Context and disclaimer
While the concept of microclimates is applicable to all climates and species on earth, the purpose of this article is to consider microclimates in terms of the urban and (particularly) suburban environment and regarding the growing off productive species in those areas.
Disclaimer – I am old. I also tend to be pretty analogue in my thinking, so while I do suggest websites and aps which will help to make sense of your microclimates I also talk about stuff you can do from scratch without the need for extensive digital skills. You have been warned!
What is a microclimate?
Definitions
Below are a selection of definitions of the term ‘microclimate’ from various sources -
Wikipedia - A microclimate (or micro-climate) is a local set of atmospheric conditions that differ from those in the surrounding areas, often with a slight difference but sometimes with a substantial one. The term may refer to areas as small as a few square meters or square feet (for example a garden bed or a cave) or as large as many square kilometres or square miles.
Dictionary.Com - the climate of a small area, as of confined spaces such as caves or houses (cryptoclimate ), of plant communities, wooded areas, etc. (phytoclimate ), or of urban communities, which may be different from that in the general region.
Merriam-Webster - the essentially uniform local climate of a usually small site or habitat
So from the above definitions, it can be seen that a microclimate is a small area which has a different climate from the prevailing one in the area (macroclimate). For us that meant areas within our yard which were different from the cold and heat that is western Sydney. As usual with these things, the concept is simple but there are various factors which may play out separately, or together and can result in a variety of microclimates in any given area. These factors are -
Temperature – The temperature of a microclimate may be affected in many different ways, including warmer winter temperatures caused by the presence of thermal mass such as buildings of brick, clay or stone; large rocks and/or bodies of water such as pools, ponds or streams, or full water tanks. A glasshouse will also result in a warmer temperature inside the structure. Conversely, the temperature of an area may be reduced in summer by surrounding trees or bushes sheltering an area from the hot summer sun and wind or bodies of water.
The northern side of a shed can provide a warmer, protected microclimate for winter growing
Light – All plants need light but not all plants need full sun. The amount of light available in an area will be moderated by the presence of shade from buildings, sheds and fences (Full shade) and/or surrounding foliage from trees and bushes (which may be partial or dappled shade, depending on foliage density). Deciduous plants will provide foliage cover in the warmer parts of the year and then lose their leaves to allow extra light in during the winter. The amount of visible light from the sun is also tied to the amount of infrared light (heat) from the sun so increasing light levels will also have an impact on the temperature of a microclimate as well. The time of year will also have an impact on sun/shade due to the angle of the sun in the sky.
Air Circulation – in this case wind, which can be hot or cold, warm or cool. Cold winds can be very hard on temperate crops, and hot winds can dry out just about anything rapidly. This will be modified by surrounding foliage including trees and bushes, and structures like houses, sheds and fences.
Water – There are a number of ways in which water will impact the microclimate of an area. Soil moisture/drainage have considerable impact on what you can grow and how easily it can be grown. The books always tell you that the best soil is “moist but well drained” but I would bet that most of us a closer to one of the extremes than the ideal. A sandy soil will tend to be drier than a clay soil, which may contain moisture to the point of causing root rot in fruit trees.. Humidity due to bodies of water in the area can be good, reducing the amount of irrigation needed for your fruit and veg, but if coupled with low air circulation it can mean fungal problems may occur.
Also, water coming off unplumbed roofs such as sheds, garages, chicken coops or whatever on your land or that of your neighbour and impervious areas such as driveways, footpaths or other paved areas will result in localised areas staying damper for longer than the surrounding areas.
Why is it important to understand microclimates?
So, why is it important to understand microclimates in general and then be able to apply this knowledge to your own property?
A knowledge and understanding of microclimate is key to successful growing of productive crops (food, fibre, biodiversity and/or amenity) in small suburban and urban areas, because -
1. It can enable you to pick which areas of your property will be unsuitable for a particular plant or class of plants. Moisture loving plants being put into a dry microclimate will not thrive and be productive.
Water runoff from sheds and tank outlets can result in a damp microclimate
2. Conversely. If the microclimates on a property are identified and made use of, they can ensure that plants are placed where they are most likely to survive and thrive, for example by planting a bog plant into that area of the yard that always seems damp.
3. Microclimates can be modified or created so Identification and study of existing microclimates will enable modification of them to better support the growing of desired productive plants or the creation of entirely new ones that better suit the types of productive plants to be grown.
Part 2: Identifying Your Microclimates
