Maine's shifting climate: USDA updates plant hardiness zones, revealing warmer trends and new threats - WGME

Maine's shifting climate: USDA updates plant hardiness zones, revealing warmer trends and new threats | WGME

PORTLAND (WGME) -- The United States Department of Agriculture released its new and updated Plant Hardiness Zone for Maine.

This is a great tool for gardeners and growers during the growing season.

There are seven separate zones in Maine. For the first time, Portland has been recognized as a Zone 6a. These designated zones are also known as the average annual extreme minimum temperature, according to the USDA. This corresponds with the coldest night of the year.

What does this mean?

This means that plants that need Zone 6a to grow, now can. This also means that harmful or invasive plants can make their way into different territories. With the arrival of new plants, new insects have also arrived. In the past, these invasive insects could not survive the harsh New England winters, but they can now, especially in coastal Maine.

One plant species that is already making its way into New England is kudzu. Kudzu is an invasive vine that can take over plants. This plant is expected to make a full expansion into Maine in the future. On the insect side, the Brown Marmorated Stink Bug has been detected in Maine, crawling its way into New England.

The previous plant hardiness map did not include the Portland metro. Since Maine's growing season has lengthened with the first frost becoming later and later, temperatures have warmed between 0 to 5 degrees. Portland was previously in Zone 5b, with an average annual extreme minimum temperature between -15 to -10 degrees Fahrenheit. Now, Portland resides in Zone 6a, with an average annual extreme minimum temperature of between -10 and -5 degrees Fahrenheit.

You can click here for a full interactive map of the zones within the United States.