Choosing Sustainable Landscape Materials

Environmentally Friendly Practices for The Garden

The materials featured have been chosen for their current popularity. In an attempt to lessen the environmental impact of their use when building or designing outdoor spaces, follow these simple guidelines.
• Ensure materials required are accurately estimated to avoid waste.
• Choose the smallest size of components for a job.
• Construct landscape elements to standard dimensions to reduce waste.
• Look at the materials already on site and consider ways to re-use them imaginatively.
• Choose materials that involve minimal industrial refinement and processing.
• Source recycled materials wherever possible rather than newly processed products.
• If possible use products from your local region. Enquire with your retailer about their source.

Timber

Timber is widely used in gardens for the construction of structures such as pergolas, decks and screens as well as for steps, edging, outdoor furniture and formwork. Compared to other materials such as stone or metal, timber can be easily worked, is relatively cheap and widely available.

A wide range of timber products are available in the Canberra region with little information available at point of sale on product source.

When choosing timber to use in your garden consider:

Soils

In nature, it takes around 1000 years to produce 1cm of topsoil (TAFE NSW Et EPA 1997) therefore it is important to protect existing soil resources.

Consider the following when contemplating alteration of the existing soil type or surface levels.

• Where possible work with the existing landform rather than significantly altering it.
• Equalise cut and fill to avoid importing/exporting soil.
• Stockpile and reuse topsoil when performing earthworks.
• Add organic matter such as composted green waste and local manures to improve soils. Manures are available from local paddocks, shearing sheds and agricultural shows.
• Match plants to soil conditions, for example, for shallow soils with rocky outcrops use plants that thrive in these environments.

Clay Products

Clay products include bricks, pavers, pots and tubs, terracotta ware and ornaments, all of which require the extraction of materials from non-renewable resources and significant energy inputs when firing.

Paving is perhaps the most common landscape use of clay and has been used for thousands of years to create outdoor terraces and paths. Clay pavers laid on sand can be easily removed to access underground services.

When choosing paving for your garden consider:
• limiting paving to areas where you will sit, stand and walk
• re-using existing pavers either from your site or from the local region
• using spare or recycled pavers as garden bed edging
• requesting a number of seconds (with slight flaws) when buying new pavers and using these in inconspicuous areas
• if choosing new products, opting for products manufactured locally.

Concrete Products

Concrete is available as cured pre-cast units, (blocks, pavers and retaining wall systems), as well as poured in place. Both methods involve quarrying aggregate from non-renewable sources, and production of Portland cement powder using high energy kiln-firing.

A reduction in the environmental impact of concrete may be achieved by:
• preparing your own wet concrete mix including chunks of cleaned broken brick, recycled glass and salvaged sand instead of new aggregate
• using only as much cement in the mix as required for the project
• allowing for future crushing and recycling of the concrete by avoiding steel reinforcement (pour concrete slightly thicker, or use a slightly higher strength mix)
• avoiding disposal of concrete waste into waterways, open spaces and drains.

Ornamental Pebbles and Gravel

Gravels and pebbles feature as ground surfacing in many contemporary landscapes. When choosing gravel for your garden consider:
• using the minimum depth necessary
• using on-site soil to fill holes and create levels rather than filling large voids with imported gravels and pebbles.

• using crushed brick or concrete made from recycled bricks, roof tiles and concrete
• avoiding river gravels mined from existing river systems - ask the supplier where the material has come from
• avoiding material sourced from overseas locations
(often highly polished pebbles in bags).

Sand, Crushed Rock and Stone

Quarrying processes are used to extract sand, (used in concrete and beneath pavers), crushed rock, (used as a base beneath paving and in drainage systems), and large stones, (used for paving, walls and garden features). These elements are non-renewable.

When using sand, crushed rock or stone in landscape construction consider:
• using only the minimum depth necessary
• where safe, laying stone without mortar or concrete to allow for future reuse
• reusing old gravels and sand from beneath paving you have demolished
• sourcing stone which is a by-product of quarrying processes
• reusing or recycling unwanted flagstone and ornamental stones
• using recycled brick or concrete behind retaining walls and in other drainage systems instead of new quarried material.

Remember it is illegal to remove bush rocks from the bush. They provide habitat and soil stabilisation.

Mulch

Mulch can reduce evaporation from garden soil, adds organic matter whilst suppressing weed growth and reduces erosion. Mulch should be spread to a suitable depth. Generally 75mm is adequate.

When choosing a mulch for your garden consider using:
• shredded prunings from tree surgery and green garden waste
• by-products of managed plantations rather than natural forests
• leaves collected from street and roof gutters
• pine bark, a by-product of pine processing for timber.

Newspaper, cardboard and natural fibres laid beneath mulch can also contribute to weed suppression. Non-organic gravels, such as crushed brick and crushed concrete can also be used as mulches.

References

TAFE NSW & EPA (July 1997) Waste minimisation guidelines for building and construction.

Good Wood Guide:

www.rainforestinfo.org.au/good-wood/sel_spec.htm

This information was prepared by Edwina Richardson, David Moyle and Jennie Curtis from the ACT Group of the AILA and was published in hard copy with the assistance of funds made available by the ACT government under the ACT Government Environment Grants Program.