WILLIAMSTOWN - Bob and Margot Sanger began tapping the sugar maples on their Cole Avenue property several years ago at the suggestion of a friend.
"I didn't even know we had sugar maples," said Mrs. Sanger, who now can identify the slightly shaggy-barked trees on sight, and has become something of an expert at backyard sugaring.
Last weekend, four big pots containing maple sap boiled away on two Coleman burners in her garage well into the evening.
Each year during sugaring season, which usually begins in mid-February and lasts until the buds form on the maples, the Sangers harvest enough sap to give to friends and relatives during the holidays and to use for cooking.
The three large sugar maples in their yard are around 110 years old, as are many other sugar maples in town. (Mr. Sanger approximated their age by counting the rings of a neighboring pine tree that had to be cut down and which was of the same vintage.)
As with many sugar maples, the Sangers' likely served as landscaping features, and to define property boundaries.
Colorful foliage in the fall and the broad shade they offer in the summer make sugar maples desirable for yards and parks. And of course, early March brings the initial thaw that allows for the harvesting of maple sap.
"We talked our neighbor into it," Mrs. Sanger said. "I spent two years working him, badgering him, because he has seven trees. So this year I convinced him." Mr. Sanger placed the taps for the neighbor and offered advice about evaporation - a process he and Mrs.
To shorten the overall evaporation time, they warm the syrup in a microwave oven before adding it to the pots. The sap is transferred down the line of pots, becoming more and more concentrated along the way - a method that allows for a steady, constant flow and prevents crystallization.
True syrup is at least 66 percent sugar. Sugar content can be determined by using a hydrometer, which measures buoyancy, or by using a regular thermometer, since the known boiling point of syrup is 219 degrees Fahrenheit.
Mrs. Sanger has discovered that unbleached muslin provides the best filter to catch any grit that might come off the trees or blow into the buckets. "It's a delicate process," she said. "Syrup can curdle just like milk if you're not careful."
The Sangers ordered bottles in the shape of maple leaves and "Sanger Syrup" labels to put the finishing touches on their backyard harvest, which has become a family tradition.