Somerville's Relaxed Approach to Invasive Plant Rules: What's Allowed

If you live in Somerville or are thinking about moving there, invasive plant rules are one of those things you probably won't think about until they affect you directly. Somerville has 2 specific rules on the books covering different aspects of invasive plant rules, and some of them might surprise you.

Prohibited Species

Somerville bars the city from including any invasive plant in its own plantings under Code Sec. 12-176. The rule covers new trees and plants the city or its contractors install, not existing landscaping or private yards.

Key details: Governing section: Code Sec. 12-176. Adopted: Ord. No. 2021-05, March 25, 2021. Scope: City and third-party plantings only. Excluded: Existing trees/plants, private property. Native minimum, parks: 75% of new plantings.

The ordinance is a planting standard for city projects, not a citation scheme against residents. Compliance runs through the director of public space and urban forestry and the senior urban forestry and landscape planner, who oversee city and third-party plantings and file the annual report required by Sec. 12-180. A city department that fails to report its plantings by December 1 falls short of its obligation under that section, and a contractor planting an invasive species on the city's behalf on covered property is out of compliance with Sec. 12-176.

The rules around prohibited species in Somerville lean permissive, but that does not mean anything goes.

Tree-of-Heaven Removal

Somerville's tree ordinance singles out Tree of Heaven (Ailanthus altissima) for exclusion: unlike other invasive species, it never qualifies as a protected "significant tree" no matter its size, so removing one requires no tree permit under Sec. 12-102 and Sec. 12-112.

Key details: Governing section: Code of Ordinances Sec. 12-102. Species excluded: Tree of Heaven (Ailanthus altissima). Other invasive threshold: 24 inches DBH triggers protection. Tree of Heaven threshold: None; never protected. Enacted: Ord. No. 2025-05, 5/8/2025.

There is no permit requirement, fee, replacement obligation, or fine tied to removing a Tree of Heaven, because Sec. 12-102 excludes it from the definition of "significant tree" that triggers Sec. 12-112's removal permit. By contrast, removing a protected significant tree without a permit exposes a property owner to the tree preservation article's $300.00-per-offense fine under Sec. 12-113.

Somerville is more permissive than most cities when it comes to tree-of-heaven removal. That said, there are still limits.

The Bottom Line

Compared to many U.S. cities, Somerville gives residents more room on invasive plant rules. 2 of the 2 rules here are rated permissive. But permissive does not mean unregulated. There are still requirements, and the city does enforce them when violations are reported.

These rules come from Somerville's publicly available municipal code. For complete penalty schedules, exemption details, and answers to common questions, see the individual ordinance pages throughout this guide.