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, let's look at the most often asked gardening question "Why doesn't my lemon fruit?"

The answer is that "lemons are very sensitive to cold, frost, extreme heat, bad drainage and air pollution" (source: 'The Australian Fruit and Vegetable Garden' by Clive Blazey).

All of those problems can be avoided if climate needs are accurately described on nursery plants, so that the correct variety is selected for the particular climate. To help with this, Diggers have...

Cold Zones (CZ)

Lemons don't like frost (CZ 8-9, i.e. inland), but thrive in all capital cities and coastal areas, which are frost free (CZ 10-11).

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 CZ 7-9b. However custard apples won't fruit in areas of frost, and so must be planted in CZ 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.

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Heat Zones (HZ)

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

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

The only part of Australia that most resembles the English climate is Tasmania (HZ 1-2, 7 days over 30°C). Brisbane and Perth have 8 times as many 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 does best in Heat Zones 1-4 (i.e. 1-30 days over 30°C). So Brisbane, Adelaide and Perth (HZ 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.

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Growing Zones

Use this map to find your ‘Growing Zone’.

Based on the number of weeks that have days above 15°C we have four main zones across Australia, the Cool, Warm and Hot Zones, plus the Humid Zone which accounts for summer rainfall and the influence this has on seasonal sowing times.

When you locate which Growing Zone you are in, visit our Seeds to Sow Now page for a list of seeds suitable for planting in your area right now.

Click below for a full-sized map to help you locate your growing area.

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Cold Zones Of Major Areas

Cold Zones 8, 9a, and 9b (temperate)

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

Cold Zone 10 (sub-tropical)

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

Cold Zones 11 & 12 (tropical)

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

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