Blue passionflower (Passiflora caerulea)

Blue passionflower is a climbing vine with distinctive blue and white flowers. It spreads quickly and smothers other vegetation.

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How does this weed affect you?

Blue passionflower is a weed of natural areas. It grows quickly and smothers native plants. The leaves and unripe fruit are poisonous. 

Poisoning

Blue passionflower leaves and unripe fruit contain cyanogenic glycosides which turn into cyanide when eaten. It can cause nausea and vomiting in humans and animals. Toxic parts of the plant are bitter and not usually eaten so poisoning is not common and rarely serious. The flesh in the ripe fruit is edible but bland and may still contain traces of toxins.

What to do if a person is poisoned:

  • 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.

What does it look like?

Blue passionflower is a hardy perennial vine. It is an excellent climber and can grow to more than 6 m. The plant has lots of tendrils which twist and coil their way around plants, fences and other structures for support.

Leaves are:

  • green, sometimes dull green-blue
  • 8-12 cm long with smooth edges
  • deeply divided usually with 5 lobes (sometimes no lobes on young plants)
  • deciduous 
  • stalks are 10-40 mm long with 2-4 small glands.

Flowers are:

  • 6-8 cm wide with a ring of blue, white and purple threads, sitting above greenish-white petals
  • perfumed
  • present from summer to early autumn
  • usually open at night.

Fruit are:

  • egg-shaped or roundish
  • 3-6 cm wide
  • green at first, ripening to orange-yellow.

Seeds are:

  • silver-brown
  • covered in slimy pulp
  • about 4-5 mm long.

Stems are:

  • hairless 
  • often angular
  • woody
  • fast growing.

Roots

It has an extensive fibrous root system.

Similar looking plants

Blue passionflower looks like edible passionfruit (Passiflora edulis) but edible passionfruit leaves have toothed edges.

Native passionfruit plants look similar, but have red, yellow, orange, pink or white flowers.

Where is it found?

It is a weed in the Illawarra region of NSW. A few scattered infestations have been found in the North coast, Northern tablelands, Hunter and Greater Sydney regions.

It also grows in Queensland, Australian Capital Territory, Victoria, Tasmania and South Australia. It is also a weed in New Zealand, Hawaii and USA. 

Blue passionflower comes from South America.

How does it spread?

Blue passionflower is used as rootstock for edible passionfruit plants.  It can easily sprout from below the graft. It can also sprout from the rootstock after the grafted plant dies. The plant then fruits producing viable seed.

By seed

Birds and other animals (pigs, possums, foxes) eat the ripe fruit and spread the seeds. Seeds can be slow to germinate. Wet conditions may promote sprouting.

By plant parts

Plants can also spread when stems touch the ground and send out new roots. If the rooted stem is separated from the main plant it can still survive. New plants can grow metres away from the parent plant.

References

Richardson FJ, Richardson RG and Shepherd RCH (2006). Weeds of the south-east an identification guide for Australia. RG and FJ Richardson, Melbourne.

Department of Employment, Economic Development and Innovation (2011) Blue passionflower, Passiflora caerulea. Queensland Government. Available at: http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/Passiflora_caerulea.htm. Accessed 2014.

More information

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Control

Blue passionflower can be controlled by hand pulling, digging out or herbicides. 

Prevention

Check edible passionfruit vines regularly and trim any sprouts from below the graft. If edible passionfruit dies the root stock should be removed. Dispose of plants appropriately. Contact your local council for disposal methods.

Early detection

Learn to identify blue passionflower and remove plants early to reduce the chance of spread. Small plants are easier to dig up.

Slashing and mulching

Stems can be mown, or whipper-snipped regularly, but this will suppress growth, not kill the plant. Cutting stems down over many years may eventually kill the plants.

Physical removal

Small plants can be hand pulled or dug out. Make sure all roots are removed. This can be done year-round but will be easiest when the soil is damp. Do not leave stems in contact with soil as they can sprout roots and regrow.

Chemical control

The following herbicide techniques can be used to control blue passionflower: 

  • spot spraying
  • basal barking
  • cut, scrape and paint
  • splatter gun
  • leaf wiping.

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 9907 Expires 31/03/2025
Fluroxypyr 200 g/L (Starane™)
Rate: 500 mL to 1 L per 100 L water
Comments: Spot spray
Withholding period: 7 days.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


PERMIT 9907 Expires 31/03/2025
Fluroxypyr 200 g/L (Starane™)
Rate: 35 mL per L diesel/kerosene
Comments: Basal bark
Withholding period: 7 days.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


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: 7 days.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


PERMIT 9907 Expires 31/03/2025
Fluroxypyr 333 g/L (Starane™ Advanced)
Rate: 21 mL per L diesel/kerosene
Comments: Basal bark
Withholding period: 7 days.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate


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


PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L (Roundup®)
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


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


PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L (Roundup®)
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


PERMIT 9907 Expires 31/03/2025
Metsulfuron-methyl 600 g/kg (Brush-off®)
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


PERMIT 9907 Expires 31/03/2025
Metsulfuron-methyl 600 g/kg (Brush-off®)
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 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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For technical advice and assistance with identification please contact your local council weeds officer.
For further information call the NSW DPI Biosecurity Helpline on 1800 680 244 or send an email to weeds@dpi.nsw.gov.au

Reviewed 2020