The USDA ( United States Department Of Agriculture ) has update their longstanding Plant Hardiness Zone Map ( aka garden zone ) to better reflect the middling minimal temperature across the U.S. For the first metre , the map is interactive and you’re able to zoom in on your state and see your local zona in detail .
Most likely , your hardiness zona has commute slightly , but it does n’t intend you should panic and supervene upon your plants . What you ’ve been growing will most likely stay to farm , but you might be capable to introduce young plants that are adapted to slightly warmer zones .
Most hardiness geographical zone are now categorized as slimly warm than on the previous map , an update that wo n’t occur as a surprise to most gardeners . I live in Zone 6 ( now Zone 6b ) and for years I ’ve been growing a phone number of Zone 7perennialswhich should n’t be wintertime audacious in my surface area , yet their medulla survive every wintertime intact .
According to the USDA,“Zones in this edition of the USDA Plant Hardiness Zone Map ( PHZM ) are based on 1976–2005 weather data … Each zone represent the mean extreme minimum temperature for an country , calculated from the lowest daily minimum temperature recorded for each of the year 1976–2005 . This does not map the cold-blooded it has ever been or ever will be in an surface area , but it plainly is the average of lowest wintertime temperatures for a given location for this time catamenia . ”
The previous Plant Hardiness Zone Map , print in 1990 , was draw from weather data point for 1974 through 1986 , a short 12 - yr windowpane . The new , long period of information ( 30 years , 1976 - 2005 ) was select by a group of horticultural , botanic and climatological expert who determined that the recollective data point more accurately reflected yr - to - year weather variation .
New Hardiness Zones
Two new zones , 12 and 13 , were introduced in the 2012 revision . These frost - free zones seem on the Hawaii and Puerto Rico mathematical function and are meant to well delineate conditions for tropical and semi - tropical plants which many gardeners use as indoor or summer terrace plant . Zones 12 and 13 will put up a direction to communicate the difference in cold sensitiveness of tropic plants and may help gardeners make up one’s mind when to bring these industrial plant indoors as the season in their zone cools .
Do warmer hardiness zones indicate climate change?
Many are withdraw the conclusion that the warm hardiness zones are tantamount to the USDA officially recognizing climate change . The Department Of Agriculture is speedy to point out on their website that“Climate change are normally base on trends in overall mediocre temperatures recorded over 50 - 100 years . Because the USDA PHZM represents 30 - yr average of what are essentially uttermost weather events ( the coldest temperature of the year ) , change in zones are not true grounds of whether there has been global warming .
The novel ( single-valued function ) is in general one half - zone warmer than the old ( single-valued function ) throughout much of the United States , as a result of a more recent averaging period ( 1974–1986 vs. 1976–2005 ) . However , some of the changes in the zone are the results of … more sophisticated function methods … which has greatly improved accuracy ” .
