What is an environmental weed?

Unfortunately, some plant species that have been introduced to the Blue Mountains, either from other regions of Australia or from overseas, have developed into environmental weeds.

Why should we be concerned about environmental weeds?

• Environmental weeds spread rapidly. They degrade and in many cases totally displace locally indigenous vegetation communities (the local or native vegetation that occurs naturally in the Blue Mountains). Unique rainforests, eucalypt forests, woodlands, riparian (or stream) zones and peat swamps are all vulnerable. For example, introduced vines such as Japanese Honeysuckle and Jasmine are capable of completely smothering trees, shrubs, ferns and ground-layer plants. Local vegetation communities have been replaced by weed monocultures comprised of introduced species like Privet, Holly and Blackberry.
• Environmental weeds negatively affect indigenous wildlife. For example, the dense, ground-layer thickets of stems and leaves created by English ivy, referred to as ivy deserts by ecologists, smother existing plant species and completely cover all soil. When this occurs, lyrebirds, bandicoots and other ground feeding animals are unable to obtain nourishment. The habitat of threatened species, Blue Mountains Water Skink (Eulamprus leuraensis), has been invaded by weeds such as Tutsan and Japanese Honeysuckle.
• Environmental weeds pose a long-term, serious threat to the health and ecological integrity of Blue Mountains National Park and the Greater Blue Mountains World Heritage Area (GBMWHA).

Why do some introduced plant species become environmental weeds?

• There are plant species introduced to the Mountains that have no local competitors, such as other plant species, herbivores or insects, and so grow and spread vigorously.
• One or more local environmental conditions may particularly suit certain introduced species, allowing them to thrive e.g. high rainfall, mild temperatures, nutrient enrichment, favourable soil quality.
• Introduced plant species that reproduce prolifically and/or have vigorous growth rates particularly have potential to develop into environmental weeds.

Locally indigenous vegetation communities that have been disturbed, for example by clearing or infrastructure development, are especially susceptible to weed infestation.

Urban gardens are a major source of environmental weeds in Australia (Gallagher, Leishman 2014).

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How are weeds spread?

Plant seed can be widely distributed by wind, water, humans and other animals, particularly birds. For example, the seed of Buddleia davidii (Butterfly Bush) is widely dispersed by wind, and this plant regularly infests Blue Mountains National Park and the GBMWHA. The seed of environmental weeds like Holly, Privet and Arum lily can be distributed long distances by birds. Plant fragments may be swept down streams during heavy periods of rain, and become established as viable plants in Blue Mountains National Park. Trad (Tradescantia fluminensis) is often spread in this way.

There are plant species, such as bamboo, that spread rapidly via underground stems (rhizomes).

Also, the broken branches of certain plant species, such as willows, can establish roots and become viable plants when soil is moist.

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The social and economic costs of weeds

Environmental weeds can seriously disrupt the amenity of residents and communities, as happened when Prickly pear infested eastern Australia for many decades. In the Blue Mountains, environmental weeds such as Blackberry, Holly and Privet have been infesting public parks, scenic walks and lookouts, Blue Mountains National Park, and private gardens and property for many decades.

Weeds are expensive to control. Blue Mountains City Council (BMCC), the NSW National Parks and Wildlife Service (NPWS) and other government, non-government and industry entities annually expend considerable financial resources on the control of environmental weeds.

Environmental weeds destroy agricultural and other economic assets. The CSIRO estimates that weeds cost the Australian economy approximately five billion dollars per year.

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What can you do to help control environmental weeds?

• Please seriously consider removing all environmental weeds on your property, or as many as possible. For help with identifying and controlling environmental weeds, see the Environmental weeds of the Blue Mountains and Identification, illustrations and control of environmental weeds sections below.
• Where removal of all environmental weeds is not possible, keep in mind that regular removal of weed seed and/or regular pruning of weeds and their flowers can definitely be highly environmentally beneficial. Place weed seed in your BMCC green bin. Green waste can be placed in your green bin, or composted.
• Report environmental weeds to Blue Mountains City Council: by email at council@bmcc.nsw.gov.au or phone 47 80 5000.
• Avoid purchasing weed species and packets of weed seed from garden centres, markets or online. Avoid sharing weed species and weed seed with neighbours and friends.
• Before employing landscapers or undertaking any landscaping work on your property, consult the Environmental weeds of the Blue Mountains and Identification, illustrations and control sections below.

