Blue heliotrope (Heliotropium amplexicaule)

Blue heliotrope is a summer-growing perennial herb. It is extremely drought-hardy, which makes it a major agricultural weed in NSW.

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How does this weed affect you?

Blue heliotrope is extremely drought-hardy, which increases its ability to persist and spread, and has made it a major agricultural weed in NSW. Blue heliotrope competes with desirable pasture plants and causes toxicity to stock. It is widespread and adaptable to a wide range of soil and climate types. It occupies more than 110 000 hectares in NSW.

Toxicity

Blue heliotrope contains pyrrolizidine alkaloids (PAs). These PAs are also found in common heliotrope (Heliotropium europaeum). The amount of PAs in blue heliotrope is much higher than in common heliotrope.

Heliotrope is not very palatable to livestock, and consequently tends to be avoided; however, some individuals continue to eat it indiscriminately. Heliotrope will be eaten if no other feed is available.

Continual ingestion by livestock of large amounts of heliotrope plants (either fresh or dried), or of their seeds as contaminants in stock feed, can cause liver damage and reduced productivity (see Table 1). In order of susceptibility, horses, pigs, cattle, sheep and goats can all be affected, with horses being the most susceptible.

All affected livestock species may become jaundiced and experience varying degrees of photosensitisation.

Table 1. Summary of livestock toxicity symptoms

Animal	Clinical Symptoms	Production Effects	Pathology
Horses	Weight loss, dull, depressed, uncoordinated, wander aimlessly. Can develop respiratory difficulties. Death	Reduced productivity	Liver damage and secondary brain damage
Pigs	Death		Liver, kidney and lung damage
Cattle	Depressed, unpredictable bouts of aggression. Death	Reduced productivity	Liver damage and secondary brain damage
Sheep, Goats	Can accumulate copper, which can cause sudden death when released.	Reduced productivity	Liver damage

What does it look like?

Blue heliotrope is a hairy, summer-growing, prostrate perennial herb, 15–30 cm high and 30–200 cm in diameter.

Blue heliotrope belongs to the Boraginaceae family which includes forget-me-nots (Myosotis spp), comfrey (Symphytum officinale), Paterson's curse (Echium plantagineium) and yellow burrweed (Amsinckia spp).

Stems

It has many hairy, branched stems radiating from a woody rootstock, and is highly aromatic.

Blue heliotrope has a strong, slender taproot that can be very woody. It generally extends to over 1 m, but has been observed at up to 2 m throughout the soil profile, with a complex system of lateral roots occurring at several depths.

Leaves

The leaves are alternate, dull green, soft and tapered at both ends.

Flowers

The flowers are bluish-purple with yellow centres. They grow in dense clusters along one side of a coiled stalk, often referred to as a fiddle neck.

Where is it found?

Blue heliotrope is a native of South America, and was probably introduced to Australia as an ornamental plant in the latter part of the 19th century. It was first reported in NSW in 1908 in the Hunter Valley, and since then has colonised large areas in NSW.

Maps and records

• Recorded presence of Blue heliotrope 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?

Blue heliotrope is adapted to a wide range of habitats, and can reproduce from both seed and root fragments. Blue heliotrope spreads aggressively, as it produces many sticky seeds that adhere to animals and machinery. Seed can pass unharmed through the digestive tracts of most animals. Blue heliotrope can also regenerate from root fragments. It is most commonly spread by road graders, farm machinery, livestock, humans and the movement of water along watercourses.

Flowering is largely dependent on rainfall, but usually starts in November and continues through summer until March. In frost-free areas, the plant is capable of growing and flowering at any time of the year after rain. Established plants produce a flush of new growth in spring and autumn, flowering profusely at these times. In warmer areas, plants may flower and set seed as early as July. The fruit develops into two nutlets, each containing two seeds.

The plant is frost-susceptible, dying off in winter and regenerating from the vigorous root system in the following spring.

What type of environment does it grow in?

Blue heliotrope is often found along roadsides, in waterways, on non-arable country, in degraded pastures and on fallowed cultivation.

Major infestations occur in areas receiving more than 500 mm of rainfall per year, although it is also established in low-rainfall areas, such as the western districts of NSW.

