Over the past two weeks, consecutive snowfalls yielded breathtaking sights in our landscape, as noted by Arboretum Director William (Ned) Friedman and visitors who enjoyed sledding, skiing, and strolling in the wintery wonderland. However, heavy snows can be harmful to some of our plants, causing structural failure and branch breakage. In particular, the snowstorm on February 8 did an astonishing amount of damage, with approximately 150 plants requiring immediate attention after the storm. This number is astounding when compared to last winter, when we saw minimal plant injuries despite the eight to nine feet of snow covering the Arboretum grounds. So why did this one storm cause so much damage? The answer lies in the specific characteristics of the snow and weather conditions that accompanied it.
February 8 delivered six to eight inches of snow in Boston. The temperature hovered around 34F degrees, resulting in an extremely wet, heavy snow. While the dry, fluffy snow that falls at cooler temperatures can serve as an excellent insulator for the soil and protect fragile roots from freezing, snow with a higher water content is much denser and heavier, and its weight can threaten the integrity of tree and shrub branches. This heavy, slushy mix covered our plants continuously through the day, adding more and more weight to branches and treetops. Additionally, the lack of wind during the storm gave the plants no chance to shake off some of the excess snow. Under the heavy accumulation, the thinner ends of many branches snapped off. The snow also followed a period of heavy rain and warmer-than-average temperatures, rendering the ground softer than usual and giving less support to root systems. This caused some trees to simply fall over under the enormous pressure of the snowfall. Others had their top branches split open, and some shrubs were flattened. The plants that suffered the most damage included white pines, crabapples, birches, maples, ponderosa pines, pear trees, and more.
The breadth of damage triggered an immediate response from Arboretum horticulture, arboriculture, greenhouse, and curation teams that Curator Michael Dosmann dubbed Tree Triage. The horticulture crew’s first priority is to remove anything from the landscape that could be hazardous to visitor safety, like weak or split branches. Then, the horticulturists and arborists record information about each damaged plant, sending the reports to the curation team. Plants that have suffered minor to moderate breakage but can recover are marked for extra care and support, while those that are completely shattered and may not recover present a more urgent case. In those cases, an immediate request to re-propagate the plant is sent to the propagation team at the Dana Greenhouses, who take cuttings or propagules of the plants in decline and initiate the process of growing a new plant—a process that can take up to seven or eight years until the new plant is ready to grow in the landscape. These re-propagation efforts are particularly important for plants that are rare, historic, valuable, or horticulturally unique, such as a white cedar (Thuja occidentalis) on Peters Hill, a wild-collected plant and the only one of its species in our living collection.
With one of the most comprehensive and best documented living collections of woody trees, shrubs, and vines in the world, the Arnold Arboretum follows rigorous protocols to protect our accessioned plants in the face of weather challenges. Our teams are committed to doing everything possible to maintain valuable lineages of rare and important plants, both to support botanical research and to preserve critical examples of temperate biodiversity.
You can help the Arboretum respond to storm damage and support the ongoing care of our plants and landscape by making a gift to our Living Collections Fund.