On March 24, 2025, Arlington’s Select Board voted to sign on to the Mayors' Monarch Pledge, an initiative that increases natural habitat and biodiversity and helps support monarch butterfly populations across town. The volunteer group Arlington MA Invasives (ArMI) brought the Pledge to the Select Board with the support of Arlington’s Department of Planning and Community Development (DPCD). Among other actions, community members are invited to help support monarch populations by removing black swallow-wort, an invasive plant that is poisonous to monarchs.

Over the spring season, supporters and the Town have been working together to achieve the actionable items listed in the Pledge, which include: 

• Hosting milkweed & other native seed & plant giveaways, swaps, & sales. 
• Planting milkweed and pollinator-friendly native nectar plants along roadsides, medians, or public rights-of-way.
• Continuing invasive species removal (especially black swallow-wort) to prevent caterpillar deaths and support the re-establishment of native habitat. 

Efforts to accomplish Arlington’s commitments include the ArMI-coordinated Adopt a Jug program in which residents grow native species in jug containers and transplant them in Town rain gardens and at various locations across town. Planting native species in this manner helps increase habitat diversity and provides other benefits to wildlife. It also helps build a climate resilient local ecology, which residents rely on for cooling, stormwater management, and other benefits. 

With DPCD’s support, ArMI has also advanced efforts to remove invasive plant species such as black swallow-wort, a pernicious vine native to Europe in the milkweed family. This plant outcompetes the native milkweed, and lures monarch butterflies to lay eggs on its leaves. However, this plant is poisonous and fatal to monarch caterpillars.  

Arlington’s invasive management efforts include a survey of invasives on public lands, the Pink Plants campaign and the award-winning Sustainable Landscape Handbook. In 2023, Arlington completed a survey of invasive species on over 40 public lands. Nearly all had invasives on site, which were documented in detail for management. The Pink Plants project highlights invasive species in the landscape using eco-friendly pink paint, with the aim to educate about their presence and impact. The Handbook contains tips and information to help residents take steps to make residents’ lawns more environmentally friendly. Included in the book are ways to plant native species to support both Monarch populations and biodiversity as a whole.   

The Mayors' Monarch Pledge advances these Town and volunteer-led efforts. Community members can support the Pledge to remove black swallow-wort.