A microclimate may be defined (at least according to 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."
I find it fascinating that the variation in microclimate, even within as small area can make quite a difference to what you can grow, or how what you are growing responds.
Take this for example:
At the end of our street we have a reserve which goes down towards the shops, allowing us to be able to walk there in a few minutes. It runs east to west and is about 350metres long. The width varies from 33metres to 41 metres and the reserve is bordered by house back or side fences all the way down. When we first moved in, the local kids would construct dirt ramps and use them to jump their bikes over, and within the family we still refer to the area as ‘the jumps’.
Western end, looking east
There are a few old and quite large gum trees and growing down their and recently the council planted a series of natives down the asphalt walking path. About ten years ago the council planted, along the full length of the fences on each side of the reserve a whole stack of Japanese Photinia shrubs (photinia seratifolia) and when walking down the shops it was these plants that fascinated me.
Eastern end, looking west
Due to the east/west aspect of the reserve, the photinia on the northern side is in the lee of the border fences, whereas the photinia on the southern side is exposed to the western Sydney sun for pretty much the whole day. The differences between the two sides have been exacerbated recently because we have not had decent rain in months!
While there is some variation on both sides of the reserve, in general terms, this is what they look like.
The northern side
The photinia a comparatively tall with an average between 3.5 metres to 4 metres and are very bushy. There are a couple of stands that have been trimmed back by residents, but even allowing for that they are still quite bushy. The undergrowth is also green and lush with plants like sedge that tend to indicate that the soil is still quite moist. The grass leading up to the bushes is also lush and green, out to a distance of up to six metres from the fence line.
The Southern Side
The photinia is generally shorter and scrappier with an average height of 2.5 metres to 3 metres and nowhere near as bushy as the photinia on the northern side. Also, there are some areas where the photinia appears to be drying off and dying. The undergrowth is much lower, more dried out and almost completely lacking in some areas. The grass itself is brown and dry leading all the way up to the border fences.
Conclusion
These plants were put in at the same time, have received the same degree of care (or lack of it) and basically exist within 30 to 40 metres of each other. So, it seems that the difference is entirely due to the microclimate resulting from being on the lee side or sunward side of the fences.
Photinia are not a ‘productive’ species in any way, but it would be interesting to find out the impact of this sort of microclimate difference on fruit or nut trees, edible leaf growing trees like the curry tree or bay tree or native shrubs and trees.
If it had been me, I would have thought that the shading from the northern fence and full sun on the southern side would have meant the effects were reversed and this has been an interesting lesson for me. I hope others find this interesting and useful too.
More about microclimates can be found here
