Introduction
When planning your garden it is vital to select plant species which are suited to Canberra’s soils and climate. Plants must be drought and frost hardy. Plant material will thrive with a combination of careful selection, soil preparation, mulch application and the incorporation of drip irrigation. Avoid weedy species - there are many species which were planted in early Canberra gardens and should be removed, these include Ligustrum (Privet), Pyracantha and Cotoneaster. Native species can also become weeds such as Acacia baileyana (Cootamundra Wattle) and Grevillea rosmarinifolia.
>> Brochure on Weeds in the ACT
All plants need some level of maintenance if they are to perform well, such as tip pruning after flowering. These practices will help ensure healthy plant growth and save money.
Consider raising plants from seeds and cuttings (plants like Correa are easy to grow from cuttings). Many natives will grow readily from seed and are available in packets from nurseries. Small plants such as tubestock are inexpensive to purchase and will quickly outgrow bigger plants.
The majority of Canberra soils are poorly drained clay soils which may become waterlogged during winter and hard and cracked in hot weather. Soils can be improved with the addition of organic matter (such as homemade compost, manures such as sheep manure, straw and lucerne, green manure crops) as well as products like gypsum.
It is better to reduce the number of plants requiring well drained soils such as many of the West Australian native plants (such as Anigozanthus, Kangaroo Paws) as they often require substantial soil modifications which are not sustainable. These types of plants are better limited to a group of pots where good drainage can be supplied by incorporating a good native potting mix.
Annuals which also require relatively high levels of maintenance may be best placed in groups of pots or beds close to the house where their needs can be regularly monitored. Consider replacing annuals in pots with succulents. These plants require low levels of water and relatively little care. Some succulents may require protection from frosts and should be placed under cover.
Plants should perform multiple functions in our gardens. So as well as choosing appealing visual features like attractive foliage or weeping habit consider how these plants may provide privacy from adjoining neighbours, act as windbreaks, provide habitat, produce edible foods, bind soil and trap nutrients. Bush food plants could be incorporated in a section near the house and may provide habitat for local fauna.
Many locally occurring native plants as well as exotic plants from dry regions in other parts of the world can be combined successfully in our gardens. It is best to choose plants that occur in regions with low rainfalls and similar soil types. Observe how plants are performing in local nature reserves. Plants like Cassinia, Dodonea and Hardenbergia are exceedingly tough at coping with extreme conditions.
The Xeriscape Garden, Canberra Institute of Technology, Heysen St, Weston demonstrates the use of a range of both native and exotic plants suitable for Canberra’s climate.
Whilst the Australian National Botanic Gardens has a list of native plants suitable for dry conditions.
Many local plants can be obtained from specialist native plant nurseries or may be grown from purchased seed. Also look at plants which are growing successfully in neighbouring gardens, as well as gardens in Australia’s Open Garden Scheme. There is a display of commercially available native plants suitable for the Canberra region at the Ellis Rowan garden, Australian National Botanic Gardens.
What do low water plants look like?
Generally speaking plants from low water areas exhibit a number of adaptations: they may have:
- blue, grey or silver foliage
- hairy or small or needle-like leaves
- succulent leaves (with water storing ability)
Conversely, plants which require large amounts of water tend to have large green leaves.
Right: Leucophyta brownii (Cushion Bush) is a drought hardy native from Victoria - it has silvery foliage and narrow modified leaves and can be clipped into a ball shape if desired. |
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Seeking professional help?
If you are not confident in preparing your own plant list and layout a Landscape Architect can help you by preparing a Planting Plan for your garden.
>> For a list of Canberra Landscape Architects
Choosing Trees
Value of trees
Trees should play an increasingly important role in Canberra gardens to help counteract the effects of a warming climate. Trees have multiple benefits, including: shade provision, reduction of building temperatures and wind speeds, acting as carbons sinks, soil protection, provide habitat and wildlife corridors and improve property values. They also provide vertical landscape elements which can soften the appearance of large buildings and frame views. It is important that trees are chosen that are a suitable scale for residential gardens. Gone are the days of planting large eucalypts such as Eucalyptus nicholli and Eucalytpus mannifera which soon outgrow the garden and become hazardous.
A hardy Lagerstroemia indica (Crepe Myrtle) is retained and incorporated into the landscape treatment of this multi-unit development in Braddon. Crepe Myrtles vary in size from dwarf varieties less than one metre high to medium sized trees up to eight metres tall. Photo Edwina Richardson. |
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Role of deciduous and evergreen trees
Both deciduous and evergreen trees can be incorporated in the garden. Deciduous trees, which lose their leaves during Winter, allow sun to penetrate the home during the cooler months of the year, whilst providing shade during Summer. Deciduous trees should be sited to the east, north east, north and northwest of the house. Avoid planting species which are a potential weed. Evergreen trees should be planted to the west, south west and south of the house where they don’t interfere with solar access. It's also important to consider the amount of shade a tree planted in your garden may affect an adjoining neighbour.
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As block sizes are diminishing and houses getter larger it’s important that small and medium sized trees are incorporated into landscape plans. Trees need to be relatively drought hardy and able to handle increased temperatures as well as frosts. Plants which may be suitable include evergreen species like: mallee Eucalyptus and Eucalyptus cultivars, Laurus nobilis (Bay), Brachyciton populneus (Kurrajong), and deciduous trees like Melia azerderach var. australasica (White Cedar), Malus (ornamental crab apples), Pyrus (ornamental Pears) and Lagerstroemia (Crepe Myrtles). More research is required by commercial tree growers to find which trees will be able to grow successfully with increased temperatures and drought in southern Australia.
