The oddities of the Micro-climate

One of my students asked me, the other day, what exactly was meant by the term "micro-climate".

It's a good question: this is a phrase which crops up in all the gardening books and articles, and yet it's rarely explained.

We all know what climate is, even though it's very hard to define it exactly: "errr, it means the outdoor conditions which occur where we live, and which vary from season to season but which are more or less predictable".

Here in the UK, for example, our climate is temperate, which means "not too cold (we get occasional freezing weather for a week or two, but we don't have permafrost and regularly get snowed in for weeks), not too hot (we have the occasional "phew, what a scorcher" but we don't live in a barren desert with nothing but sand dunes), pretty wet (but we don't get monsoons that sweep away the soil), but sometimes very dry (again, not deserts, though)."  Although that description is verging towards "weather" rather than "climate".

And if you are not sure of the difference -  "Climate is, but weather might be".

So, if it's raining one day, and sunny the next, that's the weather: but overall, we have a climate which is generally fairly stable and predictable: it gets colder in winter, it gets hotter in summer.

Within our own gardens, we all know that the north-facing side is going to be shady, damper, and colder than elsewhere in the garden. The south-facing side is going to get a lot more sun - so having a south-facing garden is often seen as a benefit when selling a house. East-facing gets the morning sun, and west-facing gets the evening sun.

So we all understand how the "climate" within our gardens varies according to things like which way it faces.

So what's a micro-climate, then?

Answer, it's the same type of variability, but on a very much smaller scale.

For instance, here's a lovely example: in one of "my" gardens, we have a wooden arch with climbers, at the base of each side we have an edged raised planter, containing a climbing rose. As these beds are a bit bare in winter, we moved a load of winter-flowering cyclamen from elsewhere in the garden. 

The situation, or location, would appear to be identical: the arch and the planters were built at the same time, using the same materials, the same soil to fill the boxes: two matching roses were planted.

The cyclamen came from the other side of the garden: a huge clump of them, somewhat overshadowed by other planting, and which we agreed would be just the thing for the planters. 

I divided them roughly into half, and planted up the two boxes: again, same soil, same plants, same time of year, same growing conditions, both equally watered.

So the cyclamen should flower equally well, shouldn't they?

And yet.... here's the right-hand one:

...and here's the left-hand one.

Quite a difference, as you can see!

One is flowering like a trooper, but the other, while making a good showing of leaves, had only a few flowers.

And the reason for this is micro-climate.

There are subtle differences between the two planters, even though they are only the width of the arch apart.

One is closer to the side fence, so it's just a little bit shadier.

One is more sheltered than the other: the presence of an outhouse to the left creates a wind-tunnel, so the less-sheltered one will be very slightly drier than the other.

One is surrounded by grass, one has a narrow paved path in front of it: so rain will tend to run off the paving and into the bed on that side, rather then being absorbed straight down, as it were, into the grass. This means that one planter will get slightly more rain than the other.

And so it goes: there are many small differences of this type, all of which add up to different micro-climates in areas which may be situated quite close together, yet where plants show differing rates of success. 

This isn't a problem, as such: in fact, the presence of micro-climates means that we can nearly always find "just the right place" for a particular plant; if a plant isn't doing well, dig it up and plant it elsewhere in the garden, until you find that spot where it flourishes.

As lovely Mr Bob Flowerdew used to say: "If a plant isn't doin' well, give it a roide in the wheelbarrer/"  

Or, to put it another way - find it the micro-climate that it needs!

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