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A hardiness zone is a geographic area defined as having a certain range of annual minimum temperature, a factor relevant to the survival of many plants. In some systems other statistics are included in the calculations. The original and most widely used system, developed by the
United States Department of Agriculture The United States Department of Agriculture (USDA), also known as the Agriculture Department, is the federal executive department responsible for developing and executing federal laws related to farming, forestry, rural economic development, ...
(USDA) as a rough guide for landscaping and gardening, defines 13 zones by long-term average annual extreme minimum temperatures. It has been adapted by and to other countries (such as Canada) in various forms. Unless otherwise specified, in American contexts "hardiness zone" or simply "zone" usually refers to the USDA scale. For example, a plant may be described as "hardy to zone 10": this means that the plant can withstand a minimum temperature of 30 °F (−1.1 °C) to 40 °F (4.4 °C). Other hardiness rating schemes have been developed as well, such as the UK
Royal Horticultural Society The Royal Horticultural Society (RHS), founded in 1804 as the Horticultural Society of London, is the UK's leading gardening Gardening is the practice of growing and cultivating plants as part of horticulture Horticulture is the art of cultiva ...
and US Sunset Western Garden Book systems. A heat zone (see below) is instead defined by annual high temperatures; the
American Horticultural Society The American Horticultural Society (AHS) is a nonprofit, membership-based organization that promotes excellence in American horticulture Horticulture is the art of cultivating plants in gardens to produce food and medicinal ingredients, or for comf ...
(AHS) heat zones use the average number of days per year when the temperature exceeds .


United States hardiness zones (USDA scale)

The USDA system was originally developed to aid gardeners and landscapers in the United States. State-by-state maps, along with an electronic system that allows finding the zone for a particular zip code, can be found at th
USDA Agricultural Research Service (USDA-ARS) website.
In the United States, most of the warmer zones (zones 9, 10, and 11) are located in the deep southern half of the country and on the southern coastal margins. Higher zones can be found in
Hawaii Hawaii ( ; haw, Hawaii or ) is a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State (newspaper), ''The State'' (newspape ...

Hawaii
(up to 12) and
Puerto Rico Puerto Rico (; abbreviated PR; tnq, Boriken, ''Borinquen''), officially the Commonwealth of Puerto Rico ( es, link=yes, Estado Libre Asociado de Puerto Rico, lit=Free Associated State of Puerto Rico) is a Caribbean island and Unincorporated ...

Puerto Rico
(up to 13). The southern middle portion of the mainland and central coastal areas are in the middle zones (zones 8, 7, and 6). The far northern portion on the central interior of the mainland have some of the coldest zones (zones 5, 4, and small area of zone 3) and often have much less consistent range of temperatures in winter due to being more continental, and thus the zone map has its limitations in these areas. Lower zones can be found in
Alaska Alaska (; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Central Alaskan Yup'ik language, Yup'ik: ''Alaskaq''; tli, Anáaski) is a U.S. state in the Western United States, on the northwest extremity of the country's West Coast of the United State ...

Alaska
(down to 1). The low latitude and often stable weather in
Florida Florida is a U.S. state, state located in the Southeastern United States, Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia (U.S. state), Geor ...

Florida
, the
Gulf Coast The Gulf Coast of the United States is the coastline The coast, also known as the coastline or seashore, is defined as the area where land meets the sea or ocean, or as a line that forms the boundary between the land and the ocean T ...

Gulf Coast
, and southern
Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak) is a state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State (newspaper), ...

Arizona
and
California California is a U.S. state, state in the Western United States. With over 39.3million residents across a total area of approximately , it is the List of states and territories of the United States by population, most populous and the List of ...

California
, are responsible for the rarity of episodes of severe cold relative to normal in those areas. The warmest zone in the 48 contiguous states is the
Florida Keys The Florida Keys are a coral island, coral cay archipelago located off the southern coast of Florida, forming the southernmost part of the continental United States. They begin at the southeastern coast of the Florida peninsula, about south of ...
(11b) and the coldest is in north-central
Minnesota Minnesota () is a U.S. state, state in the Upper Midwest, upper Midwestern United States. It is the List of U.S. states and territories by area, 12th largest U.S. state in area and the List of U.S. states and territories by population, 22nd m ...

Minnesota
(3a).
Puerto Rico Puerto Rico (; abbreviated PR; tnq, Boriken, ''Borinquen''), officially the Commonwealth of Puerto Rico ( es, link=yes, Estado Libre Asociado de Puerto Rico, lit=Free Associated State of Puerto Rico) is a Caribbean island and Unincorporated ...

Puerto Rico
has the warmest hardiness zone in the United States at 13a. Conversely,
Fort Yukon, Alaska Fort Yukon (''Gwichyaa Zheh'' in Gwich'in) is a city in the Yukon-Koyukuk Census Area in the U.S. state In the United States The United States of America (USA), commonly known as the United States (U.S. or US), or America, is a coun ...
has the coldest hardiness zone for any city in the United States at 1a.


Definitions


History

The first attempts to create a geographical hardiness zone system were undertaken by two researchers at the
Arnold Arboretum The Arnold Arboretum of Harvard University Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts. Established in 1636 and named for its first benefactor, clergyman John Harvard (cler ...
in
Boston Boston (, ), officially the City of Boston, is the capital city, capital and List of municipalities in Massachusetts, most populous city of the Commonwealth (U.S. state), Commonwealth of Massachusetts in the United States and 21st List of Unit ...

Boston
: the first was published in 1927 by
Alfred Rehder Alfred Rehder (4 September 1863 in Waldenburg, Saxony – 25 July 1949 in Jamaica Plain, Massachusetts Jamaica Plain is a neighborhood of in the City of Boston, Massachusetts, United States The United States of America (USA), com ...

