xeriscape gardening

Who dictates our garden styles?

This is a personal perspective from a serious sustainable landscape designer and should be read in this vein. The post is designed to be contrary and to make people think!

Most people have a tendency to copy trends with their gardens. A few individuals are brave enough to design their own garden that is different – and it is these gardens that buck the trend, that stand out.

When you look at the gardens that the English put forward at places like the Chelsea Flower Show, their gardens often have a much more simplistic and natural style about them – plants are used to make the pictures. So why are so many Australian gardens about the use of hard landscaping en masse with structures and decking used instead of plants?

McMansions as homes have come under a lot of scrutiny and criticism. Mostly because they make a statement – “look at me, I’ve got money!” Unfortunately gardens have followed this style to ‘complement’ the garishness of the homes. What has happened to ‘understated beauty’?

Consider the gardens that win the awards in Australia through the Landscape Associations and Landscape Architecture. With the exception of a  few, where specialist sustainable designers enter their gardens, the bulk are an expose of manufacture. And the bulk of these landscapers are from the building trade, many with little or no knowledge of plants and their ongoing care. With their knowledge being based on structures, walls and so on, no wonder the bulk of the award winning gardens are so artificial.

When home gardeners view these winning gardens, the assumption is that this is the way to do it. And so we get the home-owner do-it-yourself makeover that is a rendition of something that they have seen that the media fussed about because it won. These manufactured gardens look artificial, with plants often lasting less than 5 years.

If the home gardener just kept their ideas simple, then they would have a much better garden, and be proud of their efforts. There is so much competition in life these days with everyone trying to outdo others, the simplistic aspect of living is being lost. Gardens should be simple places of enjoyment. Not ‘Tea Houses’ or broad expanses of decking, concrete walls, with chunky chairs and tables for plants!

I feel that the encouragement through the awards processes, for both display gardens and real gardens, is enabling the artificial building aspect of gardens to be seen as the norm. I believe that we need to turn back the clock and realise that all of this totally unnecessary energy use is having a seriously detrimental effect on our environment and we need to reconsider what a good garden really is. The question needs to be asked “Are we making gardens, or extending our homes?” which of course is most definitely the case. And the McMansion owners are encouraging it. Obviously, I am not a supporter.

Trees in the landscape for native gardens

[post based on a native garden perspective]

I admit it; I am an unabashed tree lover! As a landscape designer, I find it frustrating when people can’t understand the need for trees in their gardens. The usual negative comment from the client is ‘the leaves will be a nuisance in my gutters!’ Clients who love trees from the outset or are happy to be guided into their use, end up with wonderful gardens. But some people are hard to convince.

Most people don’t understand that the vertical aspect of trees within their garden actually makes their gardens appear bigger – because it’s a further dimension that is being addressed with plant material. And the vertical accent also creates depth in a garden which is missing in most novice and too often professional gardens that are created.

Consider walking into a garden, as you do, without trees. Your eyes are constantly kept at ground level or a bit higher. Real trees, those above 5 metres, cause you to bend your neck to look upwards into the canopy. The art of taking a path to go under the canopy of the tree is without doubt one of the greatest means of creating depth in your garden. And canopies can be raised as the trunk grows, enabling you to walk underneath.

Trees are wonderful for insulating the home. Evergreen trees, as in the Eucalypt, Cupaniopsis anacardioides or ‘Tuckeroo’, tall melaleucas like Melaleuca styphelioides, Agonis flexuosa, Allocasuarinas and Casuarinas and so on, are great for the eastern or western boundaries. The deciduous tree, indigenous to Australia and South East Asia called Melia azederach or ‘White Cedar’ grows to around 12 metres tall with a spread of around 6 metres. It grows mainly along the northern aspects of the eastern seaboard, but I have grown it well in areas that receive considerable frost. Given some summer irrigation, this tree is excellent for providing summer screening of windows on the northern side of the home, while allowing winter sunlight in, for those wanting to keep the native garden theme ‘pure’.

I have always noticed that children prefer gardens with trees in them. They seem to have a better understanding of the creation of different spaces within a garden, with trees helping to break up not only the vertical aspect, but also different areas within a garden. I find that if you can make different rooms within the garden, this also adds to the appeal of the area, and the use of trees here is essential.

