Flax-leaf broom (Genista linifolia)

Flax-leaf broom is an evergreen shrub. It is an aggressive invader of native vegetation areas in warm temperate southern Australia.

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How does this weed affect you?

Flax-leaf broom produces large amounts of seed and can tolerate a range of environmental conditions. It quickly forms dense thickets, particularly in areas that are disturbed or degraded. It is an invader of roadsides, pastures, forestry, drains and areas of high conservation value.

Flax-leaf broom is a nitrogen fixing plant, which increases the amount of nitrogen in the soil. This reduces the growth of native plants, allowing flax-leaved broom to out-compete native shrubs and ground flora, eventually altering the ecosystem.  It can change the landscape of native grasslands, bushlands and riparian areas. The invasion of flax-leaf broom can provide harbour for pest animals and reduce the food resources available for native fauna. 

Where is it found?

Native to the Mediterranean Islands, southern France, Spain, Algeria, Morocco and the Canary Islands. It is regarded as a weed in New Zealand and Morocco, and has naturalised in the Americas, South Africa and Asia.

Originally introduced to Australia in the mid 1800s. It was widely planted as an ornamental shrub and hedge plant. Flax-leaf broom has now naturalised in Western Australia, South Australia, Victoria and New South Wales.

In Victoria it is distributed throughout the Mornington and Bellarine Peninsula’s, the Latrobe Valley and parts of central and western Victoria. In Western Australia it is found predominantly in the south western corner of the state between Perth and Albany. In South Australia infestations are located at Clare, the Mount Lofty Ranges and Eyre Peninsula. Small infestations also occur in Tasmania.

Localised infestations of flax-leaf broom occur in the Blue Mountains, Riverina, Bega Valley and various locations in the south west slopes regions of NSW. Larger infestations occur around Sydney. 

How does it spread?

Flax-leaf broom reproduces from seed. Pods burst open in the heat of summer ejecting the seeds. While most seeds will fall within a metre from the parent plant, many can be scattered up to several metres away.

Most seed spread is by soil movement. It is possible that graders and other roadside machinery have been responsible for spreading flax-leaf broom along roadsides and into new areas. Animals may also contribute to dispersal.

Lifecycle

Plants begin to flower and produce seeds at two years of age. Seeds are hard coated and can survive for many years in the soil. While germination usually occurs annually, major germination and survival events can occur following fire or soil disturbance.

Flowers mainly emerge from late winter through to late spring (August to November). Seed pods develop and ripen throughout the summer, releasing seeds in the heat of summer. Seeds germinate in the following autumn and spring. Plants do most of their growing during the warmer months.

What does it look like?

An evergreen shrub growing to 3 m high.

Stems

  • consists of one main stem with many branches above
  • brownish-green in colour
  • ridged
  • covered in fine short ‘woolly’ grey hairs when young, becoming less hairy with age

Leaves

  • groups of 3 leaflets are arranged alternately along the branch
  • leaflets are narrow and slender with pointed ends
  • 10–25 mm long and 1–4 mm wide with rolled edges.
  • dark green in colour
  • under side is densely covered in fine hairs giving a silvery appearance

Flower

  • bright yellow
  • pea-like
  • 10–15 mm long
  • occur in clusters of 3–16 at the tips of branches

Pod

  • hairy
  • green when young, turning a brownish black when ripe
  • oval in shape
  • 10–30 mm long and about 5 mm wide
  • contain 2–3 seeds

Seed

  • rounded
  • olive green to brown in colour
  • 2–3 mm in diameter 

Habitat

Flax-leaf broom grows well in warm temperate climates with a preference for slightly acidic soils. It can invade a range of ecosystems but favours disturbed sites such as the edges of forests and bushlands, roadsides and railway embankments. In its native range it grows in woodlands and scrub habitats. 