Alfred Rehder
, and the second by
Donald WymanDonald Wyman (1904 — 6 December 1993) was an American horticulturist, the head of horticulture at Harvard University Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts. Established ...
in 1938. The Arnold map was subsequently updated in 1951, 1967, and finally 1971, but eventually fell out of use completely. The modern USDA system began at the US National Arboretum in
Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** Federal government of the United States (metonym) ** Washington metropolitan area, the metropolitan area centered on Washingt ...
. The first map was issued in 1960, and revised in 1965. It used uniform 10-degree Fahrenheit ranges, and gradually became widespread among American gardeners. The USDA map was revised and reissued in 1990 with freshly available climate data, this time with 5-degree distinctions dividing each zone into new "a" and "b" subdivisions. In 2003, the
American Horticultural Society The American Horticultural Society (AHS) is a nonprofit, membership-based organization that promotes excellence in American horticulture Horticulture is the art of cultivating plants in gardens to produce food and medicinal ingredients, or for comf ...
(AHS) produced a draft revised map, using temperature data collected from July 1986 to March 2002. The 2003 map placed many areas approximately a half-zone higher (warmer) than the USDA's 1990 map. Reviewers noted the map zones appeared to be closer to the original USDA 1960 map in its overall zone delineations. Their map purported to show finer detail, for example, reflecting
urban heat island Image:Urban heat island.svg, 300px, Mechanism of the urban heat island effect An urban heat island (UHI) is an urban area or metropolitan area that is significantly warmer than its surrounding rural areas due to human activities. The temperat ...

urban heat island
s by showing the downtown areas of several cities (e.g.,
Baltimore, Maryland Baltimore ( , locally: ) is the most populous city The United Nations uses three definitions for what constitutes a city, as not all cities in all jurisdictions are classified using the same criteria. Cities may be defined as the city prop ...
;
Washington, D.C. ) , image_skyline = , image_caption = Clockwise from top left: the Washington Monument The Washington Monument is an obelisk within the National Mall The National Mall is a Landscape architecture, landscaped ...
and
Atlantic City, New Jersey Atlantic City, often known by its initials A.C., is a coastal Resort town, resort city in Atlantic County, New Jersey, Atlantic County, New Jersey, United States, known for its casinos, Boardwalk (entertainment district), boardwalk, and beache ...
) as a full zone warmer than outlying areas. The map excluded the detailed a/b half-zones introduced in the USDA's 1990 map, an omission widely criticized by horticulturists and gardeners due to the coarseness of the resulting map. The USDA rejected the AHS 2003 draft map and created its own map in an interactive computer format, which the
American Horticultural Society The American Horticultural Society (AHS) is a nonprofit, membership-based organization that promotes excellence in American horticulture Horticulture is the art of cultivating plants in gardens to produce food and medicinal ingredients, or for comf ...
now uses. In 2006, the
Arbor Day Foundation The Arbor Day Foundation is a 501(c)(3) nonprofit conservation and education organization founded in 1972 in Nebraska Nebraska is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It is bordered b ...
released an update of U.S. hardiness zones, using mostly the same data as the AHS. It revised hardiness zones, reflecting generally warmer recent temperatures in many parts of the country, and appeared similar to the AHS 2003 draft. The Foundation also did away with the more detailed a/b half-zone delineations. In 2012 the USDA updated their plant hardiness map based on 1976–2005 weather data, using a longer period of data to smooth out year-to-year weather fluctuations. Two new zones (12 and 13) were added to better define and improve information sharing on tropical and semitropical plants, they also appear on the maps of Hawaii and Puerto Rico. There is a very small spot east of
San JuanSan Juan , Spanish for Saint John (disambiguation), Saint John, may refer to: Places Argentina * San Juan Province, Argentina * San Juan, Argentina, the capital of that province * San Juan (Iruya), a small village in the Iruya Department of the ...
, Puerto Rico that includes the airport in coastal Carolina, where the mean minimum is 67 degrees F (19 C), which is classified as hardiness Zone 13b, the highest category, with temperatures rarely below . The map has a higher resolution than previous ones, and is able to show local variations due to things such as elevation or large bodies of water. Many zone boundaries were changed as a result of the more recent data, as well as new mapping methods and additional information gathered. Many areas were a half zone warmer than the previous 1990 map. The 2012 map was created digitally for the internet, and includes a
ZIP Code#REDIRECT ZIP Code A ZIP Code is a postal code used by the United States Postal Service (USPS). Introduced in 1963, the basic format consisted of five digits. In 1983, an extended ZIP+4 code was introduced; it included the five digits of the ZIP ...
zone finder and an interactive map. In 2015, the Arbor Day Foundation revised another map, also with no a and b subdivisions, showing many areas having zones even warmer, with the most notable changes in the Mid Atlantic and Northeast, showing cities like Philadelphia, New York City and Washington D.C in zone 8, due to their urban heat islands.


Selected U.S. cities

The USDA plant hardiness zones for selected U.S. cities as based on the 2012 map are the following:


Limitations

As the USDA system is based entirely on average annual extreme minimum temperature in an area, it is limited in its ability to describe the climatic conditions a gardener may have to account for in a particular area: there are many other factors that determine whether or not a given plant can survive in a given zone. Zone information alone is often not adequate for predicting winter survival, since factors such as frost dates and frequency of snow cover can vary widely between regions. Even the extreme minimum itself may not be useful when comparing regions in widely different climate zones. As an extreme example, due to the
Gulf stream The Gulf Stream, together with its northern extension the North Atlantic Drift The North Atlantic Current (NAC), also known as North Atlantic Drift and North Atlantic Sea Movement, is a powerful warm western boundary current Boundary curren ...
most of the United Kingdom is in zones 8–9, while in the US, zones 8–9 include regions such as the subtropical coastal areas of the
southeastern US The southeastern United States, also referred to as the American Southeast or simply the Southeast, is broadly the eastern portion of the southern United States and the southern portion of the eastern United States. It comprises at least a cor ...
and
Mojave Mojave or Mohave most often refers to: *Mojave Desert *Mojave River *Mohave people Mojave or Mohave may also refer to: Places * Fort Mojave Indian Reservation * Mohave County, Arizona * Mohave Valley, a valley in Arizona * Mohave Valley, Arizona, ...

