                    ************************************
                           PLANT HARDINESS ZONES
                    ------------------------------------
                      An explanatory note accompanying
                      Rel 2 of the FS2k Trees Library
                                    by
                               Gerrish Gray
                                 2000-12-14
                    ************************************

The trees in this FlightSim scenery library have mostly been classified by 
the 'Hardiness Zones' in which they occur.  

     IMPORTANT NOTE: This data is included only as a guide to the 
     selection of trees.  There is nothing compulsory about it and 
     designers are free to 'plant' trees from any band or hardiness
     zone in any part of the world (providing appropriate settings 
     are used in the design tool!).

A wide variety of factors affect the geographical range of different plant 
species, including temperature, rainfall, soil conditions etc.  One of the 
most significant is the minimum winter temperature that a species can 
withstand, and it has been found that plants can be loosely classified by 
this factor as a useful aid to identifying the species that will grow in 
any particular geographic location or climatic zone.  A number of 
authorities, including the US Department of Agriculture (USDA), have 
established 'plant hardiness' indices based on this idea and published 
maps showing minimum temperature zones in different parts of the world.

The most widely used index (and the one used for this library) identifies 
the following zones
===========================================================================
ZONE    MINIMUM ANNUAL TEMPERATURE    Climatic Zones /
  #      Farenheit        Celsius     Typical Locations (*)
----  --------------  --------------  -------------------------------------
  1      Below -50F     Below -45C  Arctic
  2   -40F to -50F  -40C to -45C  Sub Arctic, Yukon, Mongolia
  3   -30F to -40F  -34C to -40C  Calgary
  4   -20F to -30F  -29C to -34C  Montreal
  5   -10F to -20F  -23C to -29C  Chicago 
  6     0F to -10F  -18C to -23C  Kentucky, Switzerland
  7    10F to   0F  -12C to -18C  New York, Germany, Beijing
  8    20F to  10F   -7C to -12C  Oregon, Houston, Western Europe
  9    30F to  20F   -1C to  -7C  California, Southern Australia
 10    40F to  30F    4C to  -1C  Sub Tropical, Mexico, Hong Kong
 11        Over 40F        Over 4C  Tropical, Hawaii, North Australia   
---------------------------------------------------------------------------
   (*) Note the slightly surprising differences between the USA and Europe, 
       due to the 'harder' winters experienced in much of the continental 
       USA as opposed to relatively-temperate Western Europe
===========================================================================

A slightly refined version of this index is used for the USDA's Hardiness 
Zone Map for North America, which can be found on the internet at

        http://www.ars-grin.gov/ars/Beltsville/na/hardines.html

Hardiness Zone maps for other parts of the world (some of which use 
different temperature ranges) can be located on the internet by performing 
a search for 'plant hardiness'.  Sample maps are also included with this 
documentation.


Gerrish Gray
Dec 2000
mailto:gerrish.gray@wimborne-dorset.fsnet.co.uk
