You don’t need me to remind you that’s it’s dry at the moment, so instead, I want to use this week’s Secret Garden to draw your attention to the flipside of any drought: water. Tomorrow marks the start of National Water Week. According to the organisers, it’s “the only nationally-focussed event designed to assist our community to take actions that help protect and conserve our most precious resource”. Sounds like a worthy idea to me, so to kick things off in our part of the world, I thought it might be instructive to actually sit down and think about what we’ve learnt about gardening during the last decade of drought.
1. We live in a boom and bust climate.
Everything we once considered normal with regard to our climate is now coming under review. I’m not a climatologist, but as a keen weather watcher, my theory is that our new reality is one of regular booms and busts. Where we once might have had a succession of dry years, followed by a succession of wet years, the Downs climate now appears to be even more extreme. Good rainfall events still occur, but these are regularly followed by one to three months of very dry conditions.
Garden making in this kind of boom and bust climate is all about being prudent. Install the biggest rainwater tank you can. That way, you can harvest plenty of rainfall when it’s wet, and eek the stored water out over a long period of time when it’s dry. My aim is to never see water running from the overflow outlet of my tanks.
2. Wind is the enemy.
Drought and heat make a formidable partnership. But the real nail in the coffin of any lush garden is wind – a hot north-westerly will dry out plant foliage quicker than washing on the line. One of the best tools in the waterwise gardener’s arsenal is the windbreak. Any semi-permeable barrier will do the job, whether it’s a tough plant species, shadecloth, bamboo panelling, even a picket fence. Slow down the wind, and you’ll dramatically reduce transpiration. Reduce transpiration, and you’ll give your garden the best chance to deal with prolonged periods of dry weather.
3. Shade is your friend.
Because so much of our gardening culture comes from northern Europe, where the sun is less intense and cloud is so common, we antipodeans tend to be terrified of creating too much shade. This is where we have to throw out the old rule book, and write a new set of rules applicable to our climate. In southern Queensland, sunlight is intense. Clear days overwhelmingly outnumber cloudy days. If we’re to live and garden wisely, we must embrace shade.
This doesn’t mean we all need to rush out and buy a Moreton Bay Fig to use a shade tree. On larger properties one may indeed make a magnificent place to hang a hammock, but for the average suburban block, tall shrubs and small trees planted on the western side of the house will help cool the atmosphere and reduce moisture loss from soil and leaves.
4. Mulch, but not too heavily.
The old pre-drought rule of thumb when mulching was to layer your material to a depth of 10cm. The theory went that mulch of a sufficient depth would stop weeds germinating and help retain moisture in the soil. During the drought, we’ve learnt that if you mulch too thickly moisture has trouble actually penetrating the mulch layer, unless the rainfall is very heavy, or the mulching material very coarse. For light showers to get down to soil level, a five centimetre layer of mulch is now recommended. This is adequate enough to stop weeds, but it is also thin enough to reap the benefit of lighter showers that might arrive between major rain events.
5. Take a triage approach to water use.
Assuming you have stored rainwater available for use in the garden, a helpful way to ensure you make best use of the water is to adopt a triage approach to irrigation. In medical terms, triage is the process of prioritising patients according to the severity of their condition. In horticultural terms, a process of triage can be used to prioritise the water needs of different plants, and deliver water according to need.
In my garden, the most drought sensitive plants are those in the vegie patch, and because growing our own food isn’t just a lark, the vegies get first dibs on any available water. Next come the fruit trees according to their individual needs, then the ornamental plants that are newly planted, particularly rare or precious. If there’s any water left in the tanks the remaining plants might get a drink.
First published in The Chronicle 17th October 2009.