Mojave
and
Chihuahuan
Chihuahuan
inland deserts, thus an American gardener in such an area may only have to plan for several nights of cold temperatures per year, while their British counterpart may have to plan for several months. In addition, the zones do not incorporate any information about summer temperature or
insolation Solar irradiance is the power Power typically refers to: * Power (physics) In physics, power is the amount of energy transferred or converted per unit time. In the International System of Units, the unit of power is the watt, equal to one j ...

insolation
; thus sites which may have the same mean winter minima, but markedly different summer temperatures, will be accorded the same hardiness zone. For example, zone 8 covers coastal, high latitude, cool summer locations like
Seattle Seattle ( ) is a seaport The Porticciolo del Cedas port in Barcola The thumb is the first digit of the hand, next to the index finger. When a person is standing in the medical anatomical position (where the palm is facing to the front) ...

Seattle
and
London London is the capital Capital most commonly refers to: * Capital letter Letter case (or just case) is the distinction between the letters that are in larger uppercase or capitals (or more formally ''majuscule'') and smaller lowerc ...

London
, as well as lower latitude, hot summer climates like
Charleston Charleston most commonly refers to: * Charleston, South Carolina Charleston is the largest city in the U.S. state of South Carolina, the county seat of Charleston County, South Carolina, Charleston County, and the principal city in the Charle ...

Charleston
and
Madrid Madrid ( , ) is the capital and most populous city of Spain , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = , national_anthem = , image_ ...
. Farmers, gardeners, and landscapers in the former two must plan for entirely different growing seasons from those in the latter. Coastal Ireland and central Florida are both Zone 10, but have radically different insolation and summer heat and humidity. The hardiness scales do not take into account the reliability of snow cover in the colder zones. Snow acts as an insulator against extreme cold, protecting the root system of hibernating plants. If the snow cover is reliable, the actual temperature to which the roots are exposed will not be as low as the hardiness zone number would indicate. As an example,
Quebec City Quebec City ( or ; french: Ville de Québec), officially Québec (), is the capital city of the Canadian province The provinces and territories of Canada () are sub-national divisions within the geographical areas of Canada under the juri ...

Quebec City
in Canada is located in zone 4, but can rely on a significant snow cover every year, making it possible to cultivate plants normally rated for zones 5 or 6. But, in
Montreal Montreal ( ; officially Montréal, ) is the second-most populous city in Canada Canada is a country in the northern part of . Its extend from the to the and northward into the , covering , making it the world's . Its southern and w ...

Montreal
, located to the southwest in zone 5, it is sometimes difficult to cultivate plants adapted to the zone because of the unreliable snow cover. Many plants may survive in a locality but will not flower if the day length is insufficient or if they require
vernalization Vernalization (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the R ...
(a particular duration of low temperature). There are many other climate parameters that a farmer, gardener, or landscaper may need to take into account as well, such as humidity, precipitation, storms, rainy-dry cycles or monsoons, and site considerations such as soil type, soil drainage and water retention, water table, tilt towards or away from the sun, natural or manmade protection from excessive sun, snow, frost, and wind, etc. The annual extreme minimum temperature is a useful indicator, but ultimately only one factor among many for plant growth and survival.


Alternatives

An alternative means of describing plant hardiness is to use "indicator plants". In this method, common plants with known limits to their range are used. ''
Sunset Sunset, also known as sundown, is the daily disappearance of the Sun below the horizon The horizon is the apparent line that separates earth Earth is the third planet from the Sun and the only astronomical object known to harbor ...
'' publishes a series that breaks up climate zones more finely than the USDA zones, identifying 45 distinct zones in the US, incorporating ranges of temperatures in all seasons, precipitation, wind patterns, elevation, and length and structure of the growing season.''Sunset National Garden Book''. Sunset Books Inc. Menlo Park, California (1997) In addition, the Köppen climate classification system can be used as a more general guide to growing conditions when considering large areas of the Earth's surface or attempting to make comparisons between different continents. The
Trewartha climate classification Trewartha and Andrewartha are Cornish family name In some cultures, a surname, family name, or last name is the portion of one's personal name that indicates their family, tribe or community. Practices vary by culture. The family name may ...
is often a good "real world" concept of climates and their relation to plants and their average growing conditions.


Australian hardiness zones

The USDA hardiness zones are not used in Australia. The
Australian National Botanic Gardens The Australian National Botanic Gardens (ANBG) is a heritage-listed botanical garden A botanical garden or botanic gardenThe terms ''botanic'' and ''botanical'' and ''garden'' or ''gardens'' are used more-or-less interchangeably, although th ...

