USDA Maps Out New Plant Hardiness Zones

New USDA Cold Hardiness Zone map

The USDA has released the new version of its Plant Hardiness Zone Map (PHZM), updating a useful tool for gardeners and researchers for the first time since 1990 with greater accuracy and detail. The new map—jointly developed by USDA’s Agricultural Research Service (ARS) and Oregon State University’s (OSU) PRISM Climate Group—is available online at www.planthardiness.ars.usda.gov

For the first time, the new map offers a Geographic Information System (GIS)-based interactive format and is specifically designed to be Internet-friendly. The map website also incorporates a “find your zone by ZIP code” function. Static images of national, regional and state maps also have been included to ensure the map is readily accessible to those who lack broadband Internet access.

“This is the most sophisticated Plant Hardiness Zone Map yet for the United States,” said Catherine Woteki, USDA Under Secretary for Research, Education and Economics. “The increases in accuracy and detail that this map represents will be extremely useful for gardeners and researchers.”

Plant hardiness zone designations represent the average annual extreme minimum temperatures at a given location during a particular time period. They do not reflect the coldest it has ever been or ever will be at a specific location, but simply the average lowest winter temperature for the location over a specified time. Low temperature during the winter is a crucial factor in the survival of plants at specific locations.

The new version of the map includes 13 zones, with the addition for the first time of zones 12 (50°F to 60°F) and 13 (60°F to 70°F). Each zone is a 10°F band, further divided into 5°F Fahrenheit zones “A” and “B.”

To help develop the new map, USDA and OSU requested that horticultural and climatic experts review the zones in their geographic area, and trial versions of the new map were revised based on their expert input.

Compared to the 1990 version, zone boundaries in this edition of the map have shifted in many areas. The new map is generally one 5°F half-zone warmer than the previous map throughout much of the United States. This is mostly a result of using temperature data from a longer and more recent time period; the new map uses data measured at weather stations during the 30-year period 1976-2005. In contrast, the 1990 map was based on temperature data from only a 13-year period of 1974-1986.

However, some of the changes in the zones are a result of new, more sophisticated methods for mapping zones between weather stations. These include algorithms that considered for the first time such factors as changes in elevation, nearness to large bodies of water, and position on the terrain, such as valley bottoms and ridge tops. Also, the new map used temperature data from many more stations than did the 1990 map. These advances greatly improved the accuracy and detail of the map, especially in mountainous regions of the western U.S. In some cases, they resulted in changes to cooler, rather than warmer, zones.

While about 80 million American gardeners, as well as those who grow and breed plants, are the largest users of the USDA Plant Hardiness Zone Map, many others need this hardiness zone information. For example, the USDA Risk Management Agency uses the USDA plant hardiness zone designations to set some crop insurance standards. Scientists use the plant hardiness zones as a data layer in many research models such as modeling the spread of exotic weeds and insects.

Although a poster-sized version of this map will not be available for purchase from the government as in the past, anyone may download the map free of charge from the Internet onto their personal computer and print copies of the map as needed.

Leave a Reply

Featured Stories

VegetablesFormer Harris Seeds Co. CEO, Per Jensen, Passes At 85
November 21, 2014
A passion for plants defined longtime industry influencer. Read More
GrapesPerfect Storm Hurts New York Concord Grape Growers
November 21, 2014
More than 10,000 tons of juice grapes are abandoned because of too much production and no market. Read More
FruitsClassic Turkey Day Dinner Costing Consumers More This Year
November 20, 2014
Despite increase, a family of 10 can still get stuffed for less than $50. Read More
Insect ControlFlorida Vegetable Growers Gain Access To New Nematicide
November 20, 2014
Methyl bromide alternative Nimitz approved for use on tomatoes, peppers, okra, eggplant, cucumber, watermelon, cantaloupe, and squash. Read More
EquipmentHighlights From EIMA International In Italy [Slideshow]
November 19, 2014
The 2014 edition of the International Agricultural and Gardening Machinery Exhibition (EIMA) boasted a record number of attendees from 124 countries. Read More
Farm ManagementVegetableGrowerConnect Delivers Results For Growers And Suppliers [slideshow]
November 19, 2014
Suppliers and growers got down to business in San Diego discussing current needs, solutions, and ways to increase efficiencies on the farm. Browse this slideshow for VegetableGrowerConnect highlights. Read More
FruitsFixing Farm Labor Woes Worth The Extra Effort [Opinion]
November 19, 2014
40th annual Ag Labor Relations Forum encourages outreach and action. Read More
BerriesPackaging Company’s Campaign To Benefit Future Organic Farmers
November 19, 2014
Sambrailo Packaging of Watsonville, CA, has partnered with California Certified Organic Farmers and will donate a portion of the sales of clamshells made from plastic bottles. Read More
Apples & PearsOn The Road With The International Fruit Tree Association Study Tour To Italy Part 1 [Slideshow]
November 19, 2014
Win Cowgill of Rutgers University details a trip through the one of the most concentrated fruit growing areas in the world, the South Tyrol region of Italy. Read More
IrrigationAlmond Grower Honored For Water Efficiency
November 18, 2014
Ongoing drought highlights the efforts of third-generation Madera County grower Tom Rogers. Read More

