Mysore thorn (Caesalpinia decapetala)

Mysore thorn, also known as wait-a-while, is an aggressive prickly shrub that forms dense thickets. It invades environmental areas, creek banks, roadsides, pastures and bushland.

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How does this weed affect you?

Mysore thorn was originally planted in gardens as a hedge plant. It is now an environmental weed. Mysore thorn can affect the biodiversity of native bushland areas by out-competing and smothering native species. Its dense thickets can provide a harbour for feral animals, restrict the habitat available for native animals and inhibit access to water, roads and pasture.  Invasion and establishment of exotic vines and scramblers has been identified as a key threatening process for many vulnerable and endangered species in NSW. Mysore thorn is one of the main species listed as a threat.

What does it look like?

Mysore Thorn is a large evergreen shrub growing 2–4 m high, or up to 20 m high when climbing over supporting vegetation.

Branches

• covered in fine golden hairs
• hooked thorns up to 5 mm long occur along its length
• bark is rough at the base, then smoother and cream-green above

Leaves

• dark green above and paler underneath
• bipinnate, consisting of a main stalk up to 30 cm long with 3–15 opposite pairs of pinnae
• each pinna has 3–12 pairs of oblong leaflets (10–22 mm long and 4–11 mm wide)

Flower

• pale yellow or whitish in colour
• 5 petals, 10–15 mm long and 8–15 mm wide
• on stalks 15–25 mm long
• arranged in spike-like clusters at the tip of branches, up to 35 cm long

Pod

• oblong, flat and hairy
• 6–10 cm long and 2–3 cm wide
• has a small projection (beak) at one end
• split open when mature
• contain 4–9 seeds

Seed

• black and brown in colour
• 6–10 mm wide

Where is it found?

Mysore thorn is native to Japan, China, India and Malaysia. It is present in many countries around the world and is an invasive weed in New Zealand, the Dominican Republic, South Africa and Hawaii.

Mysore thorn is predominantly located along the south-eastern Queensland coast. Scattered infestations occur in some southern inland locations and along most of Queenslands coast line.

In New South Wales many localised infestations—which continue to spread—occur in the north coast region. Small, localised infestations are also present along the central coast of NSW.

Maps and records

• Recorded presence of Mysore thorn during property inspections (Map: Biosecurity Information System - Weeds, 2017-2024)
  These records are made by authorised officers during property inspections under the Biosecurity Act 2015. Officers record the presence of priority weeds in their council area and provide this to the NSW Department of Primary Industries. Records reflect the presence of the weed on the date of inspection.
  
  

How does it spread?

Mysore thorn reproduces by seed, which may stay viable in the soil for up to 10 years. The seed is mainly dispersed by animals that feed on the fruit, such as rodents, birds and cattle. Seed pods float on water, spreading seeds downstream to new locations.

The branches of mysore thorn produce new roots when they come into contact with the ground, anchoring the plant into the soil. Plants will re-shoot vigorously when cut.

Lifecycle

Mysore thorn flowers during winter and spring. Fruits are produced from August through to December. 

What type of environment does it grow in?

Mysore thorn prefers humid coastal conditions in sub-tropical to tropical climates. Mysore thorn grows on a variety of soil types and will tolerate annual rainfalls from 300 to 3000 mm. It will often grow in disturbed areas, roadsides, pastures, creek banks, native grasslands and along the edges of bushlands and forests.

References

CABI invasive species compendium online data sheet. Caesalpinia decapetala (Mysore thorn). CABI Publishing 2011. www.cabi.org/ISC. Accessed August 2014.

Department of the Environment (2011). Weeds in Australia: Caesalpinia decapetala . Australian Government. www.environment.gov.au/biodiversity/invasive/weeds/identification/index.html. Accessed August 2014. 

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

Parsons, W.T. & Cuthbertson, E.G. (2001). Noxious weeds of Australia, CSIRO Publishing, Collingwood.

Richardson F.J., Richardson R.G. & Shepherd R.C.H. (2011). Weeds of the south-east: an identification guide for Australia. RG and FJ Richardson, Meredith, Victoria.

