Episode: VIC Waterwise Special ? Our Changing Climate
Presenter: Neville Passmore

Plants are amazing organisms and nowhere can this be seen more than in the ways that plants cope with water shortages. By understanding these adaptations that have evolved over many thousands if not millions of years we can better identify the varieties we need to use in our waterwise gardens of the future.

The delightful garden in Ceres near Geelong called Hill House can be viewed under the Australian open Garden scheme in summer. It contains some beautiful and tough plants.

The shape of a leaf can actually have quite an effect, for example large flat leaves like the Monstera or Fruit Salad Plant (Monstera deliciousa) lose the most moisture and in the fastest time when subject to water stress. Small leaves make it easier for the plant to control moisture loss. The most water efficient shape is the rolled or needle shaped leaf as it cuts the surface are to the absolute minimum. An excellent example is Grevillea thelmanniana.

She-oak (Allocasuarina torulosa) goes one better its leaves are reduced to these tiny almost microscopic scales on a needle like modified stem. That goes some way to explaining how these trees and shrubs can exist in deserts as well as the windiest beachside areas.

A fine coating of silver powder over the leaf surface reflects light and heat and enables the plant to keep cool thus conserving moisture, like the Wormwood (Artemisia cv. ?Powis Castle?).

Another strategy is to store moisture in the foliage and a great example of this is Pigs Ears (Cotyledon orbiculate). These are members of what we call the succulent family.

The storage enables the plant to get through long periods of drought.

Bulbs are generally very conservative drinkers in their home territory as they drink up when water is available then go through a long period of dormancy before erupting into flower when moisture and temperature trigger new seasons action. Clivia or Fire Lily (Clivia miniata) is a great performer in dry shaded areas.

Many Australian plants such as the mallee types of eucalyptus have swollen underground trunks called lignotubers packed full of what I call just in case buds. If the plant were to be burned to the ground or die back through dryness these buds burst into new growth to regenerate the plant and enable it to survive.

So that is just a few of the water saving strategies used by plants to reduce their requirements and they do it with beauty and grace.