The Latest

VegetablesFormer Harris Seeds Co. CEO, Per Jensen, Passes At 85
November 21, 2014
A passion for plants defined longtime industry influencer. Read More
GrapesPerfect Storm Hurts New York Concord Grape Growers
November 21, 2014
More than 10,000 tons of juice grapes are abandoned because of too much production and no market. Read More
FruitsClassic Turkey Day Dinner Costing Consumers More This Y…
November 20, 2014
Despite increase, a family of 10 can still get stuffed for less than $50. Read More
Insect ControlFlorida Vegetable Growers Gain Access To New Nematicide
November 20, 2014
Methyl bromide alternative Nimitz approved for use on tomatoes, peppers, okra, eggplant, cucumber, watermelon, cantaloupe, and squash. Read More
EquipmentHighlights From EIMA International In Italy [Slideshow]
November 19, 2014
The 2014 edition of the International Agricultural and Gardening Machinery Exhibition (EIMA) boasted a record number of attendees from 124 countries. Read More
Farm ManagementVegetableGrowerConnect Delivers Results For Growers And…
November 19, 2014
Suppliers and growers got down to business in San Diego discussing current needs, solutions, and ways to increase efficiencies on the farm. Browse this slideshow for VegetableGrowerConnect highlights. Read More
FruitsFixing Farm Labor Woes Worth The Extra Effort [Opinion]
November 19, 2014
40th annual Ag Labor Relations Forum encourages outreach and action. Read More
BerriesPackaging Company’s Campaign To Benefit Future Organi…
November 19, 2014
Sambrailo Packaging of Watsonville, CA, has partnered with California Certified Organic Farmers and will donate a portion of the sales of clamshells made from plastic bottles. Read More
Apples & PearsOn The Road With The International Fruit Tree Associati…
November 19, 2014
Win Cowgill of Rutgers University details a trip through the one of the most concentrated fruit growing areas in the world, the South Tyrol region of Italy. Read More
IrrigationAlmond Grower Honored For Water Efficiency
November 18, 2014
Ongoing drought highlights the efforts of third-generation Madera County grower Tom Rogers. Read More
CitrusWomen’s Impact On Agriculture Impressive [Opinion…
November 18, 2014
Florida Agriculture Commissioner Adam Putnam says the long-term sustainability of farming depends on our youth. Read More
Apples & PearsFall Sprays For BMSB Can Cause San Jose Scale Flare Up
November 18, 2014
Penn State University research entomologist says prevention is best control option for devastating pest. Read More
CitrusPrograms Burgeon To Promote Citrus Plantings
November 17, 2014
Processors and USDA step up to support growers who are putting new trees in the ground. Read More
Business PlanningFarm Executive Workshop To Build Management, Leadership…
November 17, 2014
Penn State Extension offering unique learning event for those looking to bolster business. Read More
BerriesGeorgia Is The Top Blueberry State In The Nation
November 17, 2014
The Peach State experiences extreme growth in production of blueberries in the last 20 years. Read More
GrapesSenator Launches Campaign To Open Foreign Markets To Mo…
November 17, 2014
If tariff is reduced, exporters could buy more; would help alleviate surplus grape supply. Read More
Apples & PearsPromising Technology To Expand Hard Cider Industry
November 14, 2014
Demand growing as researchers explore the possibilities of mechanical harvesting. Read More
Grapefruit & SpecialtyFlorida Grapefruit Growers Feeling Good About Early Cro…
November 14, 2014
Producers, packers, and suppliers view initial USDA outlooks as positive predictor for future. Read More