Common Heliotrope

Heliotropium europaeum L.

Family: Boraginaceae.

Names:

Heliotropium is from the Greek words 'helios' or sun and 'tropaios' meaning to turn back and refers to the flowers following the sun.
Europaeum refers to its area of origin in Europe.
Common Heliotrope because it is the most common species of Heliotropium in Europe.

Other names:

Caterpillar Weed because flower head looks like furry caterpillars.
Barooga Weed
European Heliotrope because it comes from Europe.
Potato Weed because its leaves and growth habit resemble the potato.
Wild Heliotrope
Wanderie or Wandary Curse.

Summary:

A grey green, hairy, summer growing, annual herb with obvious veins in the loose rosette of leaves. The white flowers are carried in coiled spikes on softly hairy stems. It usually has an offensive smell when crushed.

Description:

Cotyledons:

Two. Round. Tip round. Sides convex. Base tapered to squarish. Surface with fine hairs on all parts. Petiole longer than the blade and hairy.

First leaves:

Oval, 15-50 mm, prominent veins. Petiole up to as long as the leaf blade. Tip tapering to a point. Opposite in pairs. Finely hairy, especially on the under surface.

Leaves:

Alternate. They usually have an unpleasant odour when crushed.
Stipules - Present.
Petiole - 5-30 mm long. Slender.
Blade - Grey green on top and lighter colour on the underside, egg shaped to oval or oblong, 10-90 mm long x 7.5-30 mm wide, tough. Rounded tip. Upper surface rough to touch. Densely hairy with hairs arising from warts. Obvious veins indented into the upper leaf surface. Abruptly narrowed to the petiole. Edges are not wavy. Abruptly narrowed at the base into the petiole.

Stems:

Grey green, erect or bending upwards, usually branched, rough to touch. 100-500 mm long. Short woolly or coarse white hairs.

Flower head:

Crowded cluster (cyme) at the ends of stems or in leaf axils. Simple or a few branches. Flowers in 2 rows on the upper side of a coiled spike that is 50-110 mm long when straightened. Spikes single or in pairs, initially coiled and straightening as seeds ripen. Looks like a caterpillar.

Flowers:

White with a yellow throat, tubular. Scentless.
Bracts - None.
Ovary - style is in glandular ring about 0.5 mm diameter with a 1 mm conical stigma with sparse short hairs.
Sepals - 5 lobes almost free to the base, narrowly egg shaped, 2-3 mm long. Densely hairy. Persistent and somewhat spreading after the fruit has fallen.
Petals - 5, tubular, green and hairy at the base, white and less hairy near the top, 2-3 mm long x 3-6 wide when open, with 5 round tipped, spreading lobes up to 1 mm long. Hairless inside. The petal tube is often swollen below the middle.
Stamens - No filament.
Anthers - No stalk (filament). 1 mm long. Attached near the middle of the corolla (petal) tube.

Fruit:

4 warty or wrinkled, 1 seeded nutlets. Occasionally hairy on one side.

Seeds:

Black to brown. Almost globular to tear shaped, about 1 mm diameter. Surface warty.

Roots:

Well developed slender taproot over 1 m deep with many branches. Root fragments don't shoot when broken by cultivation.

Key Characters:

Hairy. Distinct petiole. Corolla throat hairless inside. Sepals divided almost to the base and persistent. Leaves rough to touch with short hairs and egg shaped to elliptical. Annual.
Coiled caterpillar like flower head with white, 5-petalled, tubular flowers with a yellow throat.
Leaves usually have an unpleasant smell when crushed.
Woolly whitish stems.

Biology:

Life cycle:

Annual. Seeds germinate in late spring and summer, especially after summer rain. Top growth, for early germinating plants, is slow initially as the root systems develop. It can withstand drought soon after emergence. Top growth grows through summer and dies back in late autumn with the first frosts. Late germinating plants may flower within a month of emergence, at the 5-7 leaf stage, and have ripe seed 2-3 weeks later. Several generations can occur within the one season. Leafy secondary shoots emerge from the lower leaf axils and flower in turn. This process continues all summer if moisture is available.
Despite its germination late in the year, it can grow and set seed quickly enough to be harvested with grain crops in summer.

Physiology:

Frost sensitive.
Sensitive to competition.

Reproduction:

By seed.

Flowering times:

Mainly summer and late autumn in western NSW.
Most of the year in SA.
Summer and autumn in WA or may be most of the year in areas where temperatures are greater than 150C.

Seed Biology and Germination:

Seeds won't germinate below 150C and have an optimum at 30-350C.
Stratification improves germination.
Hard seeded and persistent.

Vegetative Propagules:

None.

Hybrids:

Allelopathy:

Population Dynamics and Dispersal:

Long distance spread is usually in contaminated grain, produce and attached to transported stock. Local spread is mainly by stock. The fruits attach to wool, fur and clothing. Seed will survive the passage through animals. Flood waters and mud on stock or vehicles also account for some spread.
Density varies from scattered plants in undisturbed areas through to very dense infestations in disturbed areas and fallows.

Origin and History:

Southern and central Europe, Western Asia and North Africa.
Introduced to SA in the 1800's and first recorded in 1880.

Distribution:

ACT, NSW, QLD, SA, VIC, WA.
South west and eastern goldfields in WA.

