Roses are red. Violets are blue. Magnolias in Manhattan? Yes, and myrtles too.
With the release of its new plant zone map, the U.S. Department of Agriculture has moved Manhattan from hardiness zone 5b to zone 6a, making it possible to grow plants seen in more southern climates here. The northern portion of Pottawatomie County still sits in zone 5b.
The USDA measured temperatures from 1976-2005 for its 2012 map, the first such map since 1990.
The average annual extreme minimum temperature determines plant hardiness zones. Zones are separated into 10-degree increments, and the new map shows that winters are getting warmer in Manhattan.
The move is a joyous one for Manhattan gardeners, said Dr. Stuart L. Warren, head of Kansas State horticulture. Between tens and hundreds of new plant species are now available for Manhattan gardeners.
“The new plants are things we look at in the southern landscape, and wished we had here” Warren said.
Those new species include southern magnolias, crepe myrtles, conifers and azaleas, Warren said.
Warren said the additional plants will bring more color to Kansas during the winter time.
“It breaks up the winter landscape nicely,” he said.
Warren and other plant experts in the area, however, are skeptical of the new designation because of Kansas’ inconsistent climate.
“It only takes one winter out of every five,” Warren said. “If it goes really low again then they (the plants) may not be killed, but they are going to look a whole lot rougher.”
Ward Upham, state extension master gardener coordinator, said “I’m not a weather expert, but we are going to continue to see a lot variety in Kansas weather. This just gives us more confidence that plants with cold hardiness will marginally survive.”
Upham said Oklahoma had a recent winter, where temperatures dipped to 30-below, which is unseen in that area.
State climatologist Mary Knapp said gardeners should be aware of the possibility that Manhattan will still likely see extreme cold temperatures, but Knapp also said that on average, it is not getting as cold as it has in the past in Manhattan.
The potential is there for Manhattan to move into zone 6b by the time the next maps are released, Knapp said, which would put the city in same hardiness zone as Wichita..