The Diggers Club home page > Climate maps
 

Choosing the right plants for your climate

Ninety percent of gardening problems are caused by gardeners not understanding the climate needs of their plants. This is hardly surprising since the climate models (tropical, sub-tropical and temperate climates), particularly the popular Yates Garden Guide, are so simplistic as to be misleading.

For example, lets ask the most often asked gardening question- Why doesn't my lemon fruit? Answer - "lemons are very sensitive to cold, frost, extreme heat, bad drainage and air pollution," source: Diggers' Fruit and Vegetable Garden. All of those problems could be avoided if climate needs are accurately described on nursery plants so the correct variety is selected for the particular climate ie:

Cold

Lemons don't like frost (Cold zone 8-9),ie: inland, but thrive in all capital cities and coastal areas, which are frost free. (Cold zone 10-11) See cold zone map

Heat

Lemons need less heat to ripen than oranges -ie: minimum 30 days over 30°C, but not more than 90 days. (Heat zone 3-7) See heat zone map This excludes Hobart in zone 2, as well as Townsville and Darwin, but applies to all other capital cities.

Water

Lemons need seasonal watering, they are a two drip plant (water code drip drip). They like good drainage, not constantly moist soil (water code drip drip drip), and are not drought tolerant (water code drip).

Diggers climate guide

LemonsOranges
Cold zone 10-11(Meyer 9b) 9b,10,11
Heat zone 3-7 6-7
Water dripdrip dripdrip

Comparison to Yates Garden Guide

European and American garden experts discarded these guides 50 years ago, opting for Cold Hardiness climate zones in the 1960s, and Heat Zone guides in 1998.

"Citrus - do well in warm and mild climate, providing frosts are not severe."

The Digger's Club adapted these guides for Australian conditions in 1998, effectively providing the first accurate garden guide that allows Australians to understand the extremes of our climate.

One of the benefits of buying from us is that we are the only nursery in Australia that gives such precise information!


Cold zones explained

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Australia has a warmer climate than the countries of origin of most of our introduced plants. Tulips must have a period of frost to flower, and will only repeat flower in cold zones 7-9b. However custard apples won't fruit in areas of frost, and so must be planted in zones 10-13. Locate your garden's cold zone, which is described by its absolute minimum temperature, and choose appropriate plants. It will increase your gardening success.

Frost free
Zone 12 +10°C to +16°C
Zone 11 +4°C to +10°C
Zone 10 -1°C to +4°C
Frost
Zone 9b -4°C to -1°C
Zone 8-9a -12°C to -4°C

Towns in the temperate zones 8, 9a, and 9b:

Canberra, Kalgoorlie, Bendigo, Ballarat, Albury, Mildura, Griffith, Wagga, Bathurst, Orange, Dubbo, Adelaide Hills, Riverland, Riverina and Sunraysia.

Towns in subtropical zone 10:

Brisbane, Sydney, Melbourne, Adelaide, Albany, Bunbury, Mornington Peninsula, Geelong, Bega, Coffs Harbour, Byron Bay, and Sunshine Coast.

Towns in tropical zones 11 and 12:

Darwin, Cairns, Townsville, Broome, Mt Isa and Perth.


Heat zones explained

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Excessive heat is the major cause of plant failure in Australia. Some plants suffer physiological damage when the temperature rises above 30°C. This heat zone map indicates how many days over 30°C each region experiences. The map has 14 heat zones. Locate your garden's heat zone and only choose plants that suit your zone.

Blue poppy - HZ 1-4, CZ 7-9b
Yates Garden Guide - "Notoriously difficult to grow."

 

The only part of Australia that most resembles the English climate is Tasmania, heat zone 1-2, 7 days over 30°C. Brisbane and Perth have 8 times as many hot days (days over 30°C) and Melbourne has 5 times as many, which explains why many plants fail. For example, the exquisite blue poppy from Tibet has a heat zone code 1-4 (ie: 1-30 days over 30°C). So Brisbane, Adelaide and Perth (heat zones 4+) are too hot, as they have 45-60 days over 30°C. But Melbourne, which isn't too hot (CZ 4 in summer), is actually not cold enough in winter, because the poppy must have frosty winters to remain as a perennial. This need for frost eliminates Melbourne (HZ 10), so its recommended area is Tasmania and the dark blue areas of Victoria and N.S.W.


Growing weeks explained

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Our map shows the number of growing weeks (above 15°C) throughout Australia. Some annuals, like beefsteak tomatoes need 16 growing weeks to flower and fruit, which means that they will struggle when grown outdoors in Hobart, which only has 13 growing weeks. Zones are determined by how many growing weeks an area can expect. Locate your area on the map to help you choose seeds that will succeed within your growing weeks.