Hardiness zone

A hardiness zone is a geographic area defined to encompass a certain range of climatic conditions relevant to plant growth and survival.

The original and most widely-used system, developed by the United States Department of Agriculture (USDA) as a rough guide for landscaping and gardening, defines 13 zones by annual extreme minimum temperature. It has been adapted by and to other countries (such as Canada) in various forms.

Unless otherwise specified, "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 −1 °C (30.2 °F) to 3.9 °C (39.0 °F).

Other hardiness rating schemes have been developed as well, such as the UK Royal Horticultural Society and US Sunset Western Garden Book systems.

USDAHardiness 2012-2015 Scale
Temperature scale used to define USDA hardiness zones. These are annual extreme minimums (an area is assigned to a zone by taking the lowest temperature recorded there in a given year). As shown, the USDA uses a GIS dataset averaged over 1976 to 2005 for its United States maps.

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 the 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 (up to 12) and Puerto Rico (up to 13). The middle portion of the mainland and central and northern 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 (down to 1). The low latitude and often stable weather in Florida, the Gulf Coast, and southern Arizona and California, are responsible for the few episodes of severe cold relative to normal in those areas. The Pacific Ocean keeps the Pacific Northwest in warmer zones than nearby inland areas. The warmest zone in the 48 contiguous states is the Florida Keys (11b) and the coldest is in north-central Minnesota (3a).

Definitions

2012 USDA Plant Hardiness Zone Map (USA)
2012 update of the Hardiness Zone Map
Zone From To
0 a < −53.9 °C (−65 °F)
b −53.9 °C (−65 °F) −51.1 °C (−60 °F)
1 a −51.1 °C (−60 °F) −48.3 °C (−55 °F)
b −48.3 °C (−55 °F) −45.6 °C (−50 °F)
2 a −45.6 °C (−50 °F) −42.8 °C (−45 °F)
b −42.8 °C (−45 °F) −40 °C (−40 °F)
3 a −40 °C (−40 °F) −37.2 °C (−35 °F)
b −37.2 °C (−35 °F) −34.4 °C (−30 °F)
4 a −34.4 °C (−30 °F) −31.7 °C (−25 °F)
b −31.7 °C (−25 °F) −28.9 °C (−20 °F)
5 a −28.9 °C (−20 °F) −26.1 °C (−15 °F)
b −26.1 °C (−15 °F) −23.3 °C (−10 °F)
6 a −23.3 °C (−10 °F) −20.6 °C (−5 °F)
b −20.6 °C (−5 °F) −17.8 °C (0 °F)
7 a −17.8 °C (0 °F) −15 °C (5 °F)
b −15 °C (5 °F) −12.2 °C (10 °F)
8 a −12.2 °C (10 °F) −9.4 °C (15 °F)
b −9.4 °C (15 °F) −6.7 °C (20 °F)
9 a −6.7 °C (20 °F) −3.9 °C (25 °F)
b −3.9 °C (25 °F) −1.1 °C (30 °F)
10 a −1.1 °C (30 °F) +1.7 °C (35 °F)
b +1.7 °C (35 °F) +4.4 °C (40 °F)
11 a +4.4 °C (40 °F) +7.2 °C (45 °F)
b +7.2 °C (45 °F) +10 °C (50 °F)
12 a +10 °C (50 °F) +12.8 °C (55 °F)
b > +12.8 °C (55 °F)

History

The first attempts to create a geographical hardiness zone system were undertaken by two researchers at the Arnold Arboretum in Boston: the first was published in 1927 by Alfred Rehder,[1] and the second by Donald Wyman in 1938.[2] 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. 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.[3][4]

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 (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 islands by showing the downtown areas of several cities (e.g., Baltimore, Maryland; Washington, D.C. and Atlantic City, New Jersey) 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, that the American Horticultural Society now uses.[5]

In 2006, the Arbor Day Foundation 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.[6]

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.[7] Two new zones 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. 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.[8] The 2012 map was created digitally for the internet, and includes a ZIP Code zone finder and an interactive map.[9][10]

