White Pine - An Iconic Sentinel Tree
By Katie Stuart
When you look at many ridge tops around us in northern New England, you will often see conifer trees towering above the canopy height. These are usually white pines, often called sentinel pines. Eastern white pine (Latin name: Pinus strobus which means ‘pine cone') is the largest tree in the Northeast, typically growing 80 to 100 feet in height and two to four feet in diameter. They live up to 200 years or more although some will grow much larger and live much longer. Native Americans found uses for the needles, sap, cones, and inner bark.
Needles made a tea that is stronger in Vitamin C than orange juice and were also woven into baskets; sap was used to seal wounds as it has an antiseptic quality; and the inner bark could be eaten raw although it was more for subsistence. Even today, the needles on the ground can be gathered and used as mulch in gardens. In early colonial times, large white pines were designated on their bark with crowns or the king’s broad arrow as King George claimed exclusive rights to the best of these pines, which were called “King's Pines,” for the British Navy, which was desperate for ships’ masts.
Fast-growing trees of intermediate shade tolerance, white pines have bluish-green soft and flexible needles in bundles of five, giving them a feathery plumelike look in outline compared to other local pines such as the red pine. Each year’s growth is marked by a whorl of branches, and the cones require two seasons to mature. At the end of the first season, cones are upright and about three-quarter of an inch long. They become pendant at the beginning of the second season and grow to a length of four to eight inches and are resinous. Young trees start producing cones with viable seeds at about 20 to 30 years of age. Good seed years happen every three to five years which is a mainstay in diets for many wildlife species including birds such as red crossbills, chickadees, nuthatches, pine siskin, and grosbeaks, and mammals such as snowshoe hares, porcupines, deer, red and gray squirrels, and cottontails. Bald eagles often nest and roost in tall and sturdy white pine trees that protrude above the forest canopy near water bodies, providing easy flight access and good visibility. Bats will also roost and nest in white pines. Like other conifers, white pines provide thermal cover for wildlife in summer and winter.
The seeds gathered and stored by mice, squirrels, and voles are often the source of newly developing pine trees. A recent study published by a University of Maine biologist found that small mammals can play a key role in determining species composition of forests by what they are eating, and this has a large impact on forest regeneration. White pine seeds are important when vole populations are low by helping the voles survive and bear young in greater numbers. Mice also prefer white pine seeds.
In dense forests, white pines “self-prune” and are often clear of branches over the lower two thirds of the trunk, forming tall, straight trees. However, white pines are also early colonizers of pastures, sometimes called “pasture pines” where they have living branches that persist nearly to the ground. These pasture pines can be found on a variety of sites from extremes of dry rocky ridges to wet somewhat boggy areas. Since white pines are sensitive to pollution and road salt, you will often see their needles turn brown from winter road salt.
The wood is easily worked and has been a favorite for construction of all sorts, including furniture, building construction, millwork, flooring, trim and pulp, and it takes stains and paints well. Here in New England, white pines are popular Christmas trees with their feathery foliage that both shears well and holds their needles. The branches of white pine are also used in making holiday wreaths and garlands because of their soft, feathery needles.
You may be aware that pines play a role in helping to combat climate change by absorbing and sequestering carbon dioxide. It is also worth noting that these trees contain compounds associated with its scent which may help cool the climate. A study conducted by the University of Washington found that the gasses released by conifers, including white pines, create particles that promote cloud formation and reflect sunlight, effectively cooling the local atmosphere. The particles released by pines can be large enough to seed clouds, creating shade and encouraging rainfall. One of the authors, Joel Thornton, noted, “It’s thought that as the Earth warms there will be more of these vapors emitted, and some fraction of them will be converted to particles which can potentially shade the Earth’s surface.”
Stately and majestic, white pines bring a tremendous diversity and versatility in providing food and shelter. It is easy to see why the white pine was named Maine’s state tree and the Maine state flower is the white pine cone and tassel. The next time you walk by a white pine, take a moment to appreciate all that this beautiful and elegant sentinel tree brings to our Mahoosuc ecosystem.