The USDA recently updated it’s hardiness zone map with data from the last few years, and northern Maine is getting warmer. On the older maps, Masardis was zone 3B. On the updated map, we’re zone 4A. It’s an indicator of changing times. It also opens us up to a wider variety of perennials we can successfully grow.
Here’s the link: https://planthardiness.ars.usda.gov/