Weeks ahead of schedule, hostas and irises are pushing up through the ground. Tulips have come and gone in parts of Center City. Forsythia and magnolia trees are bursting with buds; hellebores and azaleas are opening. Snowdrops popped up in December, and winter aconite, which usually arrives in late February, arrived in early January.
"I've never, never, had a winter like this," said Kathryn Andersen, who was shocked early in the new year when her special Narcissus bulbocodium, or "hoop petticoat" daffodils, emerged in a raised bed.
"I can't believe it. They're supposed to bloom in late February or early March," said Andersen, who's planted more than 20 rows of daffodils, each 90 feet long, around her 40-acre farm.
Warm stretches in winter are not unusual. And one or two warm winters do not climate change make. But on Wednesday, as though on cue in the midst of such a winter, the U.S. Department of Agriculture released an updated color-coded map of its 1990 plant hardiness zones that shows a subtle warming - about five degrees - of much of the country the farther north you go.
Hardiness zones are based on regions' average low temperature in winter. Printed on plant tags and seed packets, they tell the nation's 80 million gardening households which plants will grow best where and when to plant vegetables without fear of frost. The information is also used by farmers, plant breeders and growers, entomologists, researchers, and others.
There are 13 zones covering all 50 states and Puerto Rico. The higher the zone number, the warmer the region, with each zone representing a 10-degree difference. The zones are further broken down into half-zones A and B, A being five degrees cooler than B.
