Plants of the world - Principles of Horticulture - page 19

World climatic zones
Seven major climatic zones found around the world
that have provided some useful garden and green
house species are as follows:
X Polar - very cold and dry all year, e.g. Greenland.
Example British garden species - arctic poppy
( Papaver nudicaule ).
X Temperate - mild summers and cold winters, e.g.
Britain and Ireland. Example British garden species
- clustered bellfl ower ( Campanula glomerata ).
X Arid - dry, hot all year, e.g. Northern Africa.
Example British garden species - many coloured
spurge ( Euphorbia polychroma ).
X Equatorial (tropical) - hot and wet all year, e.g.
Amazonian South America. Example British garden
species - sweet tobacco ( Nicotiana alata ).
X Subtropical - hot, humid summers and generally
mild to cool winters, e.g. south east China and
south east USA. Example British garden species -
African lily ( Agapanthus ).
X Mediterranean - dry hot summers and mild
winters, e.g. around the Mediterranean. Example
British garden species - sweet pea ( Lathyrus
odoratus ).
X Alpine - very cold all year in mountainous areas,
e.g. European Alps. Example British garden
species - alpine pink (Dianthus alpinus ).

2

Figure 2.7 Sweet pea originates in the Mediterranean
area

Climate in large countries

It should be emphasized that large countries such
as China, USA and Brazil (that have historically
been sources of many plant species for worldwide
distribution) may have several different climatic
zones within their border. Ecologically, these climatic
zones will relate to different biomes , with their
distinctive groupings of plants and animals (see
p. 37).
These different plant species originating in a single
country, but from different zones, may also have
different requirements for growing in Britain and
Ireland, reflected in their Royal Horticultural Society
(RHS) hardiness rating (see p. 21).
For example:
X China encompasses tropical, temperate and
alpine zones. Snake bark maple ( Acer davidii ) has
a RHS hardiness index of H5, while star-jasmine
( Trachelospermum jasminoides ) is rated H4.
X USA encompasses polar, temperate, alpine
and tropical zones. Creeping juniper ( Juniperus
horizontalis ) is rated H7, while blue blossom
( Ceanothus thyrsifl orus ) is given an H4 rating.

Figure 2.8 Creeping juniper originates in the USA

X Brazil encompasses tropical (wet, moist and dry
zones) and also a temperate zone in the south.
Blue passion-l ower ( (Passifl ora caerula ) is rated H4,
while paper fl ower ( Bougainvillea glabra ) has a H1c
rating .