If there was ever a week for lounging in the garden, the one following Christmas is surely it. Now is the time for putting your secateurs down and your feet up. It's the season for basking in what you have already done and enjoying your plants as they are. But it can be hard to rest on your laurels without shade. The languorous thrill of doing nothing loses its appeal in baking sun.
Shade has always been an essential landscaping ingredient. In ancient paradise gardens, the canopy of cedars transformed parched Mesopotamia into luxuriant abundance. Records of a pocket garden in Thebes circa 2009-1998BC show sycamore figs filtering sunlight to create a cool Egyptian oasis. Italians have long understood the power of a grape-vine-covered pergola to counteract the effects of intense heat, while the English have sheltered under oaks and elms, and the Japanese have sought the play of shadows cast by maples, pines and cherry blossoms.
Trees can lower the temperature by up to 12 degrees.Credit:Kirk Gilmour
Plants cast cooler shade than man-made structures thanks to the fact that they release water vapour. In absorbing water from the soil and then evaporating it into the atmosphere, plants lower the temperature of their immediate surrounds. This is why irrigated open spaces have been found to be cooler than built-up, vegetation-free urban ones.
At a recent panel discussion at the Royal Botanic Garden Melbourne, Diggers Club founder Clive Blazey described how a large Desert Ash (Fraxinus angustifolia subsp oxycarpa) in the Heronswood garden in Dromana lowered the temperate beneath its canopy by as much as 12°C. Moreover, he said, 400 people could fit beneath it.
Sitting under a shady tree offers a post-Christmas respite.
But Desert Ashes aren't for everybody and selecting a plant to provide respite on a hot day is often a question of aesthetics. Take the eucalypt, for example. While Blazey says he finds gum trees have too much of an "arid association" to create the "lush, cooling environment" he wants in a garden, horticulturalist Millie Ross likes the "beautiful shadows" they cast. Dean Nicolle, of South Australia's Currency Creek Arboretum, mentions E. leucoxylon, E. petiolaris and Corymbia maculata as eucalypts that provide good shade.
Horticulturalist and author Stephen Ryan has described the golden-leafed form of the Indian Bean Tree (Catalpa bignonioides "Aurea") as a "most impressive shade tree", with spreading limbs and large foliage. Being too big for the average garden, it is often coppiced, making it more of a shade-giving shrub instead.
With careful shaping many trees – everything from apricots to zelkovas – can be used to cast shade. But whatever you choose, placement is critical to maximise sun protection. Deciduous plants have the advantage of becoming open in winter and letting in sun when you most want it while climbers can lend an air of wildness.
Annual vines – beans, peas, small cucumbers, for example – can tower above you in months (though won't necessarily provide dense cover), while climbers such as wisteria, Chinese star jasmine, roses and pandoreas can take a little longer to engulf pergolas and arbors. Contrary to popular perception the terms pergola and arbor are not interchangeable, with arbors including the leafy avenues formed when trees are pruned into overhead arches.
For an even more formal interweaving of branches, there is pleaching, whereby trees – usually grown in a straight line – are tied together and clipped into a living ceiling. The technique, which was popular in France and Italy in the 17th and 18th centuries, has been enjoying a revival in recent years. A double row of plane trees pleached into a pergola made an appearance at last year's Melbourne International Flower and Garden Show.
Now is the time to watch where the sun falls and think about your options for next year.
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