Selected U.S. cities

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

City Zone City Zone
Albuquerque, New Mexico 7b Oklahoma City, Oklahoma 7a
Anchorage, Alaska 4b/5a Omaha, Nebraska 5b
Atlanta, Georgia 8a Orlando, Florida 9b
Baltimore, Maryland 7b/8a Panama City Beach, Florida 9a
Boston, Massachusetts 6b/7a Philadelphia, Pennsylvania 7a/7b
Buffalo, New York 6a Phoenix, Arizona 9b/10a
Burlington, Vermont 5a Pierre, South Dakota 4b/5a
Charleston, South Carolina 8b/9a Pittsburgh, Pennsylvania 6b
Charleston, West Virginia 6b Pocatello, Idaho 5b
Chicago, Illinois 6a Portland, Maine 5b
Charlotte, North Carolina 7b/8a Portland, Oregon 8b/9a
Chattanooga, Tennessee 7a/7b Providence, Rhode Island 6b
Columbus, Ohio 6a Quad Cities, Iowa/Illinois 5b
Dallas, Texas 8a/8b Raleigh, North Carolina 7b
Denver, Colorado 5b/6a Reno, Nevada 6b/7a
Detroit, Michigan 6b Roanoke, Virginia 7a/7b
Fairbanks, Alaska 2a Sacramento, California 9b
Hartford, Connecticut 6b Salt Lake City, Utah 7a/7b
Honolulu, Hawaii 12b San Antonio, Texas 8b/9a
Houston, Texas 9a San Diego, California 10a/10b
Indianapolis, Indiana 5b/6a San Francisco, California 10a/10b
Juneau, Alaska 6b/7a San Gabriel, California 10a
Kansas City, Missouri 6a/6b San Jose, California 9b/10a
Las Vegas, Nevada 9a San Juan, Puerto Rico 12b/13a
Los Angeles, California 10a/10b Savannah, Georgia 8b
Memphis, Tennessee 7b/8a Seattle, Washington 8b/9a
Miami, Florida 10b/11a Tampa, Florida 9b
Minneapolis, Minnesota 4b/5a Tucson, Arizona 9b
Nashville, Tennessee 7a Tuscaloosa, Alabama 8a
New Orleans, Louisiana 9b Utqiagvik, Alaska 2b
New York, New York 7a/7b Washington, D.C.[11] 7a/7b
Norfolk, Virginia 8a Wichita, Kansas 6b

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, 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 and Mojave and Chihuahuan inland deserts, thus an American gardener in such an area may only have to plan for several days 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; 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 and London, as well as lower latitude, hot summer climates like Charleston and Madrid. Farmers, gardeners, and landscapers in the former two must plan for entirely different growing seasons from those in the latter.

In the colder zones, another issue is that the hardiness scales do not take into account the reliability of snow cover. 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 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, located to the southwest in zone 5, it is sometimes difficult to cultivate plants adapted to the zone because of the unreliable snow cover.

Another problem is that many plants may survive in a locality but will not flower if the day length is insufficient or if they require vernalization (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.[9][3][12]

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 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.[13]

In addition, the Koppen 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.

Climate change projections

Recent research suggests that USDA plant hardiness zones will shift northward under climate change.[14]

Australian hardiness zones

The USDA hardiness zones are not used in Australia. The Australian National Botanic Gardens have devised another system more in keeping with Australian conditions.[15] 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 have no US equivalents.

There are problems with classifications of this type: the spread of weather stations is insufficient to give clear zones and too many places with different climates are lumped together. Only 738 Australian stations have records of more than ten years (one station per 98,491 hectares or 243,380 acres), though more populated areas have relatively fewer hectares per station. Local factors such as aspect, altitude, proximity to the sea also complicate the matter. For example, Mount Isa 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. Likewise, Sydney residents are split between zones 3a and 4b. Most other cities have similar problems. Different locations in the same city are suitable for different plants, making it hard to draw a meaningful map without publishing a list of weather stations and their zone classification to allow best use of local conditions.

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.[16] This index comes from a formula originally developed by Ouellet and Sherk in the mid-1960s.[17][18][19]

The formula used:

Y = −67.62 + 1.734X1 + 0.1868X2 + 69.77X3 + 1.256X4 + 0.006119X5 + 22.37X6 – 0.01832X7

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.

City Zone[16]
Calgary 4a
Edmonton 4a
Halifax 6b
Montreal 6a
Ottawa 5b
Saskatoon 3b
St. John's 6a
Toronto 7a
Vancouver 8b
Winnipeg 4a
Yellowknife 0a

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.[8]

European hardiness zones

British Isles

UK zonemap
Britain and Ireland's hardiness zones

Owing to the moderating effect of the North Atlantic Current on the Irish and British temperate maritime climate, Britain, and Ireland even more so, have milder winters than their northerly position would otherwise afford. This means that the hardiness zones relevant to Britain and Ireland are quite high, from 7 to 10, as shown below.

  • 7. In Scotland the Grampians, Highlands and locally in the Southern Uplands, in England the Pennines, and in Wales the highest part of Snowdonia.
  • 8. Most of England, Wales and Scotland, parts of central Ireland, and Snaefell on the Isle of Man.
  • 9. Most of western and southern England and Wales, western Scotland, also a very narrow coastal fringe on the east coast of Scotland and northeast England (within 5 kilometres (3.1 mi) of the North Sea), London, the West Midlands Urban Area, most of Ireland, and most of the Isle of Man.
  • 10. Very low-lying coastal areas of the southwest of Ireland and the Isles of Scilly.

