops, strain it out, bring the syrup to a boil in a saucepan, then cool and refrigerate.

Several years ago, the U.S. Department of Agriculture adapted a grading system that relates to color and taste:

Golden: Light and translucent, this syrup is delicate and subtle. Save this for fluffy waffles, crêpes, vanilla ice cream, foods that don't compete with its pure favor.

Amber: This is the familiar maple syrup, sturdy and predictable. It's the syrup for hearty pancakes and bacon, bourbon cocktails and glazes. Its flavor comes through, but does not overwhelm.

Dark: This is the strong stuff, perfect for a barbecue sauce, New England baked beans, and to brush on a slow roasting duck or pork shoulder roast. It makes a wonderful alternative to molasses in ginger cookies and breads.

Beth Dooley is the author of "In Winter's Kitchen." Find her at bethdooleyskitchen.com.