Australian National Botanic Gardens
have devised another system more in keeping with Australian conditions. The zones are defined by steps of 5 degrees Celsius, from −15–−10 °C for zone 1 to 15–20 °C for zone 7. They are numerically about 6 lower than the USDA system. For example, Australian zone 3 is roughly equivalent to USDA zone 9. The higher Australian zone numbers had no US equivalents prior to the 2012 addition by USDA of zones 12 and 13. The spread of weather stations may be insufficient and too many places with different climates are lumped together. Only 738 Australian stations have records of more than ten years (one station per ), though more populated areas have relatively fewer hectares per station.
Mount Isa Mount Isa ( ) is a city in the Gulf Country region of Queensland, Australia. It came into existence because of the vast mineral deposits found in the area. Mount Isa Mines (MIM) is one of the most productive single mines in world history, based ...
has three climatic stations with more than a ten-year record. One is in zone 4a, one in zone 4b, and the other is in zone 5a. Sydney residents are split between zones 3a and 4b. Different locations in the same city are suitable for different plants.


Canadian hardiness zones

Climate variables that reflect the capacity and detriments to plant growth are used to develop an index that is mapped to Canada's Plant Hardiness Zones. This index comes from a formula originally developed by Ouellet and Sherk in the mid-1960s. The formula used is: where: * Y = estimated index of suitability * X1 = monthly mean of the daily minimum temperatures (°C) of the coldest month * X2 = mean frost free period above 0 °C in days * X3 = amount of rainfall (R) from June to November, inclusive, in terms of R/(R+a) where a=25.4 if R is in millimeters and a=1 if R is in inches * X4 = monthly mean of the daily maximum temperatures (°C) of the warmest month * X5 = winter factor expressed in terms of (0 °C – X1)Rjan where Rjan represents the rainfall in January expressed in mm * X6 = mean maximum snow depth in terms of S/(S+a) where a=25.4 if S is in millimeters and a=1 if S is in inches * X7 = maximum wind gust in (km/hr) in 30 years. For practical purposes, Canada has adopted the American hardiness zone classification system. The 1990 version of the USDA Plant Hardiness Zone Map included Canada and Mexico, but they were removed with the 2012 update to focus on the United States and Puerto Rico. The Canadian government publishes both Canadian and USDA-style zone maps.


European hardiness zones


Selected European cities

The table below provides USDA hardiness zone data for selected European cities:


Britain and Ireland

Owing to the moderating effect of the
North Atlantic Current The North Atlantic Current (NAC), also known as North Atlantic Drift and North Atlantic Sea Movement, is a powerful warm western boundary current Boundary currents are ocean current An ocean current is a continuous, directed movement of se ...
on the Irish and British
temperate In geography Geography (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its populati ...
maritime climate Maritime may refer to: Geography * Maritime Alps it, Alpi Marittime , photo=Maritime Alps.jpg , photo_caption=Maritime Alps , country_type= Countries , country= , subdivision1_type= Regions, Régions , subdivision1= , parent= Alps , bor ...
, Britain, and Ireland even more so, have milder winters than their northerly position would otherwise afford. This means that the USDA hardiness zones relevant to Britain and Ireland are quite high, from 7 to 10, as shown below. USDA zones do not work particularly well in the UK as they are designed for a continental climate. The cooler UK summers must be considered. New growth may be insufficient or fail to harden off affecting winter survival. In 2012 the United Kingdom's Royal Horticultural Society introduced new hardiness ratings for plants, not places. These run from H7, the hardiest (tolerant of temperatures below ) to H1a (needing temperatures above ). The RHS hardiness ratings are based on absolute minimum winter temperatures (in °C) rather than the long-term average annual extreme minimum temperatures that define USDA zones.


Scandinavia and Baltic Sea Region

Scandinavia lies at the same latitude as Alaska or Greenland, but the effect of the warm
North Atlantic Current The North Atlantic Current (NAC), also known as North Atlantic Drift and North Atlantic Sea Movement, is a powerful warm western boundary current Boundary currents are ocean current An ocean current is a continuous, directed movement of se ...
is even more pronounced here than it is in Britain and Ireland. Save for a very small spot near
Karasjok ( se, Kárášjohka ; fkv, Kaarasjoki) is a municipality A municipality is usually a single having status and powers of self-government or jurisdiction as granted by national and regional laws to which it is subordinate. The term ''mu ...
, Norway, which is in zone 2, nowhere in the Arctic part of Scandinavia does it get below zone 3. The
Faroe Islands The Faroe Islands ( ), or simply the Faroes or Faeroes ( fo, Føroyar ; da, Færøerne ), are a North Atlantic archipelago An archipelago ( ), sometimes called an island group or island chain, is a chain, cluster or collection of is ...

Faroe Islands
, at 62–63°N are in zone 8, as are the outer
Lofoten Islands Lofoten () is an archipelago An archipelago ( ), sometimes called an island group or island chain, is a chain, cluster or collection of islands, or sometimes a sea containing a small number of scattered islands. Indonesian Archipelago, A ...

Lofoten Islands
at 68°N.
Tromsø Tromsø (, , ; se, Romsa ; fkv, Tromssa; sv, Tromsö) is a municipality A municipality is usually a single administrative division Administrative division, administrative unitArticle 3(1). , country subdivision, administrative regio ...

Tromsø
(, a coastal city in Norway at 70°N, is in zone 7, and even
Longyearbyen Longyearbyen (; ) is the largest settlement and the administrative centre of Svalbard Svalbard ( , ), previously known as Spitsbergen, or Spitzbergen, is a Norwegian Norwegian, Norwayan, or Norsk may refer to: *Something of, from, or ...

Longyearbyen
, the northernmost true city in the world at 78°N, is still in zone 4. All these coastal locations have one thing in common, though, which are cool, damp summers, with temperatures rarely exceeding (or in Longyearbyen). This shows the importance of taking heat zones into account for better understanding of what may or may not grow. In Sweden and Finland generally, at sea level to , zone 3 is north of the Arctic Circle, including cities like
Karesuando Karesuando (; fi, Kaaresuvanto or ; Sami: , or ) is the northernmost locality in Sweden. It is situated in Kiruna Municipality, Norrbotten County Norrbotten County ( sv, Norrbottens län; se, Norrbottena leatna, fi, Norrbottenin lääni) is ...
and
Pajala Pajala is a and the seat of in , , with 1,958 inhabitants in 2010. It is the northernmost municipal seat located in Swedish . Pajala is in the and was dominated by people speaking a dialect until Eastern Sweden (Finland) got annexed by Russia ...