USDA zones do not work particularly well in the UK as they are designed for a continental climate.[20] The cooler UK summers must be considered. New growth may be insufficient or fail to harden off affecting winter survival.[20]

In 2012 the United Kingdom's Royal Horticultural Society introduced new hardiness ratings for plants, from H7, the hardiest (tolerant of temperatures below −20 °C (−4 °F)) to H1a (needing temperatures above 15 °C (59 °F)).[21] 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.[21]

Scandinavia

Scandinavia lies at the same latitude as Alaska or Greenland, but the effect of the warm North Atlantic Current is even more pronounced here than it is in Britain and Ireland. Save for a very small spot near Karasjok, Norway, which is in zone 2, nowhere in the Arctic part of Scandinavia does it get below zone 3. The Faroe Islands, at 62–63°N are in zone 8, as are the outer Lofoten Islands at 68°N. Tromsø, a coastal city in Norway at 70°N, is in zone 7, and even Longyearbyen, the northernmost true city in the world at 78°N, is still in zone 5. All these coastal locations have one thing in common, though, which are cold, damp summers, with temperatures rarely exceeding 20 °C (68 °F), or 15 °C (59 °F) in Longyearbyen. This shows the importance of taking heat zones into account for better understanding of what may or may not grow.

Osterlengarden
A garden in Simrishamn, southern Sweden.

In Sweden and Finland generally, at sea level to 500 metres (1,600 ft), zone 3 is north of the Arctic Circle, including cities like Karesuando, Pajala, and Rovaniemi. 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 64–65°N, with cities such as Oulu and Jokkmokk, zone 5 (south to 61–62°N) contains cities such as Tampere, Umeå, and Östersund. Zone 6 covers the south of mainland Finland, Sweden north of 60°N, and the high plateau of Småland further south. Here one will find cities such as Gävle, Örebro, Sundsvall, and Helsinki. The Åland Islands, as well as coastal southern Sweden, and the Stockholm area are in zone 7. The west coast of Sweden (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 southeast coast of Sweden has a colder winter due to the absence of the Gulf Stream.

Denmark is in zones 9a, 8b, and 8a.[22]

Central Europe

Central Europe is a good example of a transition from an oceanic climate to a continental climate, which can be noticed immediately when looking at the hardiness zones, which tend to decrease mainly eastwards instead of northwards. Also, the plateaux 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 in the Shetland Islands 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 coast, with the exception of some of the Frisian Islands (notably Vlieland and Terschelling), the island of Helgoland, and some of the islands in the Rhine-Scheldt estuary, which are in zone 9, to zone 5 around Suwałki, Podlachia on the far eastern border between Poland and Lithuania. Some isolated, high elevation areas of the Alps and Carpathians may even go down to zone 3 or 4. An extreme example of a cold sink is Funtensee, Bavaria which is at least in zone 3 and maybe even in zone 1 or 2. Another notable example is Waksmund, a small village in the Polish Carpathians, which regularly reaches −35 °C (−31 °F) during winter on calm nights when cold and heavy airmasses from the surrounding Gorce and Tatra Mountains descend down the slopes to this low-lying valley, creating extremes which can be up to 10 °C (18 °F) colder than nearby Nowy Targ or Białka Tatrzańska, which are both higher up in elevation. Waksmund is in zone 3b while nearby Kraków, only 80 km (50 mi) to the north and 300 m (980 ft) 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, which cannot withstand long periods below freezing so its cultivation area matches the cool winter zone. The Mediterranean Sea 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, continental Croatia, and Bulgaria) are colder in winter and are in zones 6–7. The Croatian (Dalmatian) coast, Albania, and northern Greece are in zones 8–9, as are central-northern Italy (hills and some spots in Po Valley are however colder) and southern France; Central Iberia is 8–9 (some highland areas are slightly colder). The Spanish and Portuguese Atlantic coast, most of Andalusia and Murcia, almost all the Valencian Community, a part of Catalonia, the Balearic Islands, southwestern Sardinia, most of Sicily, coastal southern Italy, and southwestern Greece are in zone 10. The islands of Malta and Lampedusa belong to zone 11a and the southernmoust zone of Spain (Cádiz, Málaga, where the cultivation of mango, avocado or papaya are extended) belong to zone 11a.[23] Also, a few areas on the southernmost coast of Cyprus are inside zone 11a.

Selected European cities

The table below provides hardiness zone data for selected European cities (based on climatological data):[24][25][26]

