Laurel clock vine (Thunbergia grandiflora)

Also known as: blue sky vine

Laurel clock vine is a vigorous perennial climber. It is a major threat to remnant vegetation in the wet tropics.

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How does this weed affect you?

Thunbergia species were introduced to Australia as garden ornamentals but have escaped into native vegetation, and four species are now declared weeds in Queensland. They climb and smother native vegetation, shading out and killing the understorey and often pulling down mature trees with the weight of the vine.

What does it look like?

Laurel clock vine is a vigorous, perennial climbing vine.

It has oval-shaped leaves which narrow to a pointed tip. The leaves, mostly 70–180 mm long and 25–60 mm wide, grow in opposite pairs along the stem on stalks up to 60 mm long.

The trumpet-shaped flower begins as a short broad tube, white on the outside with a yellowish throat, and opens out into five rounded, pale lavender-blue petals, one larger than the others. The flowers are up to 80 mm long and 60–80 mm across, and are borne in clusters on long, drooping branches. 

The seed capsule is brown and inconspicuous. It is oval-shaped with pinched ends, 10 mm long and 4 mm wide. The capsules usually contain two to four hemispherical seeds which have a hollow inner surface like a cap. The seeds are less than 10 mm in diameter and covered with brown scales.

The plant develops a very tuberous root system, which can resprout from many dormant buds when cut.

Scientific name change

This plant was previously named Thunbergia laurifolia .

Where is it found?

Laurel clock vine is native to India and Malaysia. Until recently Thunbergia species, including laurel clock vine, were promoted and sold as garden plants. They are widespread in Queensland gardens, and are also common in eastern Australia as far south as Melbourne and occasionally extending to Adelaide, as well as across northern Western Australia and the Northern Territory (Darwin), and on Christmas Island. There are naturalised infestations in far north Queensland and Northern Territory. 

How does it spread?

Laurel clock weed mainly reproduces vegetatively, when cuttings or fragments of stems and roots take root and send out new shoots. It is often spread through the careless disposal of garden waste, or through contaminated earth being removed for fill or other soil use. Infestations along riverbanks have been caused by root pieces breaking off and being transported further downstream by floodwaters. 

What type of environment does it grow in?

Laurel clock vine grows in moist areas at low elevations and is most successful in frost-free locations. 

Acknowledgements

CRC for Australian Weed Management: Robyn Barker (SA Plant Biodiversity Centre), Peter van Haaren (Qld DNRM), Ken Murray (Cairns City Council), Sid Clayton (Mareeba Shire Council), Barbara Waterhouse (AQIS/Weeds CRC), Steve Csurhes (Qld DNRM), Philip Maher (Qld DNRM) and John Thorp (National Weeds Management Facilitator). 

More information

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Control

Control of laurel clock vine is very difficult because they can regenerate from extensive underground tubers if they are not all killed or removed. Chemical treatment is often the only option available. Check registered herbicides. Only small plants can be successfully controlled using physical removal because large mature plants normally have very large tuber systems that are virtually impossible to remove completely.

Cutting the vines at ground level will provide some temporary relief for a smothered tree but plants will regenerate from tubers, so follow-up control will be required. 

Take care when disposing of laurel clock vine because garden waste is a frequent source of new weed infestations. Contact your local council for specific advice before attempting to dispose of this plant. 

Herbicide options

See Using herbicides for more information.

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PERMIT 9907 Expires 31/03/2025
Fluroxypyr 200 g/L (Comet® 200 herbicide)
Rate: 500 mL to 1 L per 100 L water
Comments: Spot spray
Withholding period: Do not graze failed crops and treated pastures or cut for stock feed for 7 days after application. See label for further information.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate

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PERMIT 9907 Expires 31/03/2025
Fluroxypyr 200 g/L (Comet® 200 herbicide)
Rate: 35 mL per L diesel/kerosene
Comments: Basal bark
Withholding period: Do not graze failed crops and treated pastures or cut for stock feed for 7 days after application. See label for further information.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate

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PERMIT 9907 Expires 31/03/2025
Fluroxypyr 333 g/L (Starane™ Advanced)
Rate: 300 to 600 mL per 100 L water
Comments: Spot spray
Withholding period: Do not graze failed crops and treated pastures or cut for stock food for 7 days after application. See label for more information.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate

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PERMIT 9907 Expires 31/03/2025
Fluroxypyr 333 g/L (Starane™ Advanced)
Rate: 21 mL per L diesel/kerosene
Comments: Basal bark
Withholding period: Do not graze failed crops and treated pastures or cut for stock food for 7 days after application. See label for more information.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate

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PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L (Various products)
Rate: One part product to 50 parts water
Comments: Spot spray
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate

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PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L (Various products)
Rate: One part product to 1.5 parts water
Comments: Cut scrape and paint
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate

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PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L (Various products)
Rate: One part product to 9 parts water
Comments: Splatter gun
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate

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PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L (Various products)
Rate: One part product to 20 parts water
Comments: Wipe onto leaves
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate

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PERMIT 9907 Expires 31/03/2025
Metsulfuron-methyl 600 g/kg (Various products)
Rate: 10 - 20 g per 100 L water plus surfactant
Comments: Spot spray
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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PERMIT 9907 Expires 31/03/2025
Metsulfuron-methyl 600 g/kg (Various products)
Rate: 10 g per 1 L of water plus surfactant
Comments: Wipe onto leaves
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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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 2018