Japanese sunflower (Tithonia diversifolia)

Also known as: Mexican sunflower

Japanese sunflower is a perennial shrub with large yellow flowers. It forms dense thickets that compete with other plants.

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How does this weed affect you?

Japanese sunflower is an environmental weed in coastal regions of NSW. It

• forms dense thickets
• outcompetes native vegetation
• secretes chemicals that prevent other plants from growing.

In other countries it is also an agricultural weed. It can contaminate seed and reduce yields in crops such as sorghum and maize.

Where is it found?

Japanese sunflower is common on the North Coast of NSW. It also grows in the Hunter and Greater Sydney regions.

It is native to Central America. It is an ornamental plant and has been planted in gardens.

What type of environment does it grow in?

Japanese sunflower grows in tropical, sub-tropical and warm temperate climates, preferring 1000 mm to 2000 mm of rain per year. It can tolerate a wide range of soil types including soils with low fertility. It mostly grows in coastal areas, especially disturbed areas such as along roadsides and railways, embankments, forest edges and creek lines.

How does it spread?

By seed

Each plant can produce over 120 000 seeds. Seeds are most viable after 4 months of dormancy. The seeds are spread by:

• wind
• moving water
• attaching to animal fur or clothing
• moving contaminated fodder
• people dumping garden waste.

By plant parts

Japanese sunflower can grow from stem fragments. These can be spread by people dumping garden waste.

What does it look like?

Japanese sunflower is a robust, perennial, branching shrub that usually grows 1 to 3 m tall but can grow up to 5 m.

Leaves are:

• greyish green
• 7–33 cm long and 7–22 cm wide
• widely oval shaped or with 3 or 5 pointed lobes
• toothed along the edges
• pointed at the tips
• finely hairy
• alternate along the stem.

Flowers are:

• sunflowers with a yellow centre and have up to 15 yellow petals
• 10 - 19 cm wide
• in groups at the end of branches
• present from April-June.

Seeds are:

• black or mottled
• 5–6 mm long
• 4-angled with a ring of scales and 2 bristles (awns) 5 mm long.

Stems are:

• striped or ridged
• hairy when young.

Similar looking plants

Japanese sunflower looks like other weeds when they are not flowering:

• Mexican sunflower (Tithonia rotundifolia), which has orange or reddish petals and present in the Central West region of NSW.
• Wild sunflower (Helianthus annuus), which does not have lobed leaves and has orange to brown centres on the flowers.
• Anzac tree daisy (Montanoa hibiscifolia), which has smaller flowers with white petals.
• Paper mulberry (Broussonetia papyrifera), which looks similar when young but matures into a large deciduous tree. It has green and white flowers and prominent red fruit.

References

Atlas of Living Australia. (2020). Tithonia diversifolia. Retrieved 8 May 2020 from: https://bie.ala.org.au/species/https://id.biodiversity.org.au/node/apni/2900593

CABI. (2020).Tithonia diversifolia (Tithonia). In: Invasive Species Compendium. Wallingford, UK: CAB International. https://www.cabi.org/isc/datasheet/54020#tomeansOfMovementAndDispersal Retrieved 08/05/2020.

Identic Pty Ltd. and Lucid central  (2016). Environmental Weeds of Australia Fact sheet:  Tithonia diversifolia. Retrieved 22 June 2021 from: https://keyserver.lucidcentral.org/weeds/data/media/Html/tithonia_diversifolia.htm

Miranda, M. A., Varela, R. M., Torres, A., Molinillo, J. M., Gualtieri, S. C., & Macías, F. A. (2015). Phytotoxins from Tithonia diversifolia. Journal of Natural Products, 78(5), 1083-1092.

Muoghalu, J. I., & Chuba, D. K. (2005). Seed germination and reproductive strategies of Tithonia diversifolia (Hemsl.) Gray and Tithonia rotundifolia (PM) Blake. Applied ecology and environmental research, 3(1), 39-46.

PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved 22 June 2021 from:  http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Tithonia~diversifolia

More information

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Control

Successful weed control relies on follow up after the initial efforts. This means looking for and killing regrowth or new seedlings. Using a combination of control methods is usually more successful.

Physical removal

By hand

Dig out plants growing in small or isolated patches.

Slashing

Slash before flowering to prevent seeds from being produced. Follow up control works by digging out plants, continuously slashing, or spot spraying to prevent the plants from reaching maturity.  

Chemical control

Spot spraying

Spray plants before they flower. Apply herbicide to all foliage and stems to the point of visible wetness.

Cut stump method

Cut the stems and apply herbicide to the stump within 15 seconds of cutting.

Herbicide options

See Using herbicides for more information.

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Metsulfuron-methyl 300 g/kg + Aminopyralid 375 g/kg (Stinger™)
Rate: 20 g in 100 L of water
Comments: Hand gun application.
Withholding period: 3 - 56 days (see label)
Herbicide group: B, Inhibitors of acetolactate synthase (ALS inhibitors) + I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: High/Moderate

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Metsulfuron-methyl 600 g/kg (Various products)
Rate: 10 g in 100 L of water
Comments: Apply to actively growing plants after full leaf expansion but before seed set. Add surfactant.
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: B, Inhibitors of acetolactate synthase (ALS inhibitors)
Resistance risk: High

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Picloram 100 g/L + Triclopyr 300 g/L + Aminopyralid 8 g/L (Grazon Extra®)
Rate: 350 mL in 100 L of water
Comments: Apply as foliar spray pre-flowering
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

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Picloram 44.7 g/L + 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

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Triclopyr 300 g/L + Picloram 100 g/L (Various products)
Rate: 350 mL in 100 L of water
Comments: Apply as a foliar spray pre-flowering.
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 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.

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Reviewed 2021