Indigenous Fallacies

The Age

Saturday November 6, 2004

Michael McCoy

Michael McCoy gets to the root of the growing-natives debate.

It's way past time to put to rest one of the great fallacies of horticulture, and one that the native plant school and particularly the indigenous plant school lean heavily on to persuade us to join their ranks.

The "grow-native" types claim that given the limited water available for gardens, native plants are naturally drought tolerant and are therefore an obvious choice for gardens. But the indigenous plant growers will bring it out in its purest form: that plants in their native habitats are perfectly matched to the conditions, and therefore there are none better than those that would have grown there naturally.

I wonder if aliens, scouring the universe for intelligent life forms and happening across the Inuit people first, would take a few samples back, establishing them in an enclosure of sub-zero temperatures on the assumption that the conditions they found them in were those they preferred? Humans are, of course, best adapted to life in equatorial warmth but are tolerant of temperatures way beyond these zones.

Likewise plants - they often do well outside their "native" habitats. Indeed, they'll sometimes do too well in the absence of the factors that keep them in check in their native environment, becoming environmental weeds.

It often comes down to the difference between plants tolerating their conditions, which is the case with many if not most of the plants in the wild, and plants relishing their conditions. You don't have to study plant ecology for long to discover that the entire plant world exists under enormous competition. That a particular Eucalyptus species grows in your area, for example, may not be because it is a "chosen" site, but that in every area it would "prefer" to grow in, it is ousted by plants of greater competitive value. Perhaps a better human analogy, then, would have been my aliens picking up some 19th-century Irish tenant farmers and replicating their apparently favoured conditions, then wondering why they failed to thrive on the sodden, nutrient-starved peat bog they carefully provided. That these farmers were forced into less than perfect conditions by English landlords wouldn't be immediately obvious.

Plants can also become separated in the wild from their preferred conditions by simple geographical barriers. Large-scale shifts such as the movement of tectonic plates, or changes on a micro scale, such as erosion, can create barriers that force plants from the conditions that suit them.

So to argue that native or indigenous plants are those best suited to the local conditions is fallacious. What's more, used as a reason to grow such plants, it may backfire. If you are looking for plants that will thrive in your local conditions, look for those adapted to even harsher conditions and will therefore find life in our often dry, poor soils a breeze.

This, however, makes the perfect conditions for ecological weeds - think of Paterson's curse or the prickly pear early last century, or Cootamundra wattle ( an Australian native - one of our worst weeds).

None of this is to say that there are not good reasons for growing native or indigenous plants. Respect for biodiversity, beyond its simple potential usefulness to humans, might make you think about growing them.

Such thinking might also bring about a time when earthmovers on road and construction sites do everything possible to preserve the natural state of the soil profile around where they're working, which is critical for the preservation or

re-establishment of many of our extremely soil-sensitive plant species.

The "best plants for the job" argument for growing indigenous plants doesn't cut it. If they stick to it, groups who would see us use more natives will fail to achieve their aims.

© 2004 The Age

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