More information

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Control

Any control activities for mysore thorn will need to be monitored and followed up with additional control measures as required.

Physical control

Only recommended for small plants and seedlings that can be manually pulled or hoed from the ground. Take care to remove all of the roots. Larger plants and infestations are difficult to treat in this way. The thorny habit of mysore thorn and ability to rapidly re-shoot from cut stems, makes mechanical control challenging.

Herbicide control

Treat when plants are actively growing and before flowering. In dense infestations, foliar applications repeated every 3–9 months will give the best results.

Herbicide options

See Using herbicides for more information.

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Metsulfuron-methyl 300 g/kg + Aminopyralid 375 g/kg (Various products)
Rate: 20 g per 100 L of water and a wetting agent at 100 mL/100 L.
Comments: Thorough spray all the foliage and stems until wet. Suitable wetting agents: BS1000 Biodegradable surfactant, Chemwet 1000 Wetting Agent, Uptake Spraying Oil or Pulse Penetrant
Withholding period: Pastures - Grazing for meat production or cutting for animal feed: Do not graze for 56 days after application. See label for further details
Herbicide group: 2 (previously group B), Inhibition of acetolactate and/or acetohydroxyacid synthase (ALS, AHAS inhibitors) + 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: High/Moderate

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Metsulfuron-methyl 600 g/kg (Various products)
Rate: 10 g per 100 L of water
Comments: Spray to thoroughly wet all foliage, but not to cause run off. Apply to actively growing plants before flowering. Add wetting agent.
Withholding period: Nil (recommended not to graze for 7 days before treatment and for 7 days after treatment to allow adequate chemical uptake in target weeds).
Herbicide group: 2 (previously group B), Inhibition of acetolactate and/or acetohydroxyacid synthase (ALS, AHAS inhibitors)
Resistance risk: High

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Picloram 44.7 g/L + Aminopyralid 4.47 g/L (Vigilant II ®)
Rate: Undiluted
Comments: Cut the stump then apply a 3–5 mm layer of gel for stems less than 20 mm diameter. Apply 5 mm layer on stems above 20 mm diameter .
Withholding period: Nil.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
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 pest 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.
Greater Sydney	Regional Recommended Measure* (for Regional Priority - Prevention) The plant should be eradicated from the land and the land kept free of the plant. The plant should not be bought, sold, grown, carried or released into the environment.
Hunter	Regional Recommended Measure* (for Regional Priority - Eradication) Notify local control authority if found. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant.
North Coast Exclusion (eradication) zone: Bellingen Shire LGA, Clarence Valley LGA, Lord Howe Island, Port Macquarie-Hastings LGA. Core infestation (containment) zone: Ballina Shire LGA, Byron Shire LGA, Clarence Valley LGA, Coffs Harbour City LGA, Kempsey Shire LGA, Kyogle Shire LGA, Lismore City LGA, Nambucca Valley LGA, Richmond Valley LGA, Tweed Shire LGA.	Regional Recommended Measure* (for Regional Priority - Containment) Whole of region: Land managers should mitigate the risk of the plant being introduced to their land. A person should not buy, sell, move, carry or release the plant into the environment. Exclusion zone: Notify local control authority if found. Land managers should eradicate the plant from the land and keep the land free of the plant. Core infestation: Land managers should mitigate spread of the plant from their land. Land managers should reduce the impact of the plant on assets of high economic, environmental and/or social value.
South East Containment zone: Wollongong Local Government Area. Exclusion zone: Whole of region except containment zone.	Regional Recommended Measure* (for Regional Priority - Containment) Whole of region: Land managers mitigate the risk of new weeds being introduced to their land. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Within exclusion zone: Land managers should eradicate the plant from the land and keep the land free of the plant. Notify local control authority if found. Within containment zone: Land managers should reduce the impact of the plant on assets of high economic, environmental and/or social value. Land managers should mitigate spread of the plant from their land.
	*To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfil the general biosecurity duty for this weed click here

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Reviewed 2023