Trees naturally cool things down

There have been days on end where there has either been one of our 11 banks of sprinklers running or staff members hanging on the end of hoses watering the plants.

This has gone on for 24 hours a day, but things have stood up well, and we have still been able to get other work done.

Well done, crew, it is a hard task keeping plants looking this good when they can only draw their moisture from such a limited source that a pot provides.

This extreme heat makes you think though of just how much plants cool our environment.

I think most of us have experienced walking into a shady fern gully on a hot day and felt the air temperature drop significantly.

Or visited a shady garden with a well-established tree canopy and good understorey planting to experience that same drop in temperature.

It is a more significant drop in temperature than if you walked into the shade of an umbrella, shade sail or the shadow of a building.

This is because trees actively cool their environment as well as provide shade, so much so that the shade from trees can be 10°C cooler than the shaded area under a man-made structure that can slowly heat up and radiate heat down into the shaded area below.

The surface temperature of walls, roofs, concrete, asphalt and paved areas shaded by trees can be reduced by more than 20°C.

This reduces the amount of heat absorbed and held in their thermal mass, which is released into the surrounding environment after the sun goes down.

Shade from trees does not just benefit the areas that the shade falls on directly, but rather it creates a cooler environment in the area surrounding it.

This is achieved through a process called evapotranspiration where trees absorb water through their roots and release it as water vapour into the air.

The process uses heat energy from the surrounding air to evaporate the water, which cools the leaves and the surrounding environment, similar to how we cool ourselves by sweating.

This cooling effect is the same principle that evaporative air conditioners work on, and it all happens without you having to turn it on or pay for the running costs.

In a garden, the cooling effect doesn’t end there, as the moisture-enriched air then drifts through the surrounding garden, creating a much more pleasant microclimate for other smaller plants and shrubs to grow and do the same on a smaller scale.

Trees also slow the wind speed down on windy days, helping you achieve a more stable temperature in and around your home.

The use of trees to shade and cool your house and garden can reduce your air conditioning needs by as much as 30 per cent, while enhancing your lifestyle by increasing your living space to include your outside areas on those hot summer days.

Creating a shady yard also offers you and your children an area to relax and play in, out of the way from the sun’s harmful UV rays. A mature tree can block up to 80 to 90 per cent of solar radiation with its canopy.

The microclimate created by trees also makes it easier to establish other plants in the garden, allowing for quicker results and a more diverse plant choice.

So, early consideration needs to be given to the placement and type of trees that are going to provide all these benefits as the garden matures.

We need to adjust the mindset that trees should not be taller than the house and that they should not overhang the house.

But we also have to keep in mind that we need to make the appropriate choice of tree for the position, as things can quickly go pear-shaped if the wrong choice is made.

Be sure to seek the advice from someone who knows the different characteristics and suitability of trees to be used among built structures and that they fully understand the size and constraints of the site.

In the hot climate that we live in, it is hard to understand why more importance is not given to establishing a much higher percentage of tree canopy coverage of our home gardens, streetscapes and public spaces.

It would make our lovely area we live in so much more liveable, increase property values, reduce our heating and cooling costs and beautify the place even more all at the same time.

So next time the temperature starts to near the high 30s, take a stroll through a shady garden to see how much difference trees make and then let’s see if we can encourage people to plant more trees so we can all reap the rewards.