City Zone City Zone
Alicante, Spain 10b Almería, Spain 11a
Amsterdam, The Netherlands 8b Antwerp, Belgium 8
Barcelona, Spain 10a Belfast, Northern Ireland 9
Berlin, Germany 7b Bratislava, Slovakia 7b
Birmingham, England 9a Bucharest, Romania 6b
Cádiz, Spain 11a Cardiff, Wales 9
Belgrade, Serbia 8a Copenhagen, Denmark 8a
Dublin, Ireland 9a Düsseldorf, Germany 8
Edinburgh, Scotland 8b Gdańsk, Poland 7
Glasgow, Scotland 8b Hamburg, Germany 8a
Helsinki, Finland 6a Istanbul, Turkey 8b
Kaliningrad, Russia 6 Kiev, Ukraine 6a
Kraków, Poland 6 Lisbon, Portugal 10b
Las Palmas, Spain 12b A Coruña, Spain 10b
Ljubljana, Slovenia 7b London, England 9a
Madrid, Spain 9a Málaga, Spain 11a
Marseille, France 9a Milan, Italy 8b
Minsk, Belarus 5b Moscow, Russia 5a
Munich, Germany 7b Murmansk, Russia 5
Nicosia, Cyprus 10a/10b Oslo, Norway 6a
Simferopol, Ukraine 7a Palma, Spain 10a
Paris, France 8b Poznań, Poland 7a
Prague, Czech Republic 7a Reykjavík, Iceland 8a
Riga, Latvia 6a Rome, Italy 9b
Rovaniemi, Finland 4 Saint Petersburg, Russia 5b
Sarajevo, Bosnia and Herzegovina 7b Santander, Spain 10a
Sicily (Catania, Italy) 10a Simrishamn, Sweden 8a
Sochi, Russia 9 Sofia, Bulgaria 7a
Stockholm, Sweden 6b Strasbourg, France 7
Tallinn, Estonia 6b Tuapse, Russia 8
Tórshavn, Faroe Islands 7-8 Tromsø, Norway 7
Trondheim, Norway 6 Umeå, Sweden 5
Valencia, Spain 10b Valletta, Malta 11a
Vienna, Austria 8a Vilnius, Lithuania 6
Vorkuta, Russia 2 Warsaw, Poland 6b
Wroclaw, Poland 7a Zagreb, Croatia 8a
Zürich, Switzerland 8a Zaragoza, Spain 9b

American Horticultural Society heat zones

In addition to the USDA Hardiness zones there are American Horticultural Society (AHS) heat zones.

The criterion is the average number of days per year when the temperature exceeds 30 °C (86 °F). The AHS Heat Zone Map for the US is available on the American Horticultural Society website.[27]

Zone From To
1 < 1
2 1 7
3 8 14
4 15 30
5 31 45
6 46 60
7 61 90
8 91 120
9 121 150
10 151 180
11 181 210
12 >210

European cities (AHS heat zones)

City Zone City Zone
Amsterdam, The Netherlands 2 Antwerp, Belgium 2
Belfast, Northern Ireland 1 Berlin, Germany 3
Birmingham, England 2 Bratislava, Slovakia 4
Bucharest, Romania 6 Cardiff, Wales 1
Copenhagen, Denmark 2 Cork, Ireland 1
Derry, Northern Ireland 1 Dublin, Ireland 1
Düsseldorf, Germany 3 Edinburgh, Scotland 1
Gdańsk, Poland 2 Galway, Ireland 1
Glasgow, Scotland 1 Hamburg, Germany 2
Helsinki, Finland 2 Istanbul, Turkey 6
Kaliningrad, Russia 2 Kiev, Ukraine 4
Kraków, Poland 4 Lisbon, Portugal 7
Ljubljana, Slovenia 6 London, England 2
Madrid, Spain 7 Málaga, Spain 7
Marseille, France 7 Milan, Italy 6
Minsk, Belarus 3 Moscow, Russia 2
Munich, Germany 3 Murmansk, Russia 1
Nicosia, Cyprus 9 Oslo, Norway 2
Oulu, Finland 1 Palma, Spain 8
Paris, France 3 Perm, Russia 3
Prague, Czech Republic 3 Reykjavík, Iceland 1
Riga, Latvia 2 Rome, Italy 7
Rovaniemi, Finland 1 Saint Petersburg, Russia 2
Sarajevo, Bosnia and Herzegovina 5 Santander, Spain 3
Simrishamn, Sweden 1 Sochi, Russia 6
Sofia, Bulgaria 6 Stockholm, Sweden 2
Strasbourg, France 4 Tallinn, Estonia 2
Tuapse, Russia 7 Tórshavn, Faroe Islands 1
Tromsø, Norway 1 Trondheim, Norway 1
Umeå, Sweden 1 Vienna, Austria 4
Vilnius, Lithuania 2 Vorkuta, Russia 1
Warsaw, Poland 3 Zürich, Switzerland 4

South Africa

South Africa has five horticultural or climatic zones.[28]