Pajala
.
Kiruna (; se, Giron ; fi, Kiiruna ) is the northernmost town A town is a human settlement In geography Geography (from Greek: , ''geographia'', literally "earth description") is a field of science devoted to the study of the l ...

Kiruna
is the major exception here, which being located on a hill above frost traps, is in zone 5. Zone 4 lies between the Arctic Circle and about 64–66°N, with cities such as
Oulu Oulu ( , ; sv, Uleåborg ; la, Uloa) is a city A city is a large .Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Science Encyclopedia''. 2nd edition. London ...
,
Rovaniemi Rovaniemi ( , ; sme, Roavvenjárga ; smn, Ruávinjargâ; sms, Ruäʹvnjargg) is a city A city is a large human settlement.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ...
and
Jokkmokk Jokkmokk (; smj, Jåhkåmåhkke or ; se, Dálvvadis; fi, Jokimukka) is a locality and the seat of Jokkmokk Municipality in Norrbotten County, province A province is almost always an administrative division within a country or state. The term ...

Jokkmokk
, zone 5 (south to 61–62°N) contains cities such as
Tampere Tampere ( , , ; sv, Tammerfors ; la, Tammerforsia) is a city in the Pirkanmaa Regions of Finland, region, located in the western part of Finland. Tampere is the most populous inland city in the Nordic countries; it has a population of 238,14 ...

Tampere
,
Umeå Umeå ( , , , locally ; Norrland dialects#South Westrobothnian, South Westrobothnian: ;). fi, Uumaja; sju, Ubmeje; sma, Upmeje; se, Ubmi) is a city in northeast Sweden. It is the seat of Umeå Municipality and the capital of Västerbotten Co ...

Umeå
, and
Östersund Östersund (; sma, Staare) is an Urban areas in Sweden, urban area (Stad (Sweden), city) in Jämtland in the middle of Sweden. It is the seat of Östersund Municipality and the capital of Jämtland County. Östersund is located at the shores of Sw ...

Östersund
. Zone 6 covers the south of mainland Finland, Sweden north of 60°N, and the high plateau of
Småland Småland () is a historical Provinces of Sweden, province (''landskap'') in southern Sweden. Småland borders Blekinge, Scania (Swedish: ''Skåne''), Halland, Västergötland, Östergötland and the island Öland in the Baltic Sea. The name Små ...

Småland
further south. Here one will find cities such as
Gävle Gävle () is a city A city is a large .Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Science Encyclopedia''. 2nd edition. London: Routledge. It can be defined ...
,
Örebro Örebro ( , ) is a Stad (Sweden), city with 124,027 inhabitants, the seat of Örebro Municipality and the capital of Örebro County in Sweden. It is the sixth largest city in Sweden and one of the largest inland hubs of the country. It is located ...
,
Sundsvall Sundsvall () is a Cities in Sweden, city and the seat of Sundsvall Municipality in Västernorrland County, Sweden. It has a population of 58,807 as of 2020; more than 95,000 live in the Sundsvall Municipality, municipal area. It is Sweden's 21st ...

Sundsvall
, and
Helsinki Helsinki ( or ; ; sv, Helsingfors, ; la, Helsingia) is the capital Capital most commonly refers to: * Capital letter Letter case (or just case) is the distinction between the letters that are in larger uppercase or capitals (or ...

Helsinki
.
Åland Åland (; fi, Ahvenanmaa: ; ; ) is an Federacy, autonomous and Demilitarized zone, demilitarised region of Finland since 1920 by a decision of the League of Nations. It is the smallest region of Finland, constituting 0.51% of its land area an ...
, as well as coastal southern Sweden, and the
Stockholm Stockholm (; ) is the capital Capital most commonly refers to: * Capital letter Letter case (or just case) is the distinction between the letters that are in larger uppercase or capitals (or more formally ''majuscule'') and smalle ...

Stockholm
area are in zone 7. The west coast of Sweden (
Gothenburg Gothenburg (; abbreviated Gbg; sv, Göteborg ) is the List of urban areas in Sweden by population, second-largest city in Sweden, fifth-largest in the Nordic countries, and capital city, capital of the Västra Götaland County. It is situate ...

Gothenburg
and southwards) enjoys particularly mild winters and lies in zone 7, therefore being friendly to some hardy exotic species (found, for example, in the
Gothenburg Botanical Garden The Gothenburg Botanical Garden ( sv, Göteborgs botaniska trädgård) is located in Gothenburg, Sweden, and is one of the larger botanical gardens in Europe. History The Gothenburg Botanical Garden is situated in a formerly completely rural ar ...
), the southeast coast of Sweden has a colder winter due to the absence of the Gulf Stream. Denmark is in zones 9a, 8b, and 8a. Estonia is divided to warmer West and North coast (Tallinn 6b, Haapsalu 7b, Kärdla 7a, Kuressaare 7a, Paide 6a, Rakvere 6a, Narva 6a, Viljandi 6b) and colder inland (Tartu 5a, Valga 5a, Võru 5a). Latvia's capital Riga is in zone 6b. The country is in zones 5a, 5b, 6a, 6b, 7a and 7b. Lithuania is in zones 5a, 5b, 6a, 6b, 7a and 7b.