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Additional environmental weed control tips for gardeners

• As mentioned, for help with identifying and controlling environmental weeds, see the Environmental weeds of the Blue Mountains and Identification, illustrations and control of environmental weeds sections below.
• Be aware that Australian plant species not indigenous to the Blue Mountains but planted here have turned feral, including Kangaroo Paw and Bluebell creeper from West Australia. Introduced Wattles (Acacia spp.) are another common coloniser.
• Please do not dispose of garden waste, including lawn clippings, near or in bushland. Place all green waste in your BMCC green bin, or compost heap.
• Regularly observe how introduced species are behaving in your garden. Plants that spread rapidly, for example by suckering, or produce numerous seedlings are a concern. Consider removing these plants, especially if they are becoming established in adjacent bushland.
• As discussed, birds particularly consume, transport and deposit plant seed. Many major environmental weeds, such as Holly, Cotoneaster, Ivy and various lilies are distributed in this way. Monitor for unwelcome seedling development in your garden and nearby local bushland.

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Plant selection advice for gardeners

• Consider planting locally indigenous species on your property i.e. the native plants that occur naturally in your locality. Locally indigenous plant species can be purchased from the Conservation Society Nursery (https://bluemountains.org.au/nursery.shtml), Wildplant Rescue and Native Plant Nursery, Katoomba (https://www.wildplantrescue.org.au/) and Glenbrook Native Plant Reserve and Nursery (https://austplants.com.au/Blue-Mountains-Glenbrook-Reserve).
• Create an environmentally friendly garden! For advice on how to do this, see the BMCS webpage, Creating an Environmentally Friendly Garden in the Blue Mountains, at https://bluemountains.org.au/environmentally-friendly-garden.shtml.
• Consider joining a bushcare group, and help to restore wildlife habitat and degraded ecosystems. Participating in bushcare is a great way to learn about local nature. For further information see https://bluemountains.org.au/bushcare.shtml.
• When choosing garden plants that are not native to the Blue Mountains (also referred to as introduced or exotic plants), consult the Australian organisation, Gardening Responsibly. This organisation has conducted extensive research into the weed potential of numerous garden plant species. Check the weed potential of your garden plants and any proposed plant purchases at https://www.gardeningresponsibly.org.au/check-your-choice/. The website also offers lots of non-weedy garden species to choose from!
• BMCC implements a Blue Mountains Bushland Nursery Incentive program. Blue Mountains nurseries that do not stock or sell priority environmental weeds are accredited by BMCC. Please consider purchasing all exotic garden plants at accredited nurseries only. See https://www.bmcc.nsw.gov.au/bushland-nursery for a list of BMCC accredited nurseries.
• Remember, some types of locally indigenous and introduced plants can be highly flammable e.g. eucalypts, pines, conifers. If you live in a bushfire prone area, avoid planting immediately adjacent to or close to your home. Consider consulting the NSW Rural Fire Service and its home management advice (https://www.rfs.nsw.gov.au/). Purchasing water tanks and pumps may be a good idea.

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Common environmental weeds of the Blue Mountains

Check your property for these common weeds:

Agapanthus, Arum/Calla lily, Asparagus fern, Bamboo rhizomatous species, Blackberry, Blue periwinkle, Broom species, Butterfly-bush or Buddleia tree, Cassia, Cherry laurel, Cootamundra wattle, Cotoneaster species, Crofton weed, Day lily, English ivy, Evergreen Dogwood, Ginger lily, Gorse, Himalayan honeysuckle, Holly, Jasmine (White), Japanese honeysuckle, Lantana, Madeira vine, Montbretia, Pampas grass, Small-leaved and broad-leaved Privet, Red Hot Poker, Seaside daisy, Spanish heath, Tutsan, Trad/Tradescantia fluminensis, Watsonia, Willow (Grey Sallow).

Removal of these common environmental weeds from your garden/property, or even effective management of their flowers and seeds, could greatly benefit the natural environment of the Blue Mountains, especially if you live near a stream, swamp, bushland reserve or Blue Mountains National Park.

As mentioned, for help with identifying and controlling environmental weeds, see the Environmental weeds of the Blue Mountains and Identification, illustrations and control of environmental weeds sections below.

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The complete BMCC Blue Mountains noxious and environmental weeds list

Blue Mountains City Council maintains a comprehensive Blue Mountains environmental weed species list. All Blue Mountains environmental weeds are listed. The list was published in BMCC Development Control Plan 2015: Part C Environmental Management, Revision: Amendment 5 (April 2023).

