Sugar Maple

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Seeing the Forest Through its Trees Part XIV

By Larry Ely

Sugar maple (Acer saccharum) grows in abundance in Maine and New Hampshire and is one of three common tree species including beech and yellow birch that define the New England northern hardwood forest. Under this forest, ephemeral plants such as red trillium and Canada mayflower live their short lives beneath the open canopy in the brief season between loss of snow cover and full leaf cover.

Leaves of shade-tolerant sugar maple and beech control light reaching the forest floor in late May to early June and limit growth of other tree species. Sugar maple seedlings survive in the low light, biding their time until a canopy opening allows them to thrive. Their efficient leaves can photosynthesize with as little as 25 percent daily sunlight, allowing the species to reproduce in the shade and maintain a climax community for a long period.

Sugar maple prefers enriched, moist soils of well-drained uplands and valleys and on those sites may reach 200 to 400 years of age and grow to 60 to 70 feet in height in our region. The bark of the young tree appears smooth like red maple, though a rough texture can be felt. Light gray bark of the young tree becomes deeply furrowed and light to darker gray as it matures. The three to five inch-long leaves with three to five pointed lobes are separated by a smooth “U” shaped margin between lobes, unlike the similar leaf of the red maple which has serrated margins ending in a “V” shape. In the open, the tree’s trunk supports stout erect branches with a rounded top. In a closed canopy forest, a shallower top develops over a trunk which has lost half of its lower branches through self-pruning.

Sugar maple’s wood is close-grained, strong, and hard - often also called rock or hard maple - and is used for furniture making and flooring among many other uses. It is considered New England’s finest firewood and burns slowly with long lasting, glowing coals and is a favorite to add to the wood stove for an overnight burn.

5-lobed sugar maple leaves in the fall. Photo by Larry Ely.

Native Americans obtained sweetener from sugar maples by slashing the bark to promote sap flow that was allowed to freeze and concentrate sugar, followed by boiling in a wooden trough by dropping in hot stones. Colonial settlers captured the sap in metal pots for boiling. A single tree can produce 5 to 60 gallons of sap in a season, and 32 to 40 gallons are needed to produce a gallon of syrup. Today, commercial “sugar-bushes” use a system of tubing throughout the forest that has sap flowing to a central point for boiling at a sugar house. Sap flow requires warm, sunny days in early spring with sub-freezing night-time temperatures near 20 degrees Fahrenheit, and those days now arrive earlier each year.

In fall, the glorious sugar maple stands out with an array of leaf colors of scarlet red, orange, and yellow. A single tree may have some leaves turn scarlet while others on the same tree might turn yellow or orange. Other trees might produce all bright clear yellow leaves, and it is not unusual to see a fully green sugar maple with a single branch bearing brilliant red leaves.

Sugar maple seeds are spread by winged samaras, and in winter migrating evening grosbeaks feed on seeds still on the tree while nuthatches, finches, squirrels, chipmunks, and mice also feed on those found on the forest floor. Red squirrels use their incisors to gnaw a wound in the tree and return to feed on the sugars after the sap has concentrated through freezing.