Botanic Gardens Trust, Sydney, Australia

Education




Walk on Water

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Strategies and plants you can use in your garden to conserve water

This self-guided walk through the Royal Botanic Garden was developed as part of Big Answers to Big Questions. You can print a map and take the tour, or just enjoy it here on our website!

We don't need a miracle to save water in our gardens. The Royal Botanic Gardens & Domain Trust has been employing effective water-saving strategies throughout the Garden and Domain for several years. Also, many plant species within the Garden are adapted to harsh climates and are ideally suited to home gardens because as well as being attractive, they have water-wise attributes. 

1. Native Knowhow - performing under pressure

Many native plants are a good choice to include in your garden - some have striking features such as long-lasting flowers and ornamental foliage. Unlike exotics, plants native to Australia have had millions of years in which to adapt to our harsh climate and nutrient-poor soils:

  • They do not need fertilisers - in fact, some native plants are sensitive to extra nutrients
  • Some native plants are slow growing and drought-resistant once established
  • Many have hard waxy leaves which contain oils, resins and tannins which minimises water-loss through evaporation.

2. Mucho Mulch - it’s got you covered

Covering bare soil with mulch is an effective way of saving water in your garden. The broken tiles used were donated after the 2001 hail-storm destroyed hundreds of roofs in Sydney. The tiles retain heat and do not add any nutrients to the soil - making them ideal mulch for the Succulent Garden. Mulching has three beneficial effects:

  • It slows down the loss of moisture from the soil by evaporation
  • It suppresses the growth of weeds
  • Organic mulches such as leaves and wood-chips increase the soil’s water-carrying capacity.

3. Bone-dry Cacti - don’t add water

The Succulent Garden is a microclimate; a mini-desert. It is in direct sun all day, the dark paving radiates heat and we use no watering system at all! Cacti are succulents that are perfectly adapted to cope with the desert environment:

  • Cacti leaves have evolved into spines that do not lose water through evaporation
  • Fleshy stems and roots store water
  • Some cacti are a grey-blue colour - this reflects heat and light to keep them cool
  • The concertina-like shape of some cacti such as the Barrel Cactus (Ferocactus glaucescens) allows them to expand when it rains and shrink during drought.

4. Cycads - ancient survivors

Cycads have existed since before the age of the dinosaurs. For over 250 million years, they have adapted to cope with conditions that other plants would find impossible. They are also highly decorative, with glossy foliage and textured trunks. This mean that cycads are perfect for low maintenance gardens:

  • Many grow on rocky terrain or in sandy soils, some are even salt-tolerant
  • Most cycads are drought tolerant
  • Their specialised root system ‘fixes’ nitrogen so they can grow in nutrient-poor soil.

5. Strange Adaptations - the water-bottle tree

Did you know the Bottle Tree (Brachychiton rupestris) is a succulent? It grows naturally in very arid environments and like all succulents it stores water in its trunk and roots. If a grown tree is uprooted, it can live on the water stored in its trunk for up to three months!

The Indigenous people of Queensland knew that the Bottle Tree was a valuable water source. By boring a hole in the trunk, they would extract a nutritious jelly-like sap. The seeds, young roots and shoots of the Bottle Tree are also moist and edible.

6. The meeting of the waters

Here you can see the meeting of Botanic Garden Creek and the waters of Sydney Harbour. Many harmful chemical pesticides and fertilisers used in Sydney residents’ gardens leach through the soil into urban waterways and make their way to the sea.

To ensure that water which flows through the Gardens to the Harbour is not further degraded, we use biodegradable and organic fertilisers and pesticides. We also do regular testing for water quality as part of Sydney Water’s Streamwatch program. School groups are welcome to join us for a Streamwatch session - contact 9231 8134.

7. Herb Gardens - east meets west

Many herbs originate from the Mediterranean and the Middle East. Sweet-smelling, edible and medicinal plants such as lavender, thyme, oregano, sage and rosemary have adapted to thrive in harsh environments. This means they are very suitable for Australian gardens:

  • The stiff leaves have high oil content so they lose less water through evaporation as well as having a delightful scent
  • Grey-blue coloured foliage reflects heat and light, keeping the plants cool
  • No pesticides are necessary as the oil in their leaves is a natural deterrent to bugs
  • Many need very little water or fertilisers.

8. Native Grasses - flavour of the month

Native grasses are back in favour! They lend strong architectural elements to contemporary garden design with their vertical foliage and showy flower heads. Native grasses are the perfect choice for a sustainable garden:

  • No fertiliser is necessary as they have adapted to Australia’s nutrient-poor soil
  • Deep root systems mean they can survive droughts and fire
  • Kangaroo Grass (Themeda australis, cultivar mingo) and Redgrass (Bothriochloa macra) are both good lawn substitutes - they only grow to 10 cm high and form tufting, dense mats of foliage. They need very little water and you because of their naturally low growth, you will never have to mow again!

9. Garden of Eden - fabulous gardens with less H20

Eden Gardens designed and built a temporary display garden as part of the ‘Big Answers to Big Questions’ program. It demonstrated three garden designs which are all sustainable, using little water while still looking fabulous. Some of the simple but effective water-wise features of the garden included:

  • Water crystals and wetting agent in the soil
  • Mulching to retain moisture
  • Use of plants which have naturally lower water requirements.

10. Rose Garden Revamp - suitability equals sustainability

Plants that are suited to our climate and soil type do not need extra water, fertilisers or pesticides. Some of the roses formerly planted here were not suitable for Sydney’s climate and were vulnerable to soil-borne diseases.

When the Rose Garden revamp is complete, it will feature Australian cultivars that enjoy Sydney’s climate. The roses will be healthier, produce more flowers and generally cope better with less watering and less pesticides.

11. Lawns - a ‘no water’ zone

Once a lawn is established, you can leave it without water and even when it looks almost dead, good rainfall will revive it to its glossy green best. The Trust has implemented several water-saving strategies which apply to our lawns:

  • We have several areas of ‘no water lawn’ - during the recent drought these lawns went completely brown but have now nearly recovered
  • Where lawn watering is essential it takes place in the evening or early morning to minimise evaporation
  • We use wetting agents in the soil to ensure that water penetrates evenly.

12. Microclimate - a rainforest in miniature

Grouping plants with similar water needs together in your garden will create a microclimate - a miniature ecosystem which mimics the way nature is organised. If you create a small rainforest in your garden, the plants will shade and support each other and will need less watering:

  • Choose a sheltered, shady area - try the southern side of your house
  • Use deep organic mulch like leaves and woodchips to retain moisture in the soil
  • Group ferns and similar plants close together to create a humid environment.
 

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