A copy of this list can be found here: BMCC DCP 2015 Weeds List.pdf - please feel free to share it with friends and family.

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Identification, illustrations and control of environmental weeds

Two major challenges associated with controlling environmental weeds are:

• accurate identification, and
• effective implementation of approved control measures.

To assist with these two issues, here are some helpful resources.

For colour weed illustrations, management techniques and garden management advice, consult these BMCC resources: Weeds Information Booklet 2024 and https://weedsbluemountains.org.au.

Weeds Australia (https://weeds.org.au) also provides good advice and illustrations.

Do you need additional identification or management advice? Contact Blue Mountains City Council by email at council@bmcc.nsw.gov.au or phone on 47 80 5000. BMCC Bushcare Officers are available to help with identification and control advice.

The Society’s Bushcare Officer may be able to help with plant identification and advice on weed control (https://bluemountains.org.au/office-holders.shtml).

Professional arborists, bush regenerators and horticulturalists may also be able to offer advice with plant identification and management. They may charge a fee.

Always consult Blue Mountains City Council before undertaking tree management works or major landscaping on your property.

Thank you for considering the environmental weed management advice offered by the Society. Please note that Blue Mountains Conservation Society is a volunteer environmental organisation. Members of the Management Committee are volunteers and do not claim to offer professional standard advice. If in doubt about your particular matter of concern, please seek professional advice.

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References:
BMCC (2024) Bushland management Weed management Blue Mountains City Council https://www.bmcc.nsw.gov.au/weeds

BMCC (n.d.) Weeds of the Blue Mountains Cherishing our bushland Blue Mountains City Council https://weedsbluemountains.org.au/

CSIRO (n.d.) Biological control of weeds https://www.csiro.au/en/research/plants/water-marine/weed-biocontrol

Duursma, D.E., Gallagher, R.V., Roger, E., Hughes, L., Downey, P.O., Leishman, M.R. (2013) Next-Generation Invaders? Hotspots for Naturalised Sleeper Weeds in Australia under Future Climates. PLOS ONE 8:12 DOI: 0.1371/journal.pone.0084222

Environment and Heritage (2024) Weeds Find out how weeds threaten biodiversity and what we are doing about it Department of Environment and Heritage NSW Government https://www2.environment.nsw.gov.au/topics/animals-and-plants/pest-animals-and-weeds/weeds

Gallagher, R., Leishman, M. (2014) Invasive plants and invaded ecosystems in Australia: implications for biodiversity Chapter 6 in Stow, A., Maclean, N., Holwell, G. (eds.) Austral Ark: The State of Wildlife in Australia and New Zealand Cambridge University Press

Groves, R.H., Boden, R., Lonsdale, W.M. (2005) Jumping the Garden Fence: Invasive garden plants in Australia and their environmental and agricultural impacts CSIRO World Wildlife Fund https://wildlife.lowecol.com.au/wp-content/uploads/sites/25/Jumping-The-Garden-Fence.pdf

Hulme, P.E., Brundu, G., Carboni, M., Dehnen-Schmutz, K., Dullinger, S., Early, R., Essl, F., González-Moreno, P., Groom, Q., Kueffer, C., Kühn, I., Maurel, N., Novoa, A., Pergl, J., Pyšek, P., Seebens, H., Tanner, R., Touza, J. van Kleunen, M., Verbrugge, L. (2018) Integrating invasive species policies across ornamental horticulture supply chains to prevent plant invasions Journal Applied Ecology 55:92–98. DOI: 10.1111/1365-2664.12953

Maher, J., Stringham, O.C., Moncayo, S., Wood, L., Lassaline, C.R., Virtue, J., Cassey, P. (2023) Weed wide web: characterising illegal online trade of invasive plants in Australia. NeoBiota 87: 45–72. https://doi.org/10.3897/neobiota.87.104472

Smith, P., Smith, J. (2010) Urban edge effects in the Blue Mountains, New South Wales: implications for design of buffers to protect significant habitats PACIFIC CONSERVATION BIOLOGY 16: 92–100. Surrey Beatty & Sons, Sydney https://bluemountains.org.au/documents/research/blue-mountains-urban-edge-effects.pdf

Strelau, M., Clements, D.R., Benner, J., Prasad R. (2018) The Biology of Canadian Weeds: 157. Hedera helix L. and Hedera hibernica (G. Kirchn.) Bean Canadian Journal of Plant Science 98: 1005–1022 (2018) dx.doi.org/10.1139/cjps-2018-0009