Scotch broom (Cytisus scoparius subsp. scoparius)

Also known as: English broom

Profile

Impact

Scotch broom will smother desirable vegetation which reduces pasture stocking rates. They form dense thickets which can block access by humans and stock but harbour feral animals such as rabbits, foxes and pigs.

Toxicity

Scotch broom is toxic to humans and will cause discomfort and irritation, but is not life-threatening. The seeds and leaves are poisonous and can cause high blood pressure and nausea if ingested. If ingested in large amounts the toxins contained in scotch broom can weaken the heart. 

What to do if poisoning occurs:

  • If the patient is unconscious, unresponsive or having difficulty breathing dial 000 or get to the emergency section of a hospital immediately.
  • If the patient is conscious and responsive call the Poisons Information Centre on 13 11 26 or your doctor.
  • If going to a hospital take a piece of the plant for identification.

Distribution

Gorse and brooms are mostly confined to cool temperate areas of NSW, particularly the tablelands. Gorse is a problem in the south-eastern region of the state and the Blue Mountains. Some large populations of Scotch broom exist on the Barrington Tops and near Braidwood.

Distribution map

Spread

Originally, both gorse and brooms were planted as hedge or ornamental garden plants. Their main method of spread is now via seed by soil, water, machinery, footwear, stock and wildlife. The ability of the plants to shoot their seeds some metres away allows infestations to thicken quickly and to spread, particularly along water courses. Their pods burst open in hot weather during spring and summer, scattering seeds up to several metres from the plant. Seeds of these species have a hard coat that can delay germination for months or years, allowing large seed banks to develop. Seed can remain viable in the soil for many years.

Plants are normally at least two years of age before they are able to reproduce. Flowering mostly occurs from late winter to late spring. A second flowering may occur towards the end of summer and into autumn. Occasional flowers may be seen at other times.

Although germination and seedling establishment do occur annually, it is common for significant germination and survival events to occur in years following fire or soil disturbance.

Description

Scotch broom is an upright, evergreen shrub that grows to 4 m high but more commonly 1–2 m high. There are other species in this family that are similar in appearance and can be difficult to tell apart from the species covered here, such as flax-leaf broom (Genista linifolia) and Madeira broom (Genista stenopetala). Hybrids between the different species may also exist. Brooms are characterised by a long seed life, seedlings that take two or more years to grow to seed producing shrubs, and adult shrubs that may live for several decades. 

Its upper stems usually with five pronounced ridges and woody with numerous branches.

Leaves are shortly stalked, softly hairy with three leaflets per leaf. The middle leaflet is up to 20 mm long, other leaves are somewhat shorter. 

The flowers are yellow and pea-like. They are 2 – 2.5 cm long, occuring singly or in pairs, 

Brown to black pea-like pods have hairs that are confined to margins. Each pod is up to 7 cm long and 1.3 cm wide, it contains 5 - 22 seeds.

The seeds are yellowish-brown in colour to olive green. Oval shaped up to 4 mm long. They are smooth, rounded and slightly flattened.

Habitat

Scotch brooms often become dense on river banks, forest margins, roadsides and other disturbed areas. They will also invade pastures and native vegetation. They are able to grow on a wide range of soil types and are able to flourish in areas with an annual rainfall over 500mm.

Acknowledgements

Authors: Michael Michelmore, Regional Weed Control Coordinator, Goulburn
Rachele Osmond, former Weeds Project Officer, Tamworth

The authors wish to thank the following people for their valuable input and comments. Annie Johnson; Stephen Johnson; John Hosking, NSW DPI and Jonah Gouldthorpe and Sandy Leighton Tasmania DPIW.

References

National Gorse Taskforce (2006) Gorse national best practice manual. Managing gorse (Ulex europaeus L.) in Australia. Department of Primary industries and Water, new Town, Tasmania.

CRC for australian Weed Management (2004) Weed Management Guide: Gorse (Ulex eurpaeus).

CRC for australian Weed Management (2004) Weed Management Guide: White Spanish broom (Cytisus multiflorus).

CRC for australian Weed Management (2004) Weed Management Guide: White weeping broom (Retama raetam).