Acknowledgements

Author: Rachele Osmond

Technical review: Michael Michelmore

References

Department of the Environment (2011) Weeds in Australia: Genista linifolia, Australian Government. Available at www.environment.gov.au

Cherry H (2011) Weed management guide–Brooms: Scotch (Cytisus scoparius), Montpellier (Genista monspessulana) and flax-leaf (Genista linifolia) brooms, Caring for out Country. Available at www.weeds.org.au/WoNS/brooms 

Gardiner C (2014). Genista linifolia L in PlantNET - The Plant Information Network System of The Royal Botanic Gardens and Domain Trust, Sydney, Australia. Available at http://plantnet.rbgsyd.nsw.gov.au

Hosking JR, Sainty GR, Jacobs SWL & Dellow JJ (in prep) The Australian WeedBOOK.

Michelmore M and Osmond R (2006) NSW DPI Primefact 255: Gorse and brooms. Available at:  www.dpi.nsw.gov.au/agriculture/pests-weeds/weeds/profiles/gorse

Victorian Department of Environment and Primary Industries (2014) Flax-leaved broom. Available at www.depi.vic.gov.au/agriculture-and-food/pests-diseases-and-weeds/weeds  

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Control

Preference for control should be given to young plants before they reach reproductive maturity. Different methods of control will be required depending where the infestation occurs – native vegetation, plantation or pasture. All infestations will require regular and repeated follow-up control for a number of years.

Mechanical removal

Small and young plants can be manually pulled from the ground. Best results are obtained when the ground is soft and the entire plant, including roots, can be removed.

Larger infestations with a large proportion of mature plants can be bulldozed. Stems need to be broken off as close to ground level as possible to shatter roots. If using this method, other methods including fire and herbicide treatments will need to be used. Large scale mechanical control causes soil disturbance and a mass germination from the soil seed bank is highly likely.

In accessible areas such as pastures and plantations, mulching can be used on large and non-seeding infestations. The layer of mulch can help to temporarily reduce seed germination and regrowth, assisting in follow-up control.

Fire

Fire should only be used as part of an integrated weed management plan. Fire does not always kill adult plants, which can re-sprout. Use fire in combination with mechanical control to remove the above ground biomass and stimulate germination of seeds in the soil bank. Follow-up control with herbicide will be necessary. Some seeds can still remain dormant following fire, so regular monitoring and follow-up control is required.

Use fire as a method of control with caution. Unless the resources are available for continuous follow-up treatments, do not use fire in the control program.

Always consult local fire authorities prior to using fire as a means of control.

Herbicides

Herbicide treatment can be very effective for control.  It can be used as an initial treatment and for follow-up treatments. The most appropriate application methods are foliar spray, cut stump, basal bark and stem injection. Herbicide treatment should be applied when the plants are actively growing for the best results.

Young plants are particularly susceptible to herbicides and should be treated before their first flowering season. On larger, mature plants, all methods of herbicide application are effective, but will still required follow-up control.  Stem treatments of mature plants provides more targeted control and minimises off-target damage.

Biological control

There is currently no biological control agent available for the control of flax-leaf broom.

Herbicide options

Contact your local council weeds officer for control advice for Flax-leaf broom (Genista linifolia).

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Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area Duty
All of NSW General Biosecurity Duty
All plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.
All of NSW Prohibition on dealings
Must not be imported into the State or sold
Murray Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant. Notify local control authority if found.
South East
Exclusion zone: whole region except for the core infestation areas of Wollongong, Shellharbour, Kiama, Shoalhaven and Eurobodalla councils
Regional Recommended Measure*
Whole region: Land managers should mitigate the risk of new weeds being introduced to their land. Plant should not be bought, sold, grown, carried or released into the environment. Exclusion zone: The plant should be eradicated from the land and the land kept free of the plant.
*To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfill the general biosecurity duty for this weed click here

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For technical advice and assistance with identification please contact your local council weeds officer.
For further information call the NSW Invasive Plants and Animals Enquiry Line on 1800 680 244 or send an email to weeds@dpi.nsw.gov.au

Reviewed 2017