There are some marvellous smaller Eucalypts that can be used, for example, Eucalyptus victrix, Eucalyputs pauciflora ‘Little Snowman’, Eucalyptus gregsoniana for colder climes, and Eucalyptus leucoxylon ‘Goolwa Gem’ which is a low growing form. I have a passion for plant research, which ensures that I choose plants that will work well in either my own garden, or that of my client. It is important to consider their original habitat when trying to work out which plant to use in the garden. For example, the much used but invariably badly grown Eucalyptus caesia seems to do well for a couple of years and then ultimately fails. I never use this plant as I find it too unreliable.

Trees that have an open canopy allow filtered light in to the plants growing underneath. Unfortunately, many a good tree specimen is ruined by the incorrect placement of plants underneath. Many gums have magnificent bark and/or trunks. The pictured Eucalypt for example has very interesting trunks, worthy of being made a feature; so to me the most ideal planting under this specimen would be the use of massed native grasses or grass like plants. And Lomandras are of the lily family and are not grasses. But they, en masse would look wonderful under this tree.

For those of you who don’t have any trees in your garden, try just one, a variety with an open canopy, and see what a difference it makes to your garden. Trust me, I can guarantee that you will be pleased with the result.

Declining groundwater is a big problem for Australia

Opinion
By Derek Eamus

Groundwater is extensively used right across the Australian continent, which is why we should take very seriously a new study which says supplies are on the decline, writes Derek Eamus.

The loss of groundwater stores poses serious threats to humans that need it to drink, crops that are irrigated with it, and natural ecosystems that rely on it for their survival.

That’s why a new NASA study is cause for concern, particularly in a dry country like Australia.

Two satellites, launched in 2002, are able to make detailed measurements of the Earth’s gravity field in the Gravity Recovery and Climate Experiment (GRACE).

Short-term fluctuations in the Earth’s gravity field can occur in response to large-scale changes in sea-ice and sea-level rise. However, changes in the gravity field in terrestrial locations far away from oceans and ice have been detected. These fluctuations occur in response to changes in the total mass of water stored within lakes, soil and groundwater.

Using independent data sets, it is possible to remove the effects of lakes and soil water store from the GRACE signal, thereby providing, for the first time ever, large-scale assessments of the changes in total groundwater store within massive aquifers at monthly, seasonal, annual and inter-annual time-scales.

About 40 per cent of the world’s population live in arid and semi-arid regions where groundwater is vital for human consumption but also for the maintenance of ecosystem health. It is not widely understood that vegetation and many streams and rivers are supported by the availability of groundwater, either as discharge into streams and rivers or through groundwater uptake by plant roots directly.

Australia is of course a very dry country so it is no surprise to find that groundwater is extensively used right across the continent. Perth relies heavily on the Gnangara Mound aquifer for its water supply, but the water table has been dropping for the past 40 years or more because of reduced rainfall, increased extraction, and probably because of decreased recharge arising from vegetation water-use.

The Great Artesian Basin (GAB), underlying about 1.7 million square kilometres of Australia, contains about 65,000 km3 of water, but the water is up to 2 million years old so it is easy to extract this resource far faster than it is being replenished.

As the pressure in the GAB has declined and the water table drops, mound springs (where groundwater is pushed to the ground surface under pressure) have begun to dry up in South Australia and Queensland. Associated paperbark swamps and wetlands are also being lost and it gets more and more expensive to extract the groundwater for irrigation and other commercial applications.

On average, rates of groundwater extraction across Australia has increased by about 100 per cent between the early 1980s and the early 2000s, reflecting both the increased population size and commercial usage of groundwater stores.

The GRACE satellites have also been used to monitor the impact of the Australian millennial drought on the Murray-Darling Basin (MDB). The MDB accounts for about 30 per cent of the gross value of Australia’s agricultural production. From 2001 to 2006, the total rainfall deficit (the difference between the actual volume of rainfall received and what would be expected in rainfall was the average) for the basin was estimated to be about 520 km3. Using GRACE data Marc Leblanc and co-workersshowed that there was an almost total loss of surface waters (lakes, rivers) within two years of the start of the drought but depletion of groundwater stores continued for six years or more after the start of the drought. Between 2001 and 2007, there was about 104 km3 of groundwater lost from the MDB. The average annual loss of surface water and groundwater was 20 km3 which is 150 per cent of the total water usage in a normal year. Despite rainfall rebounding in 2007 and 2008, the GRACE data showed a continued decline in groundwater storage.

The international study released by NASA showing declines in groundwater resources globally should alert us to the pressing need to manage groundwater resources sustainably. Australia is not immune to the challenges posed from declining groundwater resources.

Derek Eamus is Professor of Environmental Sciences at the University of Technology