I bring this up because I recently read that the Arbor Day Foundation has re-scaled the USDA Hardiness Zone Maps, and that southern New Hampshire, like most of the US, has gone up a zone of hardiness, in our case from USDA Zone 5 (minimum -20 degrees F.) to USDA Zone 6 (minimum -10 degrees F.) These maps are generated by the USDA, and are supposed to be updated every 15 years. The last one was done in 1990, so we should be due for another one in 2005. (Wait a minute, isn't this 2007? Well, I'm sure those folks at the USDA have better things to do, such as helping "dole" out advice for the banana orchards and pineapple plantations that are sure to be springing up across the country.) The Arbor Day Foundation took the same data that the USDA uses, and produced this new map:
Is the climate truly changing? Who knows. Evidence seems to be leaning that way, especially given the recent U.N. report on the subject. It's true that this has been an unusually mild winter in
It's interesting, though, to listen to shoppers who come into The Mixed Border and ask for plants that are hardy to at least USDA Zone 4 (minimum -30 degrees F), and who live mere miles away. They cite previous problems with plants not surviving our winters, and suggest they live in a particularly cold spot. In truth, the reason their plants may not survive the winter may have less to do with how cold it gets, but how warm it was before it turned cold. In other words, having a prolonged warm fall, with nighttime temperatures that remain above freezing through November and into December, can be injurious, and sometimes fatal, to plants that are otherwise hardy. Dormancy is delayed as these plants are often the victims of a cruel deception, carried out by a capricious climate that pays the calendar no heed. For no matter how mild the fall and early winter, the icy hammer will surely be swept down from the north, carried in a frozen, unforgiving grip. Just a bit later than normal, and a hardiness zone milder.
And here we are, in early April, less than a week after the most recent storm that laid down a half a foot of slushy crisco snow over the unsuspecting snowdrops and crocuses, not to mention the pots of plants that we just uncovered from their protective winter blankets. We have had more snow in March and April than we had from November through February, and more is forecast for Thursday. With Opening Day at the nursery just 2 weeks away and counting, we are behind in our preparations, but are as eager as every other gardener to see something green.