Wichita has warmed up half a zone, from 6a to 6b, under a new plant hardiness map released today by the U.S. Department of Agriculture.
The hardiness zone map, which helps gardeners determine which plants will survive the winters where they live, was last updated in 1990. Under that map, Wichita’s winters averaged lows of 10 below to 5 below zero. The new map is based on average lows from 1976 to 2005, which were 5 below zero to zero in Wichita.
The new map is much more sophisticated than the old one because of advances in technology and can’t be exactly compared to the old map, said Kim Kaplan of the Agriculture Research Service in Washington. It shows that some areas of the country have become warmer and others have become cooler since the issuance of the last map but takes into account only low temperatures and makes no claim for or against climate change, Kaplan said.
Kaplan said the map was issued because nurseries and other companies that do business in plants requested it. Home Depot, for example, wanted to know when it was best to ship, say, pansies to its stores around the country, Kaplan said.
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The maps are only a guide and don’t reflect how cold a winter can get. Wichitans have only to remember the 17 below zero last February. Even if an area’s zone changed, it doesn’t change the fact that the plants that did well in a gardener’s yard yesterday will still be doing well today, Kaplan said.
The new map is interactive and can be found on the website planthardiness.ars.usda.gov.