Hey everyone! I've been thinking about how USDA plant hardiness zones are determined mainly by the lowest temperatures in those areas. With climate change shaking things up, shouldn't we also think about adding an upper limit to these zones? Extreme heat can be just as harmful to plants as extreme cold, right? For example, I live in Zone 9b on the Oregon coast where temperatures rarely drop below 25-30°F, and we usually don't go above 75°F. Meanwhile, Paso Robles, CA is also Zone 9b, but their temperatures can soar to daily highs around 97°F in the summer, even reaching up to 115°F in recent years. I wouldn't dream of planting some of the things I have in Oregon if I lived in Paso Robles! So, considering the rising temperatures everywhere, do you think we should redefine hardiness zones to also factor in extreme highs?
1 Answer
That's an interesting thought! I'm not sure how they'd manage redefining the zones though. I'm in a 6B area, and it feels complicated with temperature extremes. We go from 0°F to 104°F throughout the year, making it tough to plant cool-weather crops in spring; I usually wait until fall! Plus, the temperature swings can be wild, like going from 80°F in April to 60°F in May. I'm definitely noticing the change in climate though—I'm watering my plants every day now!
Totally feel you on that! I'm in 6B too, and I've had the same experience. We went from freezing temps to summer heat in no time, which really struggled my spring flowers. Only my pansies, which survived the winter, did well early on. Everything else, like ranunculus, just couldn't handle the heat.