See also

References

  1. ^ Fernald, M. L. (1927). Rehder, Alfred (ed.). "Rehder's Manual of Cultivated Trees and Shrubs". Rhodora. 29 (339): 48–51. JSTOR 23298457.
  2. ^ Wyman, Donald (1938). Hedges, Screens & Windbreaks: Their Uses, Selection and Care. McGraw-Hill.
  3. ^ a b "History of Plant Hardiness Zone Maps – The Rest of the Story". Plant Delights Nursery. Retrieved 2018-06-03.
  4. ^ Del Tredici, Peter (1990). "The New USDA Plant Hardiness Zone Map" (PDF). Arnoldia. 50 (3): 16–20 – via Harvard University.
  5. ^ "USDA Hardiness Zone Map". American Horticultural Society. Archived from the original on 8 December 2017. Retrieved 8 December 2017.
  6. ^ "New arborday.org Hardiness Zone Map reflects warmer climate : Latest hardiness zones, based on most current temperature data available, suggest up-to-date choices for best trees to plant". Archived from the original on 2007-12-28. Retrieved 2007-12-27.
  7. ^ "USDA Plant Hardiness Zone Map, 2012". Agricultural Research Service. U.S. Department of Agriculture. Archived from the original on 24 October 2017. Retrieved 7 December 2017.
  8. ^ a b "What's New | USDA Plant Hardiness Zone Map". Agricultural Research Service. U.S. Department of Agriculture. Archived from the original on 19 October 2017. Retrieved 7 December 2017.
  9. ^ a b "About | USDA Plant Hardiness Zone Map". planthardiness.ars.usda.gov. Retrieved 2018-06-03.
  10. ^ "History of USDA Hardiness Zones". www.weekendgardener.net. Retrieved 2018-06-03.
  11. ^ "7a" areas not part of downtown Washington
  12. ^ McKenney, Daniel W.; Pedlar, John H.; Lawrence, Kevin; Campbell, Kathy; Hutchinson, Michael F. (2007-12-01). "Beyond Traditional Hardiness Zones: Using Climate Envelopes to Map Plant Range Limits". BioScience. 57 (11): 929–937. doi:10.1641/B571105. ISSN 1525-3244.
  13. ^ Sunset National Garden Book. Sunset Books Inc. Menlo Park, California (1997)
  14. ^ Parker, Lauren E.; Abatzoglou, John T. (2016). "Projected changes in cold hardiness zones and suitable overwinter ranges of perennial crops over the United States". Environmental Research Letters. 11 (3): 034001. doi:10.1088/1748-9326/11/3/034001. ISSN 1748-9326.
  15. ^ "Plant Hardiness Zones for Australia". Archived from the original on 2010-12-10. Retrieved 2010-11-11.
  16. ^ a b "Natural Resources Canada – Plant Hardiness of Canada". Natural Resources Canada – Plant Hardiness of Canada. Government of Canada. Archived from the original on 29 June 2006. Retrieved 7 April 2018.
  17. ^ Ouellet, C.E., Sherk, L.C. 1967a. Woody ornamental plant zonation I. Indices of winter hardiness. Can J. Plant Sci. 47:231–238.
  18. ^ Ouellet, C.E., Sherk, L.C. 1967b. Woody ornamental plant zonation. II. Suitability indices of localities. Can J. Plant Sci. 47: 339–349.
  19. ^ Ouellet, C.E., Sherk, L.C. 1967c. Woody ornamental plant zonation III. Suitability map for the probable winter survival of ornamental trees and shrubs. Can J. Plant Sci. 47: 351–358.
  20. ^ a b Martin Crawford (2010). Creating a forest garden : working with nature to grow edible crops. Green Books. p. 13. ISBN 9781900322621.
  21. ^ a b "RHS hardiness rating". RHS hardiness rating. Royal Horticultural Society. Archived from the original on 25 September 2016. Retrieved 24 September 2016.
  22. ^ "Denmark Interactive Plant Hardiness Zone Map". www.plantmaps.com. Archived from the original on 11 October 2017. Retrieved 1 May 2018.
  23. ^ "Archived copy". Archived from the original on 2016-03-05. Retrieved 2015-06-09.CS1 maint: Archived copy as title (link)
  24. ^ "Hardiness zone – Gardenology.org – Plant Encyclopedia and Gardening wiki". Gardenology.org. Archived from the original on 2012-10-03. Retrieved 2012-10-13.
  25. ^ "Europa Hardiness zone map". Backyardgardener.com. Archived from the original on 2012-08-15. Retrieved 2012-10-13.
  26. ^ "Hardiness Zones". Havlis.cz. Archived from the original on 2012-05-04. Retrieved 2012-10-13.
  27. ^ "AHS Plant Heat Zone Map". American Horticultural Society. Archived from the original on 2017-05-16. Retrieved 2017-05-26.
  28. ^ PlantZAfrica 2016, Horticultural Zones

Bibliography

External links

Andreas, Pennsylvania

Andreas (pronounced ANN-dreez) is a village in the southeast corner of Schuylkill County, Pennsylvania, in West Penn Township on Route 895. A small part of Andreas is also in East Penn Township in Carbon County. The Lizard Creek flows eastward through the village to the Lehigh River. Andreas lies at the northern foot of Blue Mountain in ZIP code 18211.

The village takes its name from Andreas, Isle of Man.The village and surrounds are geographically closer to Allentown and Bethlehem than to the Schuylkill County seat at Pottsville. Because of this, and its location on the Carbon County border, it is often seen as a suburb/exurb of the Lehigh Valley region.Andreas is served by the Mantzville exchanges (386 and 818) in area code 570 and (205) in area code 272, though residents in the eastern section of the village can be assigned a number in the Lehighton (377) exchange of area code 610.

