Maple syruping at the Minnesota Landscape Arboretum

The second-graders of Expo Elementary School in St. Paul have sophisticated palates, judging from taste tests they performed last week on a field trip to the Minnesota Landscape Arboretum in Chanhassen.

"It tastes like really, really sweet water," said one boy, sipping from a small paper cup of fresh sap collected from the arboretum's maple trees.

A slight exaggeration, maybe — the sugar content of uncooked sap is only about a quarter that of Coca-Cola — but close enough. Fresh from the tree, maple sap more closely resembles the stuff that comes out of a faucet than anything you'd pour on pancakes. (It's worth noting that "maple water" is being packaged and sold as a new product called Vertical Water, described as a refreshing alternative to coconut water.)

Finished syrup, on the other hand, is 66.5 percent sugar, about six times sweeter than Coke. Most of the students could tell the difference between the maple-flavored "pancake syrup" (typical contents: high-fructose corn syrup, cellulose gum, caramel color, artificial flavors, sodium hexametaphosphate) and genuine maple syrup (contents: sap).

Although many kids their age actually prefer the fake stuff, the Expo group seemed to enjoy the real thing, served on a small square of waffle.

"I love waffles," a girl said.

So do a lot of people, apparently. Maple-syrup production is the most popular of all the arboretum's educational programs, said marketing and communications manager Judy Hohmann.

"More and more people are into exploring nature, and seeing how all things fit together," Hohmann said, and learning "that syrup is more than just the product on the shelf at the store."

A classic sign of spring, syruping peaks in March, when temperatures warm up enough by day to send the sap coursing up through the trunks but still dip below freezing at night.

This year's seemingly endless winter has slowed the sap's flow, said Richard DeVries, who runs the arboretum's syrup production. But he's not out to make a killing in the syrup industry; his main goal is to produce enough to serve at the arboretum's annual pancake brunch in March. What's left, he bottles by hand for sale in the visitors center.

This year's brunch fell on a cold day, but about 300 people ventured out to tour the syrup production area. Others attend open houses at the arboretum's Sugar Shack — including one from noon to 4 p.m. Saturday — where they can examine the equipment in which the syrup is gathered and cooked.

"I'm surprised how many people come to the open houses who just have 20 trees or so in their back yard," DeVries said. But one man he knows started out that small and has since expanded his operation to about 1,000 trees and become an expert. "When I have questions, I go to him."

Teaching history, technique

"We have as many sugar maples, but it's just not as big here," he said. "I think it's catching on, though."

Students on field trips hike into the sugar bush and learn how to identify a maple, drill a tap hole and attach a plastic collection bag. Peering into the woods, they can spot elements from various eras of syruping history, from the steel buckets affixed to a few of the trees and an old-fashioned wood-fueled stove used occasionally to cook small batches, to the plastic collection bags still used by hobby tappers, to the contemporary plastic tubes that larger operations use to carry the sap from trees to vats.

On half of the trees, a gravity system pulls the sap downhill; the other half are attached to a vacuum pump, the more efficient method used by today's larger producers.

Once collected, the sap is boiled in big covered tanks until the liquid is reduced to about a 40th of its original volume (the arboretum's trees produce sap with a slightly higher sugar content, so in their case it's closer to a 30th, DeVries said). One Expo girl explained the physics: "If it gets to a really extreme amount of heat, the water would vaporize," she said.

And voilà, tree water becomes waffle-worthy.