Hosking, JR, Smith, JMB and Sheppard, AW (1998) Cytisus scoparius (L) Link ssp. scoparius. in, The Biology of Australian Weeds, volume 2. eds FD Panetta, RH Groves and RCH Shepherd. RG and FJ Richardson, Melbourne. pp. 77-88.

Richardson, RG and Hill, RL (1998) Ulex europaeus L. in The Biology of Australian Weeds, volume 2. eds FD Panetta, RH Groves and RCH Shepherd. RG and FJ richardson: Melbourne. Pp. 269–290.

Parsons, WT and Cuthbertson EG (2001) Noxious Weeds of Australia. Inkata Press. pp. 467-484.

Other publications

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Control

The control and management for gorse and brooms are similar. Management needs to address:

  • Movement of seed so that new patches do not establish.
  • The protection of humans and animals from damage from gorse prickles.
  • The removal of sticks and stumps to allow area to be trafficable.
  • Regrowth so that the plants do not re-establish.
  • Seedlings so that gorse and brooms do not re-establish over time.
  • Long term landuse to prevent reinfestation.

Techniques for control include fire, mechanical removal, grazing, herbicides, property hygiene and biological control. The cost of control is typically high. 

New infestations should be treated prior to plants flowering. Once plants begin to seed they are much more difficult to control and spread into other areas is more likely. While isolated patches may not seem a priority for some, they are more cost effective to control than larger patches. Any infestations left uncontrolled can lead to a rapid spread and increase in the problem. Tackle small, outlying infestations first and coordinate control with neighbours. Once established, these weeds are very difficult to eradicate. Control programs need a minimum of five years commitment, including yearly inspections to check for regeneration and regrowth, and follow-up treatment.

Integrated management

Integrated management programs are essential for long-term control. This involves using a combination of control methods to get the best possible results. Repeated removal of above-ground growth, by slashing, grazing or fire, will suppress plants but will not destroy them. Treatments that shatter the roots or herbicides that move though the plant and roots are required to kill these weeds.

Fire

Adult plants are typically not killed by burning. Fire kills above ground parts of the plant but plants regrow from the root stump. Also, fire does not kill the numerous seeds buried in the soil profile. Fire stimulates seed germination. Therefore any treatment using fire must be followed up with other treatments such as herbicide for at least five years.

These shrubs, particularly gorse, produce intense heat and flames when burnt, even in winter. There are large risks associated with the use of fire, including injury to people, property, and desirable plants and fauna. Fire can only be considered if these risks have been fully managed.

Mechanical

Hand grubbing

Plants must be removed well below the soil surface. This means of control is only appropriate for small scattered plants and seedlings and only when the ground is soft.

Mechanical slashing and grubbing

The stems of these shrubs are tough. Specialist equipment is generally used to break stems, to allow further access, and to avoid puncturing tyres. Mechanical treatments that go into the ground to shatter roots are considerably more successful than top removal treatments. The extra costs to get the job done properly are worth it. Mulchers are available that break sticks to fragments and shatter roots. Since slashers and choppers do not shatter roots, plants treated by these means will almost certainly need follow-up treatment. For long-term control, mechanical clearing should be used in combination with pasture establishment to provide competition, grazing, and herbicide treatments.

Grazing

Both sheep and goats will eat gorse and broom seedlings. Sheep will generally suppress the regrowth of gorse and broom but will have little impact on adult plants. Large numbers of goats can be used to reduce the regrowth of adult gorse and brooms. Grazing is also done in combination with burning, however sheep fleece may continue to be contaminated by charcoal for years after fire.

Property hygiene

Property hygiene is important to reduce the spread of weeds. As gorse and broom seed is easily transported in mud, thoroughly check equipment, footwear, vehicles and animals for seed and wash down before leaving infested areas. Vehicles, bush walkers and horse riders should stay on tracks to reduce the amount of seed picked up on tyres, footwear and hooves.