Andreas is surrounded by slate quarries. Galen Glen Winery is located one mile north of the village and is included in the Lehigh Valley Wine Trail of the Lehigh Valley AVA. The local hardiness zone is 6a. [1]

Begonia grandis

Begonia grandis, the hardy begonia, is a plant in the begonia family, Begoniaceae. It is a herbaceous plant with alternate, simple leaves on arching stems. The flowers are pink or white, borne in dichotomously branching cymes from late summer through fall in USDA U.S. Hardiness Zone 7. As the common name "hardy begonia" implies, it is winter hardy in some temperate regions.

It can overwinter well in hardiness zone 9a in southwestern Japan as tuberous roots or bulbils (bulbils are formed in axils). Above-ground parts of this plant eventually die as temperature lowers. However, it is generally regarded as hardy to zones 6-7.

Climate of Dallas

The city of Dallas has a humid subtropical climate (Köppen climate classification: Cfa) that is characteristic of the Southern Plains of the United States. Dallas experiences distinct four seasons with mild winters and hot summers.

During the winter season, daytime highs above 65 °F (18 °C) are not unusual. On the other hand, a couple of times each year, warm and humid air from the south overrides cold, dry air, leading to freezing rain, which often causes major disruptions in the city if the roads and highways become slick. Due to the city's location inland from the Gulf Coast, the city's climate is mildly continental: it is characterized by a relatively wide annual temperature range, as well as significant weather variations in a given month.

Spring and autumn bring pleasant weather to the area. Vibrant wildflowers (such as the bluebonnet, Indian paintbrush and other flora) bloom in spring and are planted around the highways throughout Texas. Springtime weather can be quite volatile, but temperatures themselves are mild. The weather in Dallas is also generally pleasant between late September and early December, and unlike springtime, major storms rarely form in the area.

In the spring, cool fronts moving south from Canada collide with warm, humid air streaming in from the Gulf Coast. When these fronts meet over north central Texas, severe thunderstorms are generated with spectacular lightning shows, torrents of rain, hail, and occasionally, tornadoes (Dallas is located at the lower-end of the Tornado Alley). The U.S. Department of Agriculture places Dallas in Plant Hardiness Zone 8a.Summers are hot, with temperatures approaching those of desert and semidesert locations of similar latitude. Heat waves can be severe. During the summer, the region receives warm and dry winds from the north and west. The city's all-time recorded high temperature is 113 °F (45 °C) during the Heat Wave of 1980, while the all-time recorded low is −8 °F (−22 °C) 1899. The average daily low in Dallas is 57.1 °F (13.9 °C) and the average daily high in Dallas is 76.7 °F (24.8 °C). Dallas receives approximately 37.1 inches (942 mm) of equivalent rain per year.

Fennville AVA

The Fennville AVA is an American Viticultural Area located in Allegan County, Michigan. Entirely contained within the larger Lake Michigan Shore AVA, the Fennville AVA borders Lake Michigan on the west, the Kalamazoo River on the north, a game reserve to the east, and the Black River on the south. The soil in the Fennville area is different from surrounding areas, primarily glacial sandy soils. The area's climate is moderated by the nearby Lake Michigan, and few days in the summer growing season exceed 90 °F (32 °C). Grape growers in the area have had success with both Vitis vinifera and Vitis labrusca wine grapes. The hardiness zone is 6a.

Grand Valley AVA

The Grand Valley AVA is an American Viticultural Area located in Mesa County, Colorado, surrounding the cities of Grand Junction and Palisade. The AVA is defined as the irrigated agricultural area served by canals within the Grand Valley of the Colorado River.

The AVA encompasses 75,990 acres (30,750 ha). The terrain is varied, ranging from alluvial soils along the Colorado River to stony and loamy soils on mesas. Climate is high desert, subject to swings of temperature and wide diurnal variation. The AVA enjoys the most temperate climate within the state of Colorado, with the USDA cold hardiness zone ranging from 6 to 7. The eastern part of the AVA near the town of Palisade has consistent breezes that provide good air drainage, reducing the risk of frost. During a typical growing season, the valley is hot and dry with lots of sunny days.

Viticulture began in the area in the late 19th century. State Governor George A. Crawford planted a 60 acres (24 ha) vineyard in the Grand Valley in 1890. Most of the Colorado grape production is from the Grand Valley AVA and hence many wineries are located there. Vineyards in the valley are planted at elevations as high as 4,700 feet (1,400 m) above sea level. However, the continental climate somewhat limits the varieties used in grape production and not all varieties produce adequate yields. Grape varieties planted within the AVA vary widely and average yields are relatively low at about 2.5 tons/acre. Wine styles range from dry white and red wines, to semi-sweet and dessert wines, and even icewine.In 2018, Wine Enthusiast Magazine named Colorado's Grand Valley AVA one of the Top Ten wine travel destinations in the world.

