The tallest tree at the Arnold Arboretum isn’t a majestic white pine or a venerable beech, it’s a silver maple (Acer saccharinum, accession 12560-C). This stately 127-year-old specimen was recently measured at 126 feet (38.5 meters) tall. Its DBH (diameter at breast height) is currently 67 inches (170 centimeters); it takes three people, fingertip-to-fingertip, to encircle the trunk. This tree started its life at the Arboretum in the form of seeds (accessioned under the then-accepted name Acer dasycarpum) received from the nursery of Benjamin M. Watson in Plymouth, Massachusetts on June 1, 1881. Two other silver maples from accession 12560 also lived at the Arboretum for over 100 years, but specimen A was removed in 1982 and specimen B was removed late in 1985 after suffering major damage from the winds of Hurricane Gloria.
Acer saccharinum 12560-C displays the typical form of a mature silver maple: a massive trunk that soon divides into multiple upright limbs; thin, pendulous young branches curving up at the tip; and a rounded, spreading crown. The mature bark is characteristically gray-brown, ridged, and scaly. On this tree (and many other old silver maples) the curving bark scales appear to spiral up the massive trunk. The textured bark and impressive girth of Acer saccharinum 12560-C are irresistible to many visitors passing by on Meadow Road; no doubt this is one of the most frequently touched trees in the Arboretum.
Acer saccharinum is native to moist woods and river bottoms in much of the eastern half of the United States and a fringe of southeastern Canada. It can grow in drier soils, but may not be as successful or long-lived. Charles S. Sargent noted in Silva of North America, “On dry and elevated ground…” silver maple “…is not handsome…the habit is loose and unattractive….” No doubt the vigor, longevity, and stature of Acer saccharinum 12560-C is due in part to its ideal growing site in the moist, rich soil of the Arboretum’s Meadow area.
Silver maple is often considered highly susceptible to storm damage, but Acer saccharinum 12560-C has survived many storms—including the devastating hurricane of 1938—with little damage. Along with other large, old trees at the Arboretum, this specimen is inspected regularly by staff arborists. In 2006, Acer saccharinum 12560-C was tested using radar imaging and wood density borings in addition to visual inspection. The tree proved to be amazingly sound for the most part, but the presence of some decay led to a bit of support work; two cables now connect several of the main vertical limbs, which should help reduce the chance of major limb breakage in high winds. As with most mature trees at the Arboretum, pruning on Acer saccharinum 12560-C is limited to removal of dead wood. To reduce soil compaction (from its many up-close admirers), mulch is spread in a wide swath around the tree and the soil is periodically loosened with a compressed-air tool.
Silver maple’s popularity as a shade tree has waxed and waned over the decades. Its status as a native plant and its ability to grow quickly in a wide range of soil conditions gave rise to widespread planting in some eras. However, it has just as often been shunned for its irregular trunk habit, susceptibility to storm damage, extensive root system, and prolific seed production. Silver maple is not a good choice for small urban lots or narrow planting strips along streets, but in larger sites such as parks its leafy, shade-casting canopy is an asset. Acer saccharinum 12560-C certainly shows that silver maple can be a beautiful and impressive tree in the right setting.
Nancy Rose is editor of Arnoldia.