The understorey story

The Garden of St Erth is nestled deep in the Wombat State Forest and surrounded by peppermint gums and Blackwood wattles. It seems an unlikely place to find a large English garden.

It represents perhaps a uniquely Australian horticultural problem; how to integrate an exotic garden full of colour, diversity and intentional form into the comparatively unkempt and wild surrounds. The Australian bush, beautiful in its own way, stands in stark contrast to our idea of kept gardens. Its limited range of species, grey and green colour palette, and harsh dry nature do not easily blend with our favoured exotic plants, neither visually nor in their cultural needs.

There is always a temptation to block out and separate the surrounding forest from our gardened areas. Hedges, walls and ‘garden rooms’ can create a charming oasis in the bush; within the bounds, a fertile exotic garden filled with flowers, food and well-kept lawns. Integration with the borrowed landscape around us is not always desirable. The Garden of Eden was, after all, a walled garden. The contrast of driving through dry, harsh terrain and wild forest to then arrive at a beautiful oasis within the neatly hedged borders of the garden is quite an experience.

The eucalypt challenge

Faced with dense eucalyptus growth over a significant area of St Erth, learning to work with eucalypts and gently integrate parts of the garden into the remnant bushland became necessary. The challenge was not only to find plants and designs to bridge the gap between garden and woodland but also to find species that would not just survive but thrive in the adverse conditions.

Much has been written about eucalypts and their unsuitability as a garden tree. Their poor shade, inability to build fertile soils, competition and, of course, flammability are good reasons to avoid planting them in backyards and cultivated gardens. Our bush garden was no exception. The original mining rubble soil was unimproved and perhaps made even worse by the acidification from the eucalyptus leaf drop. Any attempt to improve the soil or irrigate would be taken up rapidly by the eucalyptus. The dappled shade and dry conditions further limited our range of plants to choose from.

Developing a climate-proof understorey

Gardeners over the decades had tried various plantings with limited success. Tommy Garnett, the garden founder, dedicated the area to rhododendrons. Acid-loving, shade tolerant and certainly in vogue during the 1970s and 80s, they provided a glossy green understorey to the native trees; briefly flowering with a range of gaudy colours each spring. Native to the Himalayas, rhododendrons prefer a soil high in organic matter but proved surprisingly adaptive in the unimproved Blackwood clay.

Despite the initial success of the rhododendrons, their insatiable water requirements soon became a problem. In their native habitat, they enjoy regular rainfall and humid summer conditions. Although Blackwood has higher rainfall than much of central Victoria, we still suffered from the effects of climate change with spring and summer rainfall becoming more erratic. During the millennium drought, much of the planting went into decline, with many plants dying after months without rain.

Learning from drought

Facing a changing climate with hotter, dryer summers and increased bushfire risk, we enlisted the help of landscape architect Andrew Laidlaw to landscape the area using a selection of plants appropriate to the climatic conditions. Recognising the beauty of the many straight vertical eucalyptus trunks, Andrew decided to make them a feature, limiting the height of the understorey and contrasting them with flat mudstone along the pathways. A combination of ground covers and small shrubs provides a variety of forms and textures, blending more intensively cultivated exotic areas of the garden with the native vegetation. Lower-growing plants beneath the eucalypts help to mitigate the risk of bushfire by keeping other foliage away from the flammable canopy.

Plant selection was not limited to native Australian plants, although many natives were included. Andrew’s experience in gardening with native species and the combined local experience of St Erth’s garden team were drawn upon to find an appropriate range of plants for the tough spot. Australian mint bush (Prostanthera) and a selection of correas, native grasses and coastal rosemary (Westringia) combine with exotic plants from other dry climate parts of the world. Honey Bush (Melianthus major), native to South Africa, provides the contrast of larger, lighter coloured foliage with its flowers enjoyed by the native birds throughout autumn. New Zealand lillies (Arthropodium) and New Zealand cabbage tree (Cordyline australis) add a strappy, verdant dimension without the need for additional irrigation or soil improvement.

The ‘new’ planting is now over 10 years old and continues to evolve and grow. While perhaps an unusual combination of plants, each is chosen for its ability to thrive in the poor soil, dry shade and competition of native trees. Despite these limitations, it’s possible to grow a beautiful garden by choosing the right plants for the climate and conditions.

Written by Julian Blackhirst, head gardener at The Garden of St Erth.