Hardiness (plants)

Hardiness of plants describes their ability to survive adverse growing conditions. It is usually limited to discussions of climatic adversity. Thus a plant's ability to tolerate cold, heat, drought, flooding, or wind are typically considered measurements of hardiness. Hardiness of plants is defined by their native extent's geographic location: longitude, latitude and elevation. These attributes are often simplified to a hardiness zone. In temperate latitudes, the term most often describes resistance to cold, or "cold-hardiness", and is generally measured by the lowest temperature a plant can withstand. Hardiness of a plant is usually divided into two categories: tender, and hardy. Some sources also use the erroneous terms "Half-hardy" or "Fully hardy". Tender plants are those killed by freezing temperatures, while hardy plants survive freezing—at least down to certain temperatures, depending on the plant. "Half-hardy" is a term used sometimes in horticulture to describe bedding plants which are sown in heat in winter or early spring, and planted outside after all danger of frost has passed. "Fully hardy" usually refers to plants being classified under the Royal Horticultural Society classifications, and can often cause confusion to those not using this method.Plants vary a lot in their tolerance of growing conditions. The selective breeding of varieties capable of withstanding particular climates forms an important part of agriculture and horticulture. Plants adapt to changes in climate on their own to some extent. Part of the work of nursery growers of plants consists of cold hardening, or hardening off their plants, to prepare them for likely conditions in later life.

Hudson River Region AVA

The Hudson River Region AVA is an American Viticultural Area around the Hudson River in eastern New York. The region is home to the oldest continuously operating winery in North America, the Brotherhood Winery, established in 1839. The oldest continuously cultivated vineyard in North America is also located in the Hudson River Region AVA, and is today operated by Benmarl Winery.

Most vineyards in the region are located within 2 miles (3.2 km) of the river. The Hudson River flows from north to south, and most vineyards are planted on hills on the western side of the river, where early morning sunshine can rapidly warm the vines. Ocean breezes channeled north up the river help to moderate the climate in the region, making it cooler in the summer and warmer in the winter than surrounding areas. The hardiness zone ranges from 7a to 6a.

The most important grape varieties in the area are French hybrids and cool-climate Vitis vinifera varieties.

Konjac

Konjac (or konjak, English: KOHN-yak) is a common name of the Asian plant Amorphophallus konjac (syn. A. rivieri), which has an edible corm (bulbo-tuber). It is also known as konjaku, konnyaku potato, devil's tongue, voodoo lily, snake palm, or elephant yam (though this name is also used for A. paeoniifolius).

It is native to Yunnan in China and cultivated in warm subtropical to tropical eastern Asia, from Japan and China south to Indonesia (USDA hardiness zone 6-11). It is a perennial plant, growing from a large corm up to 25 cm (10 in) in diameter. The single leaf is up to 1.3 m (4 ft) across, bipinnate, and divided into numerous leaflets. The flowers are produced on a spathe enclosed by a dark purple spadix up to 55 cm (22 in) long.

The food made from the corm of this plant is widely known in English by its Japanese name, konnyaku (yam cake), being cooked and consumed primarily in Japan. The two basic types of cake are white and black. Noodles made from konnyaku are called shirataki.

The corm of the konjac is often colloquially referred to as a yam, though it is not related to tubers of the family Dioscoreaceae.

Monticello AVA

The Monticello AVA is an American Viticultural Area located in the central Piedmont region of the Commonwealth of Virginia. It is named for Monticello, the historic home of Thomas Jefferson, located near the center of the area. The Monticello AVA includes most of the counties of Albemarle, Fluvanna, Greene, Orange, and Nelson. The area is nestled along the eastern slopes of the Blue Ridge Mountains and encompasses the small ridge known as the Southwest Mountains. There are approximately 30 varieties of grapes grown in the Monticello AVA. However, the most notable grapes grown in the area include Cabernet Franc, Chardonnay and Viognier. The hardiness zone is 7a except in some higher vineyards which are 6b.

North Fork of Long Island AVA

The North Fork of Long Island AVA is an American Viticultural Area located in eastern Suffolk County, New York. Authored by winemaker Richard Olsen-Harbich in 1985, it includes the entire North Fork of Long Island and the townships of Riverhead, Shelter Island, and Southold. The North Fork of Long Island is home to 40 wineries and 3,000 acres (1,200 ha) of planted vineyards. The local climate is heavily influenced by the presence of Long Island Sound, Peconic Bay, and the Atlantic Ocean. The maritime influences of these bodies of water help to moderate temperature fluctuations and extend the growing season up to a month longer than other regions in New York. The most planted grape varieties in the region are Merlot, Chardonnay, and Cabernet Franc. The hardiness zone is 7a.

Northern Neck George Washington Birthplace AVA

The Northern Neck George Washington Birthplace AVA is an American Viticultural Area in eastern portion of the state of Virginia. Wines made from grapes grown in Westmoreland, King George, Northumberland, Lancaster, and Richmond counties may use this appellation. The area is located on a peninsula of land between the Potomac and Rappahannock rivers in the Tidewater region of Virginia and known as the Northern Neck. This provides a climate which features more frost free days than the rest of Virginia. The tip of the Northern Neck is located at the Chesapeake Bay. The hardiness zone is 7b.

