Watertown Commission Approves Chemical Knotweed Treatment at 99 Coolidge Site

WATERTOWN — June 3, 2026 — Watertown Conservation Commission unanimously approved a chemical-and-mechanical knotweed removal plan and received a detailed carbon study estimating Whitney Hill Park's forest holds roughly 2.4 million pounds of carbon. The commission voted to allow direct herbicide application — using a diluted, wetlands-approved glyphosate formula applied by licensed applicators to cut stems — at the 99 Coolidge Avenue stream corridor after years of unsuccessful mechanical-only removal, with at least three to five growing seasons of treatment planned under the order of conditions valid through April 2029. Bob Leverett of the Minerva Action Group, co-founder of the Native Tree Society, presented findings that the park's roughly 10 acres of forest are adding approximately 32,000 pounds of new tree carbon each year, equivalent to about 4,800 standard tons of carbon dioxide equivalent in total storage. Member of the public Libby Shaw, president of Trees for Watertown, urged the commission to use the data to advance a tree protection ordinance, noting Cambridge and Somerville have adopted similar policies. The commission also closed out the order of conditions for a completed multi-use bike path connecting the 99 Coolidge site to the DCR path at Arsenal Street.