Siratro (Macroptilium atropurpureum)

Siratro is a trailing herb. It is a weed of pasture and roadsides, north of Sydney.

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How does this weed affect you?

Siratro will smother native shrubs, grasses or younger trees. It can form dense infestations along forest edges. It is common around waterways, particularly in coastal sand dunes north of Sydney.

What does it look like?

Siratro is a climbing or creeping perennial legume with hairy stems that grow 2-3 m long. It flowers most of the year.

Leaves are:

dark green
divided into 3 leaflets, with the two lower leaflets slightly lobed
leaflets 2-7 cm long and 1.8-5 cm wide
slightly hairy on top, very hairy underneath
on stalks 2-4.5 cm long.

Flowers are:

pea-like
grouped in clusters of 6-12 individual flowers
in clusters around 40 cm long
dark reddish black to purple.

Fruit are:

hairy pods
5-10 cm long and 3-5 mm wide
turn from green to brown when old.

Seeds are:

light brown – black
oval or kidney-shaped
3 mm long.

Stems are:

creeping or climbing
2-3 m long
covered with short, soft hairs
woody at the bottom of older plants

Roots are:

deep with a swollen taproot.

Where is it found?

In NSW it is common around roadsides and waterways, particularly in coastal sand dunes north of Sydney. It is also found on Lord Howe and Norfolk Islands.

It is native to central and north America.

How does it spread?

Siratro is spread by seeds and plant parts. Seed pods burst open when ripe, shooting seeds several metres away. Seeds are also spread by water and cattle. The seeds are still viable after being eaten and then defecated whole.

References

Pastures Australia (n.d.) Siratro Fact Sheet. Retrieved September 2018 from https://keys.lucidcentral.org/keys/v3/pastures/Html/Siratro.htm

PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved September 2018 from: http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Macroptilium~atropurpureum

Queensland Government. (2020). Invasive plant: Siratro Macroptilium atropurpureum Retrieved 2020 from:https://www.daf.qld.gov.au/__data/assets/pdf_file/0003/65289/siratro.pdf

More information

Control

Siratro is very palatable to livestock, therefore it is not usually a weed of pastures. Continuous heavy grazing will limit the growth.

Try to control plants before they produce seed.

Check controlled areas regularly and re-treat when needed.

Physical removal

Individual plants and small infestations can be hand pulled or dug out. This can be done year-round but will be easiest when the soil is damp. Take care when removing large plants as they have a bigger, hardier root system that can snap off and be left in the soil. It is important to remove all the roots, otherwise the plant can regrow.

Disposal

Contact your local council for advice on how to dispose of this weed.

Slashing

When plants are growing thickly amongst other vegetation they can be cut back using a brush cutter. This will not kill plants and follow up work will be needed to dig out the roots.

Cultivation

Cultivation can be used to control plants but it will also trigger the germination of seeds in the soil. Follow up control work will be necessary to manage seedlings.

Chemical control

Spraying

Spray actively growing plants. Ensure all of the foliage is covered in the herbicide mixture.

Stem scraping

This method is suitable when plants are climbing over native vegetation or other desirable plants. Lightly scrape the stems and apply the herbicide to the stem within 15 seconds. Do not scrape all the way around the stems.

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.

PERMIT 11916 Expires 31/03/2025
Glyphosate 360 g/L (Various products)
Rate: 1 part product to 100 parts water plus surfactant
Comments: Spot spray: Urban bushland, forests and coastal reserves.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

PERMIT 11916 Expires 31/03/2025
Glyphosate 360 g/L (Various products)
Rate: 1 part product to 1.5 parts water
Comments: Scrape stems: Urban bushland, forests and coastal reserves.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

Glufosinate-ammonium 200 g/L (Basta® )
Rate: 1 to 3L per Ha
Comments: Boom or directed sprayer. Commercial and industrial areas, rights of way and non-agricultural areas.
Withholding period: Variable, up to 16 weeks, see label for more information.
Herbicide group: 10 (previously group N), Inhibition of glutamine synthetase
Resistance risk: Moderate

Glufosinate-ammonium 200 g/L (Basta® )
Rate: 300 mL to 100 L of water
Comments: Hand gun application. Commercial and industrial areas, rights of way and non-agricultural areas.
Withholding period: Variable, up to 16 weeks, see label for more information.
Herbicide group: 10 (previously group N), Inhibition of glutamine synthetase
Resistance risk: Moderate

Glufosinate-ammonium 200 g/L (Basta® )
Rate: 45 mL to 15 L of water
Comments: Knapsack application. Commercial and industrial areas, rights of way and non-agricultural areas.
Withholding period: Variable, up to 16 weeks, see label for more information.
Herbicide group: 10 (previously group N), Inhibition of glutamine synthetase
Resistance risk: Moderate

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.

For technical advice and assistance with identification please contact your local council weeds officer.

Reviewed 2020