Acknowledgements

Prepared by Annette McCaffery, Alyssa Schembri and Annie Johnson, NSW Department of Primary Industries, July 2008.

The authors would like to acknowledge the work done by Royce Holtkamp, Jim Dellow, Graeme Kelso and Barney Milne, NSW Agriculture, and the comments made by Rob Walker, Royce Holtkamp and Col Mullen regarding the technical content of this publication.

References

Da Silva, E. 1991. The ecology and control of blue heliotrope (Heliotropium amplexicaule Vahl). Final Report to the Wool Research and Development Corporation, 33 pp. 

More information

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Control

Eradication of blue heliotrope is difficult. The effective control of this weed will usually involve a combination of the following options.

Pasture management

Overgrazing, which reduces competition from pasture, is a major cause of heliotrope infestation. Managing grazing pressure is critical to the control of this weed. Maintaining a vigorous summer-growing perennial pasture to out-compete blue heliotrope provides effective long-term control.

It is necessary to reduce the weed density using systemic herbicides before sowing a competitive perennial pasture. Advice on pasture management can be obtained from your local agronomist.

Grazing management

Where large infestations of blue heliotrope occur, sheep and goats can be used to manage heliotrope, provided a different group of animals is used each year.

The sheep rumen has a great capacity to degrade most of the poisons present in the plant. The merino has the greatest tolerance of heliotrope, but adult wethers should be used rather than breeding ewes or juveniles. British breed crossbred sheep are less selective grazers than merinos, and are more frequently affected by heliotrope poisoning.

Anecdotal evidence suggests that supplementing sheep with molybdenum and sulfate can reduce the chronic health effects of heliotrope poisons. The combined effect of molybdenum and sulfate is to reduce the accumulation of copper in the animal’s liver.

The aim of this practice is to either improve the short-term heliotrope tolerance of crossbred sheep or to allow the same group of merino sheep to be used to graze the plant over two or three successive seasons.

Correct grazing management to reduce PA toxicity is even more critical if Paterson’s curse is also present. In this situation, stock can be exposed to PAs during summer from the heliotrope and during the cooler months from the Paterson’s curse, increasing the risk of toxicity occurring from prolonged grazing.

Horses, pigs and cattle should never be used in the grazing management of blue or common heliotrope.

Cultivation

Cultivation gives short-term control of blue heliotrope, but also has the potential to spread the problem. To reduce the establishment of new plants from root fragments, it is best carried out after application of a systemic herbicide. Follow-up seedling control is essential.

Biological control

Biological control, if successful, has the potential to reduce the long-term economic and environmental costs of traditional herbicide control methods for blue heliotrope. There has only been one biological control agent released in Australia for blue heliotrope. The blue heliotrope leaf-beetle (Deuterocampta quadrijuga) was first released in Australia in 2001. At high densities, leaf-beetles can completely defoliate blue heliotrope, with both the larvae and adults feeding on the leaves. The blue heliotrope leaf-beetle has the potential to build up population levels rapidly, as each beetle lays several hundred eggs, however it is a difficult agent to establish requiring multiple, short interval releases.

Chemical control

Systemic herbicides play a critical role in the control of blue heliotrope, by helping to destroy their root system. Only a registered herbicide, used according to the directions on the label, should be used to control a weed. 

To improve the effectiveness of chemical control, herbicides should be applied to blue heliotrope when it is actively growing and commencing flowering (late February to March). Avoid spraying stressed plants.

Herbicide options

See Using herbicides for more information.