Central Europe

Central Europe is a good example of a transition from an
oceanic climate An oceanic climate, also known as a maritime climate or marine climate, is the Köppen classification of climate Climate is the long-term pattern of weather Weather is the state of the atmosphere, describing for example the deg ...
to a
continental climate Continental climates often have a significant annual variation in temperature (hot summers and cold winters). They tend to occur in the middle latitudes (40 to 55 north), within large landmasses where prevailing winds blow overland, and temperat ...
, which reflects in the tendency of the hardiness zones to decrease mainly eastwards instead of northwards. Also, the plateaus and low mountain ranges in this region have a significant impact on how cold it might get during winter. Generally speaking, the hardiness zones are high considering the latitude of the region, although not as high as Northern Europe with the
Shetland Islands Shetland ( on, Hjaltland; sco, Shetland; nrn, Hjetland), also called the Shetland Islands and formerly Zetland, is a subarctic archipelago in the Northern Atlantic, between Great Britain, the Faroe Islands and Norway. It is the northernmos ...
where zone 9 extends to over 60°N. In Central Europe, the relevant zones decrease from zone 8 on the Belgian, Dutch, and German
North Sea The North Sea is a sea The sea, connected as the world ocean or simply the ocean The ocean (also the sea or the world ocean) is the body of salt water which covers approximately 71% of the surface of the Earth.
coast, with the exception of some of the
Frisian Islands The Frisian Islands, also known as the Wadden Islands or the Wadden Sea Islands, form an archipelago An archipelago ( ), sometimes called an island group or island chain, is a chain, cluster or collection of islands, or sometimes a sea conta ...
(notably
Vlieland Vlieland (; fry, Flylân) is a municipality A municipality is usually a single administrative division Administrative division, administrative unitArticle 3(1). , country subdivision, administrative region, subnational entity, first- ...
and
Terschelling Terschelling (; fry, Skylge; Terschelling dialect: ''Schylge'') is a municipality A municipality is usually a single administrative division having Municipal corporation, corporate status and powers of self-government or jurisdiction as ...

Terschelling
), the island of
Helgoland Heligoland (; german: link=no, Helgoland ; Heligolandic dialect, Heligolandic Frisian: ''deät Lun'', , Mooring (North Frisian dialect), Mooring Frisian: ''Hålilönj,'' Danish: ''Helgoland'') is a small archipelago in the North Sea. A part o ...

Helgoland
, and some of the islands in the
Rhine ), Surselva Surselva Region is one of the eleven administrative districts Administrative division, administrative unitArticle 3(1). , country subdivision, administrative region, subnational entity, first-level subdivision, as well as many s ...

Rhine
-
Scheldt The Scheldt ( ; french: Escaut ; wa, Escô; nl, Schelde ) is a river that flows through northern France, western Belgium, and the southwestern part of Netherlands, the Netherlands, with its mouth at the North Sea. Its name is derived from an ...

Scheldt
estuary, which are in zone 9, to zone 5 around
Suwałki Suwałki ( lt, Suvalkai; yi, סואוואַלק, ) is a city in northeastern Poland Poland ( pl, Polska ), officially the Republic of Poland ( pl, Rzeczpospolita Polska, links=no ), is a country located in Central Europe. It is divided ...

Suwałki
,
Podlachia Podlachia or Podlasie, ( pl, Podlasie, be, Падляшша ''Padliašša'', lt, Palenkė, uk, Підляшшя ''Pidliashshia'') is a historical region in the eastern part of Poland. Between 1513 and 1795 it was a voivodeship with the capital i ...

Podlachia
on the far eastern border between
Poland Poland, officially the Republic of Poland, is a country located in Central Europe. It is divided into 16 Voivodeships of Poland, administrative provinces, covering an area of , and has a largely Temperate climate, temperate seasonal cli ...

Poland
and
Lithuania Lithuania (; lt, Lietuva ), officially the Republic of Lithuania ( lt, Lietuvos Respublika, links=no), is a country in the Baltic region The terms Baltic Sea Region, Baltic Rim countries (or simply Baltic Rim), and the Baltic Sea countr ...
. Some isolated, high elevation areas of the
Alps The Alps ; german: Alpen ; it, Alpi ; rm, Alps; sl, Alpe ) are the highest and most extensive mountain range A mountain range is a series of mountains ranged in a line and connected by high ground. A mountain system or mountain belt ...

Alps
and
Carpathians The Carpathian Mountains or Carpathians () are a range of mountains forming an arc throughout Central and Eastern Europe Central and Eastern Europe is a term encompassing the countries in Central Europe Central Europe is the central regio ...
may even go down to zone 3 or 4. An extreme example of a cold sink is ,
Bavaria Bavaria (; German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citizens of Germany, see also German nationality law * German language ...

Bavaria
which is at least in zone 3. Another notable example is , a small village in the
Polish Polish may refer to: * Anything from or related to Poland Poland ( pl, Polska ), officially the Republic of Poland ( pl, Rzeczpospolita Polska, links=no ), is a country located in Central Europe. It is divided into 16 Voivodeships of Pol ...

Polish
Carpathians The Carpathian Mountains or Carpathians () are a range of mountains forming an arc throughout Central and Eastern Europe Central and Eastern Europe is a term encompassing the countries in Central Europe Central Europe is the central regio ...
, which regularly reaches during winter on calm nights when cold and heavy airmasses from the surrounding Gorce and
Tatra Mountains The Tatra Mountains (), Tatras, or Tatra (''Tatry'' either in Slovak language, Slovak () or in Polish language, Polish () - ''plurale tantum''), is a mountain range that forms a natural border between Slovakia and Poland. They are the highest m ...

