Hortiforum

From the beginner gardener just starting their orchard to the experienced grower looking to merely fill a gap in an established garden, everyone should consider the climatic preferences of different plants. These preferences are most commonly shown on maps that illustrate various climate zones, which may be called ‘climate maps’.

Climate maps are commonly presented either as broad biome classifications, such as Tropical, Arid or Temperate, or through more specific data like hardiness zones, heat zones or cold zones. These tools can be very useful in helping gardeners identify plants best suited to their local climate, given the most important factors in determining plant suitability includes average and minimum temperatures, as these are largely outside a gardener’s control without significant intervention. That said, certain classifications, such as the Arid zone, group together regions with vastly different temperatures, based solely on low rainfall, rather than temperature similarity.

• Climate zone 1 – high humidity summer, warm winter
• Climate zone 2 – warm humid summer, mild winter
• Climate zone 3 – hot dry summer, warm winter
• Climate zone 4 – hot dry summer, cool winter
• Climate zone 5 – warm temperate
• Climate zone 6 – mild temperate
• Climate zone 7 – cool temperate
• Climate zone 8 – alpine

Preferred Climates: A plant’s preferred climate is the zone where conditions are ideal for vigorous growth, good productivity, high-quality fruit, and long-term health. This usually corresponds to the plant’s native environment or to a climate that closely resembles it. For beginner gardeners, choosing plants that suit the local climate gives the best chance of success, as this meets one of the most important requirements for plant health.

Marginal Climates: A marginal climate is one where there is a distinct possibility of failure. A plant may survive in some areas of the zone, but potentially with reduced yield, lower fruit quality, or a greater risk of pests, disease or damage from extreme conditions. In some cases, the plant may not fruit at all. For example, Guavas grown in Melbourne may ripen during the cooler months, which can lead to poor-quality fruit and lower yields.

Although these climate maps are based on data and not determined arbitrarily, they do have limitations. For this reason, they should be seen as general guides rather than strict rules. Local factors, particularly microclimates, can have a significant impact on plant suitability. Elements like slope orientation, elevation, proximity to bodies of water, and the surrounding landscape, including forests, farmland or urban development, can all influence local growing conditions. For example, large bodies of water such as lakes or the ocean often moderate local temperatures, which can make an area more suitable for tropical or subtropical plants. On the other hand, a south-facing slope at higher elevation may be considerably cooler than a north-facing slope at lower elevation, even within the same region. Beyond temperature, soil type and rainfall are also important, especially for gardeners who prefer not to rely heavily on soil improvement or irrigation.

For example, gardeners in Sydney know from experience and observation that Mango trees can grow successfully in Sydney, including the western suburbs where light frosts occur. This is despite Sydney being classified as a warm temperate climate rather than a tropical or subtropical one (being the preferred climates for Mangoes). In this case, saying that Mangoes are unsuitable for warm temperate areas can be misleading. However, that same advice may be more accurate for gardeners in Melbourne. Although also considered warm temperate, Melbourne experiences noticeably cooler conditions. Mango trees may still grow there, but they often need extra protection and care, and they may not fruit reliably. Banana plants are another example. They can be grown in both Melbourne and Sydney, but in more inland regions that experience heavier frosts, they may not survive, even if those areas have warmer summers.

Refer to Climate Unfussed for a selection of plants which are adaptable to a range of climate zones.

A gardener can improve the chances of success in a marginal climate by providing plants with optimal conditions in the following areas:

• Cold Tolerance
• Salt and Wind Tolerance
• Preferred Soil
• Soil PH
• Rainfall
• Pollination