Encouraging & facilitating native vegetation establishment and biodiversity in the Border Rivers region
This information is based on “Getting Started: An Introduction To Growing & Propagating Australian Native Plants”, Australian Plants Society NSW
With their enormous variety, native plants give great pleasure to Australians and our overseas visitors. They occur over many climatic zones and in a range of habitats. Belonging to many different plant families, they are not homogeneous as are roses. A bottlebrush will not have the same growing needs as a eucalypt.
Australian plants are found in deserts, wetlands, rainforests and mountains, in soils ranging from rich to very poor. They all have individual needs. If an arid region plant and a rainforest plant are watered equally, one may get enough and the other too little. However, plants can still survive in conditions different to their natural habitat if well-informed decisions are made.
The critical question is:
“Will this plant grow in my climate and soils?”
A sound choice is plants that are native to your local area. Select ones that have been propagated from seed or cuttings collected locally. Plants of the same species can have slightly different genetic composition in each of the localities in which they occur.
Exploring the plants in this Botanic Garden, or your own local one if you are a visitor, is a good way to start. Here the plants are all native to the Upper Darling Basin. You can see what they look like and how well they are suited to the conditions. You can also observe how they have been established: mounding, mulching, staking, protection etc. This information is available on our website, www.goondiwindibotanicgarden.org.
Most garden centres stock a range of common native species and cultivars. It can be worth visiting specialist nurseries, including community nurseries, for a wider range and expert advice.
If you are keen, you can propagate your own plants from seed, cuttings or division. This can be quite challenging, and some research prior to starting is always worthwhile.
No single set of soil conditions suits all Australian native plants. Some will grow in clay and others in sand. The most important single factor is that, for most, the soil MUST be well drained, especially in the top 30 cm. The further the water soaks into the subsoil the better. Some species, for example creek wilga, river cooba and some of the eucalypts do not need good drainage.
Planting mounds of 30 cm to 50 cm are ideal. Try to run excess surface water away to ponds or hollows. Deep ripping in heavy soils is recommended about two months prior to planting. This opens up the clay soil and allows roots to penetrate.
Soil improvement pays dividends. Light sandy soils benefit from up to 10% rotted organic matter. Gypsum and humus help to improve the texture of clay soils, but be sure to mix them in very thoroughly.
Prepare soil before planting and get rid of weeds. A useful method is to spread thick layers of newspaper and spray any weeds that still manage to get through. Mulch is important for moisture conservation, and it breaks down over time to form a light loam. Locally sourced mulch is usually the best type. Some mulches can affect the pH of soil adversely so advice should be sought.
Above all, concentrate on species that are suitable for your soil type and area.
Study the location carefully before you plant. Look for the sunny and shady areas, the damp areas and those that are exposed to wind or frost.
Make sure that roots are not pot bound – coiled into a tight mass. Prune them by cutting back the roots and combing them out if this occurs.
For plants and trees not affected by frosts, planting in autumn while the soil is still warm gives them eight or nine months to establish before the following summer. Make sure the soil is moist, and dig a hole slightly deeper and twice as wide as the pot. Fill it with water. After it has drained away, put one or two teaspoons of slow release fertiliser in the bottom of the hole and mix it with the natural soil.
Tap the pot to loosen the plant, turn upside down and let it slide into your hand. Lower it into the hole, spread loose soil around it and firm it down with your fingers. Keep filling so that the final soil level is at the same level as the top of the potting mix. Rotting may occur if soil covers the stem.
Keep the soil moist, but not soggy, for the first week or so. This will give the disturbed roots time to recover. Remove any plastic ties that may be round the trunk as failure to do so can result in ringbarking.
In an exposed, windy position, put two stakes in before planting. Use soft material such as hessian strips to tie a figure 8. This allows the plant some movement while it develops a strong root system bur avoids over-dependence on the stakes. They should be removed when the plant is established.
Even for species that are frost hardy when older, some frost protection during the first winter may be required. A good way is to surround with hessian, leaving the top open, and this can stay all winter.
During their first months, native plants need water during hot, dry periods. After that, if there is reliable summer rainfall, this will suffice. However, water is still required during long, dry spells. Water-stressed plants flower very poorly or not at all.
Drippers or micro-sprays apply water precisely where it is needed. For hand watering, a good occasional soaking is much better than frequent light sprays, which only encourage the growth of shallow roots that are susceptible to heat damage. Mulching around plants is an excellent way to conserve water and keep roots cool. Keep mulch away from stems to avoid fungal attack.
Ideally, once established, plants should be given the same conditions as they have in nature. If local plants are used, the only watering they should need after the first year is during extended dry periods. If you are growing plants from other climatic regions, get to know when they are showing signs of distress. Hollows and ponds in the garden store stormwater and slowly release it to the soil.
Always water thoroughly, and do so in the early morning or late afternoon. Drip irrigation is better than sprinklers. Not only does this save water by applying it where it is needed, but it also cuts down on weed growth.
All plants need nutrients for healthy growth – it is a misconception that natives shouldn’t be fertilised. However, many species are native to poor soils and have become very efficient at extracting nutrients. Added fertiliser can lead to nutrient take-up in excessive amounts, with disastrous consequences.
A good practice is to use a slow release (8 – 9 month) fertiliser during the growing season. Special low-phosphorus slow release fertilisers are also available. All fertilisers should be used sparingly – any excess is wasted and can end up in rivers and streams.
Australian native plants are subject to a wide range of pests. There are three main groups: chewers, suckers and rotters.
Chewers are the larvae of beetles, moths, butterflies and other insects. In a mature garden they are usually controlled by a wide range of birds. However, a severe infestation of caterpillars can cause serious damage to individual plants. Physical removal is the best response. A strong jet of water usually works, or you can flick them off with a gloved hand. For bigger plants, a relatively safe insecticide (pyrethrin based) can be used.
Borers can usually be killed by inserting a piece of wire into their hole. They tend to attack plants that are not suited to the conditions.
The most common suckers are aphids and scale. They affect the vigour of plants and make them susceptible to other pests and diseases. Aphids can often be removed with a strong jet of water, but a pyrethrin spray may be needed. Scale can be scraped off or treated with white oil.
Rotting is caused by fungi. It is usually impractical to treat root rot: remove the stumps and roots of dead plants, and improve garden drainage. Collar rot is controlled by ensuring that mulch and moist organic material is kept away from stems.
There are many other pests. Taking expert advice is usually the best way to deal with them.
Some native plants respond to pruning just like other plants. If you want them to be bushy, annual pruning encourages branching. Even better, regular tip pruning (pinching off the end few millimetres) during the growing season gives excellent result.
Callistemons (bottlebrushes) benefit from having the dead flowers cut off as soon as flowering finishes. This produces more flowering stems in the next season. Some plants will tolerate being cut back by about a third, and some will regrow after cutting back to ground level. However, it is important before pruning a particular species to get advice. Some plants definitely resent pruning.