Tatra Mountains
descend down the slopes to this low-lying valley, creating extremes which can be up to colder than nearby
Nowy Targ Nowy Targ ( la, Novum Forum, sk, Nový Targ, german: Neumarkt, yi, ניימארקט ''Naymarkt,'' Goral: ''Miasto/Nowý Targ'') is a town in southern Poland with 34,000 inhabitants (2006). It is the capital of Goralscyzna and the Podhale region ...

Nowy Targ
or Białka Tatrzańska, which are both higher up in elevation. Waksmund is in zone 3b while nearby
Kraków Kraków (), also written in English as Krakow and traditionally known as Cracow, is the second-largest and one of the oldest cities in Poland. Situated on the Vistula River The Vistula (; pl, Wisła, , german: Weichsel) is the longest ri ...

Kraków
, only to the north and lower is in zone 6a. These examples prove that local topography can have a pronounced effect on temperature and thus on what is possible to grow in a specific region.


Southern Europe

The southern European marker plant for climate as well as cultural indicator is the
olive tree The olive, known by the botanical name ''Olea europaea'', meaning "European olive", is a species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit o ...

olive tree
, which cannot withstand long periods below freezing so its cultivation area matches the cool winter zone. The
Mediterranean Sea The Mediterranean Sea is a connected to the , surrounded by the and almost completely enclosed by land: on the north by and and , on the south by , and on the east by the . The Sea has played a central role in the . Although the Mediterrane ...
acts as a temperature regulator, so this area is generally warmer than other parts of the continent; except in mountainous areas where the sea effect lowers, it belongs in zones 8–10; however, southern Balkans (mountainous Western and Eastern
Serbia Serbia (, ; Serbian Serbian may refer to: * someone or something related to Serbia, a country in Southeastern Europe * someone or something related to the Serbs, a South Slavic people * in both meanings, depending on the context, it may ref ...

Serbia
, continental
Croatia , image_flag = Flag of Croatia.svg , image_coat = Coat of arms of Croatia.svg , anthem = "Lijepa naša domovino ''Lijepa naša domovino'' (; ) is the national anthem A national anthem is a song that ...

Croatia
, and
Bulgaria Bulgaria (; bg, България, Bǎlgariya), officially the Republic of Bulgaria ( bg, Република България, links=no, Republika Bǎlgariya, ), is a country in Southeast Europe. It is bordered by Romania to the north, Serbia ...

Bulgaria
) are colder in winter and are in zones 6–7. The Croatian (
Dalmatia Dalmatia (; hr, Dalmacija ; it, Dalmazia; see #Name, names in other languages) is a region on the east shore of the Adriatic Sea, a narrow belt stretching from the island of Rab in the north to the Bay of Kotor in the south. The Dalmatian Hin ...

Dalmatia
n) coast,
Albania Albania ( ; sq, Shqipëri or Shqipëria), officially the Republic of Albania ( sq, Republika e Shqipërisë), is a country in Southeastern Europe Southeast Europe or Southeastern Europe () is a geographical subregion A subregion is a par ...

Albania
, and northern
Greece Greece ( el, Ελλάδα, Elláda, ), officially the Hellenic Republic, is a country located in Southeastern Europe Southeast Europe or Southeastern Europe () is a geographical subregion A subregion is a part of a larger region In geogr ...

Greece
are in zones 8–9, as are central-northern
Italy Italy ( it, Italia ), officially the Italian Republic ( it, Repubblica Italiana, links=no ), is a country consisting of a peninsula delimited by the Alps The Alps ; german: Alpen ; it, Alpi ; rm, Alps; sl, Alpe ) are the highest ...

Italy
(hills and some spots in
Po Valley The Po Valley, Po Plain, Plain of the Po, or Padan Plain ( it, Pianura Padana , or ''Val Padana'') is a major geographical feature of Northern Italy Northern Italy ( it, Italia settentrionale, it, Nord Italia, label=none, it, Alta Italia, ...
are however colder) and southern
France France (), officially the French Republic (french: link=no, République française), is a transcontinental country This is a list of countries located on more than one continent A continent is one of several large landmasses ...

France
; Central
Iberia The Iberian Peninsula , ** * Aragonese language, Aragonese and Occitan language, Occitan: ''Peninsula Iberica'' ** ** * french: Péninsule Ibérique * mwl, Península Eibérica * eu, Iberiar penintsula also known as Iberia, is a penin ...

Iberia
is 8–9 (some highland areas are slightly colder). The
Spanish Spanish may refer to: * Items from or related to Spain: **Spaniards, a nation and ethnic group indigenous to Spain **Spanish language **Spanish cuisine Other places * Spanish, Ontario, Canada * Spanish River (disambiguation), the name of several ...

Spanish
and
Portuguese Portuguese may refer to: * anything of, from, or related to the country and nation of Portugal ** Portuguese cuisine, traditional foods ** Portuguese language, a Romance language *** Portuguese dialects, variants of the Portuguese language ** Portug ...

Portuguese
Atlantic coast, much of
Andalusia Andalusia (, ; es, Andalucía ) is the southernmost autonomous community eu, autonomia erkidegoa ca, comunitat autònoma gl, comunidade autónoma oc, comunautat autonòma an, comunidat autonoma ast, comunidá autónoma , alt_name ...
and
Murcia Murcia (, , ) is a city in south-eastern Spain , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = , national_anthem = , image_map ...
, coastal and slightly inland southern
Valencian Community The Valencian Community ( ca-valencia, Comunitat Valenciana, es, Comunidad Valenciana), or simply Valencia ( ca-valencia, València, link=no, es, Valencia, link=no), is an Autonomous communities of Spain, autonomous community of Spain. It is t ...
, a part of coastal
Catalonia Catalonia (; ca, Catalunya ; Aranese, Aranese Occitan: ''Catalonha'' ; es, Cataluña ) is an Autonomous communities of Spain, autonomous community in the northeastern corner of Spain, designated as a ''nationalities and regions of Spain, na ...

