Gardening - Keeping your cool

By: Andrew Steens

With this year’s rather active La Niña weather system and global warming adding an extra push to temperatures, this summer is shaping up to be hot and sticky. For tropical plant aficionados like me, hot and humid weather with regular rainfall is a recipe for success. Previously marginal plants such as sugarcane, heliconia, pawpaw, jackfruit, mango and bananas will thrive. However, the gardener may suffer. With northern European ancestry and carrying an extra kilo or twenty, I tend to melt in these conditions.

There are several tips and techniques that gardeners can use to improve conditions for both working and relaxing around the property. Firstly, save up your heavy work for the early morning or evening when it is cooler. Overcast days are a boon for the same reason. Of course, wear a good sunhat and loose-fitting clothing through the heat of the day and drink plenty of water.

Shade is critical. How much of your property is covered in shady trees? Not only do shade trees provide direct cooling by cutting out sunlight, they also reduce temperatures by virtue of transpiration, which cools the surrounding air as the trees pull water up from the root and release it as water vapour from the leaves. The shade also reduces the “heat island” effect, where sunlight is absorbed by buildings and paving, being released back to the atmosphere as heat.

Although any trees will provide these free and essential services, my preference is for small leaved deciduous trees on suburban properties. Small leaves allow filtered light through, which is better for the plants or lawn below and, come autumn, the smaller leaves are less messy than large leaved varieties. Deciduous trees also allow maximum light onto the property over winter when every bit of sunlight is appreciated.

In our area, excellent small-leaved deciduous specimens that love the heat include albizzia julibrissin (silk tree), jacaranda mimosifolia, schizolobium parahybum (Brazilian fern tree), lagerstroemia indica (crepe myrtle), melia azedarach (Indian bead tree), gleditsia ‘sunburst’ (golden honey locust), robinia varieties (e.g. mop top), radermachera sinica (canton lace) and my current favourite tabebuia chrysantha (golden trumpet tree), which flowered for the first time for me this spring.

Water is the other natural solution to excess heat. A swimming pool is ideal for a cooling dip in the heat of the day after mowing the lawn or digging the veggie garden. Even a little pool is worthwhile for this. I recall using a recycled spa pool as a cold plunge pool for summer; easy to tuck away out of sight in the garden and not too much water needed to fill it.

Not to be overlooked, though, is the cooling effect of water features in the garden. Just the sight of water, such as a trough with waterlilies or a reflecting pond, has a psychological effect. Add the sound of trickling or running water and the effect is increased. Place small water features near your outdoor living area, and you will benefit from these small gains.

If you have sufficient water, then spraying hard surfaces, such as pavement, can reduce nearby air temperatures by several degrees. Moving water is even more effective. A spray-style fountain can decrease surrounding air temperatures in a radius of several or even tens of metres. In times of high heat stress, consider turning on your sprinklers. It’s not the ideal time to water the garden, but the plants will love you for it, as will your family!

Andrew Steens


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