Biological

Biological control agents for gorse and brooms that have been trialled and released in NSW include a gall mite (Aceria genistae), a moth (Leucoptera spartifoliella), a psyllid (Arytainilla spartiophila), a seed beetle (Bruchidis villosus) and a rust fungus (Uromyces genistae-tinctoriae). With the exception of the gall mite (which is capable of significant damage but not yet released), these agents are all well established. However, results have been variable with no agent having any significant impact on gorse or brooms over large areas.

Herbicide

Herbicides are useful for both initial treatment and for treatment following other control methods. When using herbicides, it is important to follow the label recommendations. Herbicide control of gorse and broom frequently requires more than one treatment to be effective. The most appropriate applications are either foliar spray or cut stump methods. When applying foliar sprays ensure that the mixture is applied to the point of run-off over the whole plant, and use a penetrant or surfactant as directed on the herbicide label. Chemicals registered for the control of noxious weeds are listed in the publication Noxious and Environmental Weed Control Handbook. For further information on chemicals and rates, read the product label or enquire at your herbicide reseller.

Herbicide options

WARNING - ALWAYS READ THE LABEL
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au

See Using herbicides for more information.


Glyphosate 360 g/L (Roundup®)
Rate: 100–130 mL per 10 L of water
Comments: Foliar spot spray application.
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate


Picloram 100 g/L + Triclopyr 300 g/L + Aminopyralid 8 g/L (Grazon Extra®)
Rate: 250 or 350 mL in 100 L of water
Comments: Lower rate when actively growing mid-summer to pod formation. Higher rate for autumn-winter treatment.
Withholding period: Where product is used to control woody weeds in pastures there is a restriction of 12 weeks for use of treated pastures for making hay and silage; using hay or other plant material for compost, mulch or mushroom substrate; or using animal waste from animals grazing on treated pastures for compost, mulching, or spreading on pasture/crops.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


Picloram 44.7 g/kg + Aminopyralid 4.47 g/L (Vigilant II ®)
Rate: Undiluted
Comments: Cut stump/stem injection application. Apply a 3–5 mm layer of gel for stems less than 20 mm. Apply 5 mm layer on stems above 20 mm .
Withholding period: Nil.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


Triclopyr 300 g/L + Picloram 100 g/L (Grazon® DS)
Rate: 250 or 350 mL per 100 L of water
Comments: Lower rate when actively growing mid-summer to pod formation. Higher rate for autumn-winter treatment.
Withholding period: Nil.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


Triclopyr 600 g/L (Garlon® 600)
Rate: 170 mL per 100 L of water
Comments: Late spring to early autumn. Actively growing bushes.
Withholding period: Nil.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


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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 Mandatory Measure
Must not be imported into the State or sold
Central Tablelands Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. Land managers should mitigate spread from their land.
Protect conservation and natural environments that are free of Scotch broom
Greater Sydney Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land.
Hunter
Exclusion zone: whole region except for the core infestation area of the Upper Hunter (Barrington Tops)
Regional Recommended Measure*
Whole region: The 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. Land managers should mitigate the risk of the plant being introduced to their land. Core infestation area: Land managers should mitigate spread from their land.
Murray
Snowy Valleys Council
Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. Land managers should mitigate spread from their land. Notify local control authority if found.
Murray
Whole region excluding Snowy Valleys Council.
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.
North Coast 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.
North West
An exclusion zone is established for all lands in the region, except the core infestation area comprising all Local Government Areas east of the Newell Highway
Regional Recommended Measure*
Whole of region: The plant should not be bought, sold, grown, carried or released into the environment. Exclusion zone: Land managers should mitigate the risk of new weeds being introduced to their land; land managers should mitigate spread from their land; the plant should be eradicated from the land and the land kept free of the plant. Core infestation: Land managers reduce impacts from the plant on priority assets
Northern Tablelands Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. Land managers should mitigate spread from their land. The plant should not be bought, sold, grown, carried or released into the environment. Notify local control authority if found.
Riverina
Whole region excluding Snowy Valleys Council
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.
Riverina
Snowy Valleys Council.
Regional Recommended Measure*
Land managers should mitigate the risk of new weeds being introduced to their land. Land managers should mitigate spread from their land.
South East
Core infestation area: whole region except exclusion zone of : Bega council
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