Catalonia
, the
Balearic Islands The Balearic Islands ( , also , ; ca, Illes Balears ; es, Islas Baleares ) are an archipelago An archipelago ( ), sometimes called an island group or island chain, is a chain, cluster or collection of islands, or sometimes a sea contai ...

Balearic Islands
, southwestern
Sardinia Sardinia ( ; it, Sardegna ; sc, Sardigna or ) is the second-largest island in the Mediterranean Sea The Mediterranean Sea is a connected to the , surrounded by the and almost completely enclosed by land: on the north by and and , ...

Sardinia
, most of
Sicily (man) it, Siciliana (woman) , population_note = , population_blank1_title = , population_blank1 = , demographics_type1 = Ethnicity , demographics1_footnotes = , demographi ...

Sicily
, coastal southern Italy, some areas around
Albania Albania ( ; sq, Shqipëri or Shqipëria), officially the Republic of Albania ( sq, Republika e Shqipërisë), is a country in Southeastern Europe Southeast Europe or Southeastern Europe () is a geographical subregion A subregion is a par ...

Albania
, coastal Cyprus and southwestern Greece are in zone 10. In Europe, the zone 11a is limited only to a few spots. In the Iberian Peninsula, it can be found on the southern coast, namely in populated
Spanish Spanish may refer to: * Items from or related to Spain: **Spaniards, a nation and ethnic group indigenous to Spain **Spanish language **Spanish cuisine Other places * Spanish, Ontario, Canada * Spanish River (disambiguation), the name of several ...

Spanish
areas such as the cities of
Almería Almería (, also , ) is a city in Andalusia, Spain, located in the southeast of Spain on the Mediterranean Sea, and is the capital of the province of Almería, province of the same name. Abd al-Rahman III founded the Alcazaba of Almería, Alcazaba ...

Almería
,
Adra The Adventist Development and Relief Agency International (ADRA or ADRA International) is a humanitarian agency operated by the Seventh-day Adventist Church for the purpose of providing individual and community development and disaster relief. It ...
, Nerja, Málaga, Marbella and in a strip of coastal land between Tarifa and Punta Carnero, Spain, Punta Carnero in the province of Cádiz. In Portugal, zone 11a can be found in the Southwest on a few unpopulated sites around the municipalities of Lagos, Portugal, Lagos and Vila do Bispo. The Mediterranean islands of Malta, Lampedusa and Linosa belong to zone 11a as well as a few areas on the southernmost coast of Cyprus. The Balkan area is also more prone to cold snaps and episodes of unseasonable warmth. For instance, despite having similar daily means and temperature amplitudes to Nantucket, Massachusetts for each month, Sarajevo has recorded below-freezing temperatures in every month of the year.


Macaronesia

Macaronesia consists of four archipelagos: The Azores, the Canary Islands, Cape Verde and Madeira. At lower altitudes and coastal areas, the
Portuguese Portuguese may refer to: * anything of, from, or related to the country and nation of Portugal ** Portuguese cuisine, traditional foods ** Portuguese language, a Romance language *** Portuguese dialects, variants of the Portuguese language ** Portug ...

Portuguese
Azores and Madeira belong to zones 11a/11b and 11b/12a respectively. The Azores range from 9a to 11b and Madeira ranges from 9b to 12a, 9a and 9b found inland on the highest altitudes such as the Mount Pico in the Azores or Pico Ruivo in Madeira. The
Spanish Spanish may refer to: * Items from or related to Spain: **Spaniards, a nation and ethnic group indigenous to Spain **Spanish language **Spanish cuisine Other places * Spanish, Ontario, Canada * Spanish River (disambiguation), the name of several ...

Spanish
Canary Islands are generally part of zones 11b/12a in lower altitudes and coastal areas, reaching up to 12b in the southernmost coastal parts of the islands of Tenerife, Gran Canaria, La Palma and El Hierro. The Canary Islands hardiness zones range from 7a to 12b depending on the altitude, with the Teide peak being at 7a/7b for its very high altitude of , being also the highest peak of Macaronesia. The Cape Verde islands, inside the Tropics, have hardiness zones that range from 12 to 13 in the coastal areas, while the lowest hardiness zone is found in the island of Fogo, Cape Verde, Fogo, in the country's highest peak Pico do Fogo.


American Horticultural Society heat zones

In addition to the USDA Hardiness zones there are
American Horticultural Society The American Horticultural Society (AHS) is a nonprofit, membership-based organization that promotes excellence in American horticulture Horticulture is the art of cultivating plants in gardens to produce food and medicinal ingredients, or for comf ...
(AHS) heat zones. The criterion is the average number of days per year when the temperature exceeds . The AHS Heat Zone Map for the US is available on the American Horticultural Society website.


South Africa

South Africa has five horticultural or climatic zones. The zones are defined by minimum temperature.


Effects of climate change

The USDA map published in 2012 shows that most of the US has become a half zone (5 °F) hotter in winter compared to the 1990 release. Research in 2016 suggests that USDA plant hardiness zones will shift even further northward under climate change.


See also

*Agriculture *Tropics *Subtropics *Gardening *Hardiness (plants) *Geographical zone


References


Bibliography

*


External links

{{External links, date=October 2012
Hardiness Zone maps for several continentsInteractive USDA Plant Hardiness Zone MapSunset Magazine Garden Climate Zone MapFreeze/Frost data from NOAAPlant Hardiness Data
(Canada)
Plant Hardiness Zones of Canada – Interactive Map
Agricultural terminology Horticulture Climate zones Geographic classifications