Weeds

A weed is a plant that is not wanted, is out of place, is self sown and usually growing out of control. Weeds can be spread in many ways, including by birds that feed on them and by escaping from suburban gardens. Find out how you can help to reduce weeds in and out of your backyard.

What is the difference between an environmental weed and a noxious weed?

• An environmental weed is often a garden escapee i.e. it was originally grown in someone's garden, but has escaped into other areas. They are invasive plants which are adaptable and opportunistic. It is preferable to remove them altogether or at least keep them under control.
• A noxious weed is a plant that legally must be removed and/or controlled. Most noxious weeds provide a threat to human health, the environment, livestock or the agricultural industry.

Why are weeds a problem?

All weeds inhibit the growth of more desirable plants in one way or another.
Weeds aren't necessarily 'bad plants' they are just in the wrong place.

Can native plants be weeds?

Many Australian natives grown outside their indigenous (naturally occurring) area, can become weeds when grown in other areas of Australia. An example is the Cootamundra Wattle which has become a weed in the Sydney area.

Complex bird-weed relationships

Birds can contribute to the spread of weeds. Many birds eat berries and seeds, which do not break down in their gut, but pass through and are distributed in their droppings. Many plants rely on birds for seed dispersal, including many weeds. Examples of weeds distributed by birds in the Sydney area are Privet, Ochna and Asparagus Fern. The best way to prevent this is not to grow these types of plant and to remove any that you already have.

In addition to providing a food source, an even greater number of weeds are used by birds for shelter and nest sites. Many small birds, such as Superb Fairy-wrens, Eastern Spinebills and White-browed Scrubwrens, use woody weeds such as lantana, primarily for shelter and nesting, but some also feed on the flowers and seeds as well as the insects that live in it. Thickets of Lantana and other dense weedy shrubs such as raspberry (Rubus spp.) are also a preferred habitat of Australian Brush-turkey chicks and therefore impacts upon their dispersal and survival by providing them with shelter. Using large-scale techniques (such as fire or slashing) to remove all woody weeds like Lantana from a site is therefore likely to cause serious disturbance to the existing bird community and may result in these birds being lost permanently from the site. While many weeds should be removed, we advocate a long-term and cautious approach to doing this, with a staged replacement of the weed species to try to minimise the impact on the bird community.

The type of weed removal necessary is highly dependant on the particular species involved and there is an abundance of advice available online on the best ways for controlling and eradicating specific species (see http://www.weeds.crc.org.au/index_flash.html and http://www.weeds.org.au/index.html). Generally a combination of techniques is needed to effectively control or remove the infestation and monitoring should be ongoing to ensure that any changes to the site and the effectiveness of the techniques used can be documented.

Whenever weed removal is deemed necessary, to minimise the impact on the birds utilising them, we suggest that only small patches be treated at a time. By leaving patches of weeds untreated, birds and other fauna have areas of refuge to avoid the disturbance. If the option is available, it is also better to remove weeds outside the peak bird breeding season which, for most birds, is between July and January/February. Removal should begin in the areas with the greatest proportion of native vegetation (and presumably lightest weed infestation) and work towards the heaviest infestation. This not only allows valuable bird habitat to remain but also reduces the chances of reinfestation of the weeds and allows natives to regenerate.

What should you do?

• Grow plants that are indigenous to your local area or which are non-invasive and will not 'escape' outside your garden.
• Watch to see what birds, if any are using the weed-infested area.
• Remove weeds as soon as they emerge.
• Remove establised weeds slowly and in small patches and replace the weeds with an equivalent native plant where possible (e.g. something that provides dense cover). Allow new plantings to establish before moving on to the next patch.
• Never dispose of garden refuse in bushland or wasteland areas. This is the most frequent cause of garden escapees.
• Composting garden refuse should help, except for persistent weeds such as onion weed, whose corms (bulb-like stem bases) can take years to die. These weeds should be bagged and disposed of in your garbage.
• Consult your local council for more advice on how to control the weeds found in your area.