Microclimates are one of the biggest factors affecting our success with growing healthy plants. Every garden is totally unique. We have to play ‘detective’ to discover clues in different zones to fully understand the opportunities and challenges. Let’s dig deeper into what kinds of microclimates might be in your garden and how to use them to your advantage.
What is a Microclimate?
A microclimate is a suite of very localised conditions that differ from those in the surrounding areas. Often just slightly but sometimes considerably! Think of a microclimate as a miniature climate. It may be less than a metre or few feet in size or a substantially larger area in your garden! Microclimates may occur naturally, or you can intentionally change the conditions to suit your needs.
What Aspects Affect Microclimates in your Garden?
There are a variety of factors that influence microclimates in our gardens. These include:
- Air and soil temperature. These conditions affect seed germination and plant growth.
- Solar radiation and sunlight angles during the year affect daylength and shade.
- Wind speed and direction can provide cooling breezes or hot dry and damaging gusts.
- Humidity (high vs low).
- Soil type, moisture-holding capacity, pH, drainage and structural properties.
- Rainfall and moisture.
- Vegetation and maturity of established species. A new house block with no plants will have a very different microclimate to when mature shrubs and trees are growing.
- Directional aspect the garden area faces (N, S, E or W).
- Slope, elevation and topography (affect temperatures, frosts and water movement). e.g. A low level property in a valley may have lower temperatures as cold air sinks. Gardens may get frost and have more moisture from run-off. Whereas a property on a hill may be cooler and have drier soil.
- Air circulation (well-ventilated areas are cooler).
- Thermal properties of building surfaces and nearby structures like walls or fences. For example, most glass reflects some heat but does absorb a small amount and diffuses a lot of direct solar radiation. Bricks and concrete absorb and store heat on warm days and release it overnight creating a warm microclimate in the immediate area. Some hard surfaces like a path, paving or driveway may radiate extra heat.
- Surrounding buildings in cities and densely populated areas can also be impacted by the urban heat island effect.
No Two Garden Microclimates are the Same
These various dynamics can create comfortable, favourable growing conditions or especially challenging ones! It’s worth playing detective to investigate the microclimates in your garden. Not all of those factors may influence the conditions in your garden. But at least some of them will.
I live in a subtropical climate in SE Queensland, Australia. However, even within our local region and suburb, the microclimates are very different. Based on regular feedback from my neighbours who are also keen gardeners, the prevailing winds, rainfall and sunlight exposure varies widely from one side of our street to the other! It can be wildly windy on one side of the street and peacefully calm on the other. We even experience different rainfall depending on which way the wind is blowing! We often compare our data and although we live in the same street just metres apart, our aspect, soils and rainfall vary considerably.
Depending on the aspect your garden faces, you may encounter a wide variety of microclimate conditions. e.g. harsh sunlight or full shade, strong prevailing winds and damaging storms or cooling breezes that bring relief on hot days.