SppDb, the companion plant database application to gCADPlus allows individual species to be classified in a ‘Zone’ field.
The figure below shows an entry for Acacia baileyana in the SppDb window.
SppDb is highly customizable. Here various terms have been used for zones and countries often have their own climatic zone descriptions. In the UK, for example, the RHS hardiness rating is often used, which has just 4 zones although they are sometimes used in combination:
H1 – Frost Tender, minimum 5 C, requires heated glass
H2 – Half Hardy, minimum 0 C, requires unheated glass
H3 – Frost Hardy, minimum -5 C, hardy outside in some regions or particular situations or which, while usually grown outside in summer, needs frost-free protection in winter
H4 – Fully Hardy, minimum -15 C, hardy throughout the British Isles
These might well be added if designing in the UK.
How to manage the addition of data about the suitability of species for particular climatic zones in SppDb. We show how to edit data and export a plant database file suitable for use in landscape design software such as gCADPlus.
Hardiness Zone
There are a number of other zone systems or hardiness classifications in use, some of which are quite specific to certain global areas. However, the USDA system is widely understood and probably the most comprehensive.
Used to indicate a plant’s tolerance to different climates and temperatures. Hardiness Zones are based on those defined by the United States Department of Agriculture, who has issued a map of North America showing areas where the normal minimum temperatures reached in winter are within a certain range. The latest revision was in 1990 and now uses 11 zones, the new zone 11 being frost-free with a minimum temperature of 4.4 degrees centigrade. For the sake of simplicity, Plant Base does not use sub-divisions (a, b & c) of the major zones.
USDA Zones
The USDA Zone definitions are as follows:
| Zone 1 | Below -45.6 C ( -50 F ) |
| Zone 2 | -45.6 to -40 C ( -50 to -40 F ) |
| Zone 3 | -40 to -34.5 C ( -40 to -30 F ) |
| Zone 4 | -43.5 to -28.9 C ( -30 to -20 F ) |
| Zone 5 | -28.9 to -23.3 C ( -20 to -10 F ) |
| Zone 6 | -23.3 to -17.8 C ( -10 to 0 F ) |
| Zone 7 | -17.8 to -12.3 C ( 0 to 10 F) |
| Zone 8 | -12.3 to -6.6 C ( 10 to 20 F ) |
| Zone 9 | -6.6 to -1.1 C ( 20 to 30 F ) |
| Zone 10 | -1.1 to 4.4 C ( 30 to 40 F ) |
| Zone 11 | Above 4.4C ( 40 F ) |
UK Zones
Only three zones are encountered in the British Isles, Zone 7 covers the eastern Scottish Highlands, Zone 8 includes most of Britain and Ireland except for the western coastal areas which are Zone 9.
In UK publications, the RHS hardiness rating is often used, which has just 4 zones although they are sometimes used in combination:
H1 – Frost Tender, minimum 5 C, requires heated glass
H2 – Half Hardy, minimum 0 C, requires unheated glass
H3 – Frost Hardy, minimum -5 C, hardy outside in some regions or particular situations or which, while usually grown outside in summer, needs frost-free protection in winter
H4 – Fully Hardy, minimum -15 C, hardy throughout the British Isles
Intermediate ratings are shown as H1-2, H2-3 and H3-4, while H1+3 indicates requires heated glass but may be grown outside in summer. Approximate equivalents to the USDA Zones are:
H1 = Zone 11
H2 = Zone 10
H3 = Zone 9
H4 = Zones 7 and 8
Europe