Can you help me understand hardiness zones?


I’m out in Bethel, and I’m looking at buying some trees, both fruit, and landscaping. I’m trying to understand some things about hardiness zones. We’re in zone 4 (I think), though we’re not far from Zone 5, but when I look at record low temperatures in Bethel, they’re well above -20F (which is minimum for zone 5, not 4); record lows are -6F, and I’m very near to the airport, which is where I think the temperature for Bethel is recorded. I’m trying to understand if these trees are likely to be okay, or if we’re talking about a fifty-year record, or if it’s because there are mountains in town that mean we’re being placed for the max elevations, rather than the valley (where I live).

Any info would be lovely. There’s a ton that seems happy in Zone 5, but when you get to Zone 4, a lot becomes a non-option.


Pamela Hargest, Horticulture Professional

Excellent question! According to the USDA Hardiness Zone Map, it looks like Bethel is zone 4b (-25 to -20). There is always a risk with planting trees that are listed for outside your zone, but as you mentioned, you probably live in what we call a microclimate being located in the valley. Therefore, you could probably get away with planting trees intended for zone 5. I would just be cautious and pay close attention to the weather. I’ve known gardeners and farmers alike who live in microclimates (that is warmer than their designated zone) and have lost trees due to the winter or early Spring temperatures dipping below what their trees could tolerate. While the weather is warming due to climate change, it is also fluctuating even more, making conditions unpredictable at times. You may be interested in checking out the Tools and Resources available on our Maine Climate and Ag Network webpage.