Cold hardiness comes in two forms, a shorter time to maturity and actual resistance to freezing. Earlier maturation is what allows us to grow sweet potatoes in the north. Hybrid tea roses succumb to refreezing after winter thaws, but some tougher new varieties withstand this abuse much better.
The following are but a few of the new varieties of vegetables and flowers suitable for northern climes. I will discuss fruits in a subsequent article. The number in parenthesis refers to the Source List at the end of the article. The number in brackets is the hardiness zone.
Since I've mentioned them twice already I'll begin with sweet potatoes. Three new varieties that have been around for a few years are "Georgia Jet" (1), "Vardaman" (1,4) and "Centennial (1,4). All three mature in about 90 days. It is recommended that you plant them under black plastic after the last frost date in wide rows, spacing the plants every 15" in a diamond pattern. Harvest them right after the first frost.
Artichokes can be grown in the north if you start them indoors. Two varieties, "Imperial Star" (2,3,4) and "Green Globe Improved" (5) are hardy to New England. The latter can purportedly be wintered over if mulched. "Imperial Star" should be treated as an annual, and more importantly needs to be set out so that it receives at least 10 days of temps below 50 F. Since our spring temperatures fluctuate so, I'd give them at least a couple of weeks. Artichokes require cold to set the "chokes" which are actually flower buds.
I've found that one of the most difficult things to achieve in my northern New England garden is a red pepper. The successes I've had have been with varieties that mature in less than 70 days. One new introduction for 1999 is "Super Greygo II" (4) that matures in 65 days. This large sweet pepper looks more like an heirloom tomato than a pepper. A new pepperoncini type, "Robustini" (1,2,5) is an extra early 62-day variety.
