Changes

An alternative system for describing plant hardiness is to use indicator plants (the USDA also publishes a list of these to go with their map). Common plants with known limits to their range are used. For example, many people will know whether lemons will grow in their locality. If you then say Geraldton Wax will grow more or less where lemons will grow you have defined the range of Geraldton Wax with some accuracy (whether or not it will flower is another problem). Unfortunately no two plant species have exactly the same requirements and there are even within-species differences. 'Meyer' lemons, for example, are more cold tolerant than 'Eureka'. You can really only define core areas and they are often fairly arbitrary.

An alternative system for describing plant hardiness is to use indicator plants (the USDA also publishes a list of these to go with their map). Common plants with known limits to their range are used. For example, many people will know whether lemons will grow in their locality. If you then say Geraldton Wax will grow more or less where lemons will grow you have defined the range of Geraldton Wax with some accuracy (whether or not it will flower is another problem). Unfortunately no two plant species have exactly the same requirements and there are even within-species differences. 'Meyer' lemons, for example, are more cold tolerant than 'Eureka'. You can really only define core areas and they are often fairly arbitrary.

==United Kingdom and Ireland Hardiness Zones==

 

===United Kingdom and Ireland Hardiness Zones===

[[Image:UK zonemap.png|thumb|UK hardiness zones]]

[[Image:UK zonemap.png|thumb|UK hardiness zones]]

Due to the moderating effect of the [[Gulf Stream]] on the [[Ireland|Irish]] and [[United Kingdom|UK]]'s [[temperate]] [[maritime climate]], the UK, and Ireland even more so, have rather milder winters than their northerly position suggests.

Due to the moderating effect of the [[Gulf Stream]] on the [[Ireland|Irish]] and [[United Kingdom|UK]]'s [[temperate]] [[maritime climate]], the UK, and Ireland even more so, have rather milder winters than their northerly position suggests.

The 1990 map shows 10 different zones, each of which represents an area of winter hardiness for the plants of agriculture and our natural landscape.  This was revised to introduce zone 11, representing areas that have average annual minimum temperatures above 40°F (4.4°C) and that are therefore essentially frost-free.

The 1990 map shows 10 different zones, each of which represents an area of winter hardiness for the plants of agriculture and our natural landscape.  This was revised to introduce zone 11, representing areas that have average annual minimum temperatures above 40°F (4.4°C) and that are therefore essentially frost-free.

===Updates===

===Updates===

There are problems with this 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), 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, Mt. 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 can choose 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. There may even be a case for publishing a list of weather stations and their zone classification to allow best use of local conditions.

There are problems with this 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), 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, Mt. 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 can choose 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. There may even be a case for publishing a list of weather stations and their zone classification to allow best use of local conditions.

==See also==

==See also==