Blue heliotrope

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Contacts and Further Information

If you find this weed please help to prevent its further spread by contacting your local Council Weeds Officer for positive identification and further assistance.

Alternatively call the NSW NSW Invasive Plants and Animals Enquiry Line on
1800 680 244 or send an email to weeds@dpi.nsw.gov.au









NSW No Space 4 Weeds

Blue heliotrope (Heliotropium amplexicaule)

Impact | Habitat | Description | Life cycle | Spread | Toxicity | Control & Management | Legislation

Blue heliotrope is a summer-growing perennial herb. It is extremely drought-hardy, which increases its ability to persist and spread and has made it a major agricultural weed in NSW.

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).

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.

Blue heliotrope is a noxious weed in many local control areas in NSW.

Impact

Blue heliotrope competes with desirable pasture plants and causes toxicity to stock. It is widespread because it is a highly persistent perennial, adaptable to a wide range of soil and climate types. It occupies more than 110 000 hectares in NSW.

Habitat

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.

Description

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

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.

Life cycle

The plant is adapted to a wide range of habitats, and can reproduce from both seed and root fragments that occur throughout the soil profile.

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

The fruit develops into two nutlets, each containing two seeds.

Spread

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.

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
Reduced productivity
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

Management and 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 criticial to the control of this weed.

Maintaining a vigorous summer-growing perennial pasture to out-compete 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 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, 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.

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.

Refer to the I&I NSW Noxious and environmental weed control handbook for the recommended chemicals to control blue heliotrope.

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.

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.

Legislation

Blue heliotrope is a Class 4 noxious weed under the NSW Noxious Weeds Act 1993 in many areas of NSW.

Class 4 control requirements are that ‘the growth of the plant must be managed in a manner that reduces its numbers spread and incidence and continuously inhibits its reproduction’.

The responsibility for control of noxious weeds on private land rests with the landowner or occupier of the land.

Acknowledgements

Information for this Primefact was taken from:

  • Da Silva, E 1991, ‘The ecology and control of blue heliotrope (Heliotropium amplexicaule Vahl)’, Final Report.
  • The work done by Royce Holtkamp, Jim Dellow, Graeme Kelso and Barney Milne, NSW Agriculture.

The authors would like to acknowledge the comments made by Rob Walker, Royce Holtkamp and Col Mullen regarding the technical content of this publication.


Last updated: July 2008.