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PERMIT 89493 Expires 30/09/2026
Amitrole 250 g/L + Ammonium thiocyanate 220 g/L (Various products)
Rate: 1.1 L per 100 L of water
Comments: For spraying in riparian areas. Do not apply more than 2 applications per year. Do not broadcast spray over water. See permit for further restrictions and critical comments.
Withholding period: Nil
Herbicide group: 34 (previously group Q), Inhibition of lycopene cyclase
Resistance risk: Moderate

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PERMIT 94283 Expires 31/01/2029
Metsulfuron-methyl 600 g/kg (Various products)
Rate: 10 grams per 100 L of water plus 0.1 % surfactant.
Comments: Spray when plants are actively growing from late spring to autumn at commencement of flowering and before seed set. See permit for further critical comments.
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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2,4-D 300 g/L + Picloram 75 g/L (Tordon® 75-D)
Rate: 1.0 L per 100 L of water
Comments: Grass pastures only. Spot spray. Apply to young actively growing plants.
Withholding period: Do not graze or cut crops (except sugar cane 8 weeks) or pastures for stock food for 7 days after application.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Dicamba 750 g/L (Kamba® 750)
Rate: 87 mL per 15 L of water. Add a surfactant.
Comments: Spot spray prior to flowering. For non-crop situations.
Withholding period: Do not harvest, graze or cut for stock food for 7 days after application.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Dicamba 750 g/L (Kamba® 750)
Rate: 400 mL per 100 L of water. Add a surfactant.
Comments: Spray prior to flowering. For non crop situations.
Withholding period: Do not harvest, graze or cut for stock food for 7 days after application.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Dicamba 750 g/L (Kamba® 750)
Rate: 5.9 L/ha. Use a minimum of 1500 L/ha water carrier. Add a surfactant.
Comments: Boom spray for non-crop situations. Spray prior to flowering.
Withholding period: Do not harvest, graze or cut for stock food for 7 days after application.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Fluroxypyr 200 g/L (Various products)
Rate: 1.0 L per 100 L of water
Comments: Spot spray during flowering.
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: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Fluroxypyr 333 g/L (Starane™ Advanced)
Rate: 600 mL per 100 L of water
Comments: Spot spray during flowering.
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: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Picloram 100 g/L + Triclopyr 300 g/L + Aminopyralid 8 g/L (Grazon Extra®)
Rate: 500 mL per 100 L water
Comments: Boom spray: Apply a minimum spray volume of 1250 L/ha. Treat when 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: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Tebuthiuron 200 g/kg (Various products)
Rate: 0.5 g /m2
Comments: Pellet herbicide. Estimate the area within 30 cm beyond the drip zone of each target weed or group of weeds and calculate the amount of needed. Distribute the pellets uniformly within this area. Do not use within 30 m of trees. Do not apply to areas greater than 0.5 ha in size.
Withholding period: Nil.
Herbicide group: 5 (previously group C), Inhibition of photosynthesis at photosystem II - D1 Serine 264 binders (and other nonhistidine binders) (PS II Serine 264 inhibitors)
Resistance risk: Moderate

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Triclopyr 300 g/L + Picloram 100 g/L (Various products)
Rate: 500 mL per 100 L of water
Comments: Apply at flowering in a minimum spray volume of 1250 L/ha.
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.
Central Tablelands	Regional Recommended Measure* (for Regional Priority - Asset Protection) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should mitigate spread of the plant from their land. A person should not buy, sell, move, carry or release the plant into the environment. Land managers should reduce the impact of the plant on assets of high economic, environmental and/or social value.
Hunter	Regional Recommended Measure* (for Regional Priority - Asset Protection) Land managers should mitigate the risk of the plant being introduced to their land. Land managers should mitigate spread of the plant from their land. A person should not buy, sell, move, carry or release the plant into the environment. Land managers should reduce the impact of the plant on assets of high economic, environmental and/or social value.
North Coast Exclusion (eradication) zone: Bellingen Shire LGA, Coffs Harbour City LGA, Kempsey Shire LGA, Lord Howe Island, Nambucca Valley LGA, Port Macquarie-Hastings LGA. Core infestation (containment) zone: Ballina Shire LGA, Byron Shire LGA, Clarence Valley LGA, Kyogle Shire LGA, Lismore City 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.
	*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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Disclaimers

Pasture improvement may be associated with an increase in the incidence of certain livestock health disorders. Livestock and production losses from some disorders are possible. Management may need to be modified to minimise risk. Consult your veterinarian or adviser when planning pasture improvement. The Biodiversity Conservation Act 2016 and Local Land Services Amendment Act 2016 restrict some pasture improvement practices where existing pasture contains native species. Contact Local Land Services for further details.

Reviewed 2024