Smart planting in big dry

Sustainability is something of a buzzword in landscape and garden design, but for the citizens of Melbourne it's not just a feel-good theory, it's a necessity.

The city is recovering only now from a drought that started in 1997. Predictions are, however, that the break in the dry weather is the anomaly and that the city is facing a 30-year dry spell.

Over the past 14 years inhabitants have learned the hard way what a precious resource water is - but in the driest decade on record Melbourne has also become one of the most water-wise cities in the world.

Spend some time in the CBD and this miserliness with water quickly becomes apparent. Automatic taps in public bathrooms have very short cycles, drought-tolerant plants dominate in gardens, there's not much lawn and corporate landscapes have done away with water features.

The city's Botanic Gardens, considered to be among the best in the world, is taking a proactive stance on its water use and embarked on a project that will severely reduce its need for water from outside its gates.

Water from the garden's own reservoir is used for irrigation, with run-off directed through two ornamental lakes and their associated "polishing" wetlands before being recycled back to the reservoir.

William Guilfoyle, who became director of the gardens in 1873, created "Guilfoyle's volcano", a Victorian folly of sorts that had serious intent with the cone hiding a reservoir for gravity-fed irrigation.

Andrew Laidlaw, the garden's landscape architect, has recently uncovered and rebuilt the 8m-high volcano and reservoir after 60 years of neglect.

"It's amazing to think we had all lost sight of it," he says. "It was completely overgrown and forgotten about."

He has replanted the sides of the reservoir, which holds up to 1.3 million litres, and around its base with an arid garden that includes cacti, succulents and bromeliads, while the reservoir features five floating "islands" of plants that help purify the water.

With a budget of NZ$321.969, Andrew was able to buy in larger specimens of several plants, including Alcantarea imperialas (giant bromeliad), Queensland bottle tree (Brachychiton rupestris) and Cussonia paniculata (South African cabbage tree), although two-thirds of the almost 17,000 plants, representing 250 species, were propagated at the garden's nursery.

"There are repeating plantings of some, including golden barrel cactus, Yucca whipplei and various kalanchoes, to bring rhythm," he says.

Most of the plants are native to the dry regions of Africa, South and Central America and Australia. The gardens are mulched with crushed bricks and a boardwalk spirals up the volcano to observation decks.

Designed to mimic lava flows down the volcano, the plantings, Andrew says, give a sense of "liquid movement". Guilfoyle had created this effect with lawn.

"William Guilfoyle worked with a palette of plants," Andrew says, "and we wanted to show that idea being used in a design way. Many botanic gardens become a collection of individual plants but we wanted to reduce the number of competing elements so you see more."