Planting and maintaining trees
When planting a tree ensure it is given a helping hand with good soil preparation (incorporating plenty of organic materials, mulching with minimum 75mm depth mulch and deep watering using a drip irrigation system. If trees are to be planted close to paved areas or near the house install 500mm deep root guard, this will encourage roots to move down into the soil profile rather than on the surface disturbing structures. It’s best to plant trees in mulched shrub beds rather than in the lawn as they have very different watering requirements.
Lagerstroemia 'Tuscarora' growing at Yarralumla Wholesale Nursery. This cultivar bears dark coral-pink flowers in late Summer and Autumn, has colourful Autumn foliage, decorative bark and is resistant to Powdery Mildew. Photo Edwina Richardson.
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>> For a list of small to medium Eucalyptus species suitable for home gardens
>> Social, Health, Economic and Environmental Values of trees
Choosing Shrubs
Trees and shrubs should form the backbone of the garden. Whilst the trees in a garden will provide vertical interest via their trunks and an overhead canopy, shrubs are generally used to screen fences, adjoining residences and unattractive structures. Massed shrubs provide the majority of mass in the garden. As a general rule, large shrubs are planted at the back of garden bed next to the fenceline. Large shrubs grow to a minimum height of two metres, with smaller shrubs planted in front.
It may be worthwhile to overplant initially as gardens take around five years to reach a semi-mature state in the ACT. By combining a variety of fast, medium and slow growing species you can create shrub borders which evolve over time. Species like Acacia (Wattles) and Cassinia are generally fast growing - they will provide protection for slower growing plants and can be selectively removed as the plant material matures.
Choosing Accent Plants & Groundcovers
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Accent plants tend to have a strong architectural shape and elongated strap-like leaves. A wide range of accent plants have become popular recently such as cultivars of the Australian natives Dianella and Lomandra. These plants once established can cope with dry conditions as can a number of exotics, such as Dietes.
Groundcovers are low evergreen plants which usually hug the ground and protect the soil from erosion, evaporation and suppress weed growth. These types of plants are useful replacements for grass on nature strips.
Left: Front garden & nature strip where lawn was replaced with drought hardy groundcovers such as Myoporum parvifolium (Fine leaf form), Scaevola 'Mauve Clusters', small shrubs such as dwarf lavender and Convolvulus along with accent plants like dwarf Agapanthus. Design Landscape Architect Jennie Curtis. Photo Edwina Richardson. |
>> More native accent plant cultivars
Choosing Climbers
Climbers are plants which generally grow vertically up a structure. Some climbers are self clinging, such as the deciduous Parthenocissus (Virginia Creeper), requiring no support whilst others need to be tied to a structure. Climbers may be deciduous or evergreen.
Deciduous grape vine over pergola at Children's Garden, Royal Botanic Gardens, Melbourne. Ornamental or edible grape vines are a lush green colour despite being water hardy and leaves turn a brilliant crimson hue in Autumn. Photo Edwina Richardson. |
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'Biowall' at Ecoliving Exhibition, North Watson. The climbers will eventually cover the west facing wall providing protection from the hot summer sun. Photo Edwina Richardson.
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Evergreen climbers can used on a western wall of a building to provide protection from excess heat. They are particularly useful where there is limited space and no room to plant trees. Deciduous climbers are favoured on north facing pergolas, for example Vitis (grape). They allow solar access in Winter and provide shade in Summer. Climbers may also be useful for screening fences and providing greenery in narrow spaces between houses and fences where there is not enough room for shrub beds.
Choosing Lawns and Lawn Alternatives
Traditionally lawns in Canberra have incorporated a mix of exotic grasses which required high levels of water, nutrients and resources to maintain their appearance. Native species like Microlaena stipoides and Danthonia offer an alternative to these more resource intensive turfs and require mowing around ten times per year. However these grasses are only suited to open spaces with low rates of wear and tear.
Planting Nature Strips
One of Canberra’s revered characteristics is its generous nature strips of street trees underplanted with grass. As water becomes increasingly scarce and expensive, the nature strip will undergo a changed appearance. Traditional lawns may be gradually replaced with low water use plants. Successful combinations include local native grasses and herbs, massed natives and exotics, or a mix of exotics and succulents.
Exotic grass removed and nature strip replanted with Brachyscome daisies, Correa 'Dusky Bells', Grevillea 'Forest Rambler', Philotheca myoporoides and Lomandra longifolia. Design by Landscape Architect, Edwina Richardson. Photo Edwina Richardson. |
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Succulents such as Aeonium 'Schwarzkopf' and hardy silver foliaged plants mulched with local scoria replace the lawn on this Melbourne nature strip. Photo Edwina Richardson. |
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Native grasses and forbs replace the conventional grass strip in this Hackett garden. Photo Edwina Richardson. |
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Native lawn of Microlaena stipoides. Design by Landscape Architect Jennie Curtis. Photo Jennie Curtis. |
If you are considering making changes to the nature strip you will require approval from the City Ranger's Office.
>> For more information - Nature Strips in Canberra brochure
References
Adams, Laurence (1990) Trees and shrubs of Black Mountain, Mt Ainslie and Mt Majura - a key based on vegetative characters. CSIRO:Canberra
Eddy, David; Mallinson, Dave; Rehwinkel, Rainer and Sharp, Sarah (1998) Grassland flora - a field guide for the southern tablelands (NSW & ACT).
Pryor and Banks (1991) Trees and shrubs of Canberra. Little Hills Press: NSW.
Society for Growing Australian Plants Canberra Region (2001) Australian plants for Canberra region gardens & other cool climate areas.
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