Ozark Mountain American Viticultural Area

The Ozark Mountain AVA is an American Viticultural Area located in northwest Arkansas, southern Missouri, and northeast Oklahoma. The sixth largest American Viticultural Area in total size, Ozark Mountain AVA covers 3,520,000 acres (1,424,493 ha). Five smaller AVAs have been established within its boundaries, to recognize those distinct regions whose climate, vineyard soil, or other growing conditions create unique areas for viticulture. The hardiness zone in the region varies from 6a to 7b.

Quercus phillyraeoides

Quercus phillyreoides is a species of plant in the genus Quercus. It is evergreen, withstands frost and can be grown in hardiness zone 7.

Ruscus aculeatus

Ruscus aculeatus, known as butcher's-broom, is a low evergreen Eurasian shrub, with flat shoots known as cladodes that give the appearance of stiff, spine-tipped leaves. Small greenish flowers appear in spring, and are borne singly in the centre of the cladodes. The female flowers are followed by a red berry, and the seeds are bird-distributed, but the plant also spreads vegetatively by means of rhizomes. It is native to Eurasia and some northern parts of Africa. Ruscus aculeatus occurs in woodlands and hedgerows, where it is tolerant of deep shade, and also on coastal cliffs. Likely due to its attractive winter/spring color, Ruscus aculeatus has become a fairly common landscape plant. It is also widely planted in gardens, and has spread as a garden escapee in many areas outside its native range. The plant grows well in zones 7 to 9 on the USDA hardiness zone map.The Latin specific epithet aculateus means “prickly”.

Simrishamn

Simrishamn is a locality and the seat of Simrishamn Municipality, Skåne County, Sweden with 6,527 inhabitants in 2010. Simrishamn is, despite its small population, for historical reasons normally still referred to as a city.

Simrishamn is a picturesque coastal town, built around the main street (Storgatan), that passes the market square, itself being the centre of the town. The climate of Simrishamn is mild, because it is warmed by the Gulf Stream, and the hardiness zone of Simrishamn is 8a, comparable to Paris, France.

Spiraea tomentosa

Spiraea tomentosa, commonly known as the steeplebush, meadowsweet, or hardhack, is a plant similar in characteristics to S. douglasii.

Spiraea tomentosa grows to up to four feet high, and prefers moist to wet soil and full sun. It blooms in summer. Individual Steeplebush flowers are about 1/16 of an inch wide and are arranged in narrow, pyramid-shaped clusters that can be up to eight inches long. Butterflies and other nectar-feeding insects find the flowers highly attractive. The flowers are followed by small, dry, brown fruit. It has a dense white-woolly tomentum which covers its stem and the underside of its leaves. It is noted for its astringent properties, which cause it to be used medicinally.

The hardiness zone for this plant is listed as zones 4 to 8. It is found natively in the eastern United States and Canada.

Sumneytown, Pennsylvania

Sumneytown is an unincorporated community on Route 63 in Marlborough Township, Montgomery County, Pennsylvania, United States. The Unami Creek forms its natural SE boundary with Salford and Upper Salford Townships and flows SW into the Perkiomen Creek. The historic Kings Highway passed through Sumneytown and the portion from there north to the Lehigh County line is named Geryville Pike today. The village was named for early settler Issac Sumney, who opened the Red Lion there in 1762. 63 starts just to the NW in Green Lane and proceeds SE to the Lansdale/North Wales area as Sumneytown Pike. In 1848 the Sumneytown and Spring House Turnpike was opened to Marlborough and resulted in an influx of tourism from the wealthy families of Philadelphia. This route is 63 to Kulpsville today. While Sumneytown has its own box post office with the zip code of 18084, some residents are served by the Green Lane PO with the zip of 18054.Sumneytown has a hot-summer humid continental climate (Dfa) and is located in hardiness zone 7a.

Sweet Sixteen (apple)

Sweet Sixteen is a cultivar of domesticated apple.

Virginia's Eastern Shore AVA

The Virginia's Eastern Shore AVA is an American Viticultural Area that includes a 70 miles (113 km) length of Virginia's Eastern Shore and consists of the counties of Accomack and Northampton. The topography in this AVA is mostly level and ranges from sea level to 50 feet (15 m) above sea level. The area is located on the southern end of the Delmarva Peninsula. The weather in the area is characterized by temperate summers and winters, significantly affected by the Chesapeake Bay and the Atlantic Ocean. The soil is sandy and deep.As of 2014, Virginia Wine lists 2 commercial wineries in this AVA, Bloxom Vineyard and Chatham Vineyard on Church Creek. Between them, they produce dry and sweet and red and white wines.

The hardiness zone is 8a.

Languages

This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.