The heat is on


    By John Weldon

    I love the way a brick wall soaks up heat, holding it fast all day, then radiating it out into the air as the evening cools. Many plants love this too, basking in an electric blanket-like microclimate that allows them to grow faster and bigger, especially early on in spring when they need that extra boost. So much the better if the wall is north facing, as it will be in the sun all day, shade trees and or other structures permitting.

    Tomatoes love this northern aspect, as do many natives such as westringia, some banksias and lomandras, and plants that thrive in drier more arid climates, such as agave, bird of paradise, olives, lemons, rosemary, thyme and lavender. Frangipanis, too, love a toasty north-facing wall.

    The direction your garden faces, the shade-throwing structures around it and the microclimates these create are crucial considerations for Melbourne gardeners, when working out what to plant where. Lemons, for instance, need eight hours of sun a day to thrive. Will that sunny north-facing spot you’ve chosen for your Meyer, still be so in winter when the sun rides lower in the sky and the shadows stretch longer and deeper? If not, it might struggle or expire.

    Although north-facing spots see the Sun all day, they are not always the hottest of gardens. In Melbourne, that prize often falls to those that face west. In the height of summer, the hot afternoon sun will bake their soil and heat the air making for a searing, stifling atmosphere that can wither even the most dedicated sun-lovers. Friable soils will become crumbly and dry, clay-based soils like rock. Even the hardiest of plants will appreciate a little love when the mercury heads high. Mulch will shade the soil, keeping it cool, but only if it’s organic. Pebbles and gravel will act like a heat sink, heating the soil up even further and frying shallow roots. You might want to water more often too, especially newer plantings, but do so in the cool of the morning as otherwise the water will just evaporate and / or create a moist humid atmosphere around plants that can lead to the development of mould and fungus.

    When planning north or west facing gardens, it also pays to spend a little time noting where and for how long the sun hits the ground during the day, especially in urban areas where neighbouring structures can shade even the warmest parts of the garden all day. Alternatively, if there is no shade and all you have is a western or northerly aspect, you can engineer a microclimate more amenable to plants that do like a little shade by growing a deciduous vine, such as wisteria up a trellis. This will offer shade in summer and, when the leaves drop, will let light through in winter.

    This planning takes time, but it pays for itself in bigger crops, fewer trips to the nursery to replace struggling plants and trees, and the creation of microclimates that make the garden a better place to be for everyone. And that’s always a good thing. 

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