Courtesy Australia's Virtual Herbarium.

Habitats:

Climate:

Temperate regions.
Most prevalent in areas with 300-500 mm of predominantly winter rainfall.

Soil:

It occurs on a wide range of soil types, but seems to prefer the loams to heavier soil types and alkaline soils.

Plant Associations:

Prefers open areas dominated by winter annuals.
Often more common on firebreaks.

Significance:

Beneficial:

Fodder.
Does not host Root Lesion Nematode (Pratylenchus neglectus) (64).

Detrimental:

Weed of cereal crops, pastures, fallows, firebreaks, roadsides and disturbed areas.
Contaminates cereal grain and only low levels are tolerated without price penalties. In some markets there is zero tolerance.
Contains alkaloids.
Toxic to livestock and humans.
It is a poor host for Root Lesion Nematode (Pratylenchus thornei) allowing some build up of numbers (64).

Toxicity:

Contains pyrrolizidine alkaloids which are liver toxins and carcinogenic, and they are considered more toxic than those found in Blue Heliotrope (H amplexicaule).
Causes copper poisoning in sheep, cattle and horses. Causes liver damage and/or photo-sensitisation after prolonged or repeated grazing of dense infestations. The palatability appears variable. Merinos generally find it unpalatable and graze amongst it, whereas crossbreds and British breeds are more regularly poisoned. Both green and dry plants may be grazed. Cattle are more susceptible than sheep and horses are the most susceptible. Deaths may take many months to occur, or it may reduce life span, or it may make stock more susceptible to poisoning by other plants such as Paterson's Curse. Up to 30% mortalities have been recorded where sheep graze Paterson's Curse in the winter and Common Heliotrope in the summer.
Seeds in feed wheat may affect pigs and poultry.
It is readily eaten by cattle causing frequent deaths especially in young animals. Horses are more sensitive than other stock and lose weight and die if confined to infested areas.
It may cause toxaemic jaundice in sheep.
Both the seeds and leaves contain at least 5 toxic alkaloids which are liver toxins and carcinogenic. The toxicity is cumulative.
These toxins also affect humans and it is expected that they will be present in honey taken from infested areas. It is not known what effect on health this may have.

Symptoms:

Direct poisoning symptoms usually occur within a few weeks of exposure. Cattle deaths may occur with few symptoms or jaundice, red urine and photo-sensitisation.
With indirect poisoning, due to copper toxicity, symptoms usually only appear in the second season after exposure. Sudden death may occur soon after stresses like cold conditions or droving and may occur some time after removal from infested areas.

Treatment:

Provide alternative feed.
Remove stock from infested areas if they are grazing the plant.
Don't feed contaminated grain to pigs or poultry.
Cobalt supplements may provide marginal protection.

Legislation:

Noxious weed of WA and Tas.

Management and Control:

Seeds mainly spread in produce or by stock. The hairy nutlets attach to animal wool and hair. Seed passing through animal guts is unaffected. The extended flowering period means there is usually ripe seed when agricultural seeds are harvested. Seed also moves in water flows. It is sensitive to competition and is rarely found in healthy perennial pastures. Cropping favours its establishment. Cultivation will control seedlings present but needs to be repeated for each new germination. Maintaining good ground cover over spring and summer helps to reduce infestations. Hormone herbicides, amitrole, bromoxynil, glufosinate, glyphosate, metsulfuron and triasulfuron control seedlings. The hormone herbicides lose effectiveness when the plants start their reproductive growth. Chlorsulfuron and triasulfuron are effective on young plants and have some residual activity which helps control subsequent germinations. However, the occurrence of the weed on alkaline soils often restricts the use chlorsulfuron and triasulfuron due to long plant back periods for broadleaf crops and pastures. Diquat, paraquat, glyphosate, amitrole and terbutryn are more effective on old plants.

Thresholds:

Eradication strategies:

Establish or encourage perennials based pastures such as phalaris plus clover.

Herbicide resistance:

Biological Control:

Several insects have been released for biocontrol without much success.
A rust fungus was released in 1991.
The Heliotrope moth (Utetheisa pulchelloides) is a white spotted moth and often seen in Heliotrope and Paterson's Curse infestations. The caterpillars have sparse grey hairs, and are black with orange spots and broken cream lines along the body.

Related plants:

Blue Heliotrope (H. amplexicaule)
Rough Heliotrope (H. asperrimum)
Smooth Heliotrope (H. curassavicum)
(H. indicum)
(H. supinum)

Plants of similar appearance:

References:

Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P127. Photo.

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P711. Diagram.

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P306.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). p563. Photo.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P119-122. Photo.

Gardner, G.A. and Bennetts, H.W. (1956). The toxic plants of Western Australia. (West Australian Newspapers Ltd, Perth). p157.

Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P112. Photo.

Hyde-Wyatt, B.H. and Morris, D.I. (1980) The Noxious and Secondary Weeds of Tasmania. (Tasmanian Department of Agriculture, Hobart, Tasmania). P107.

Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).

Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #635.4.

Marchant, N.G., Wheeler, J.R., Rye, B.L., Bennett, E.M., Lander, N.S. and Macfarlane, T.D. (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P549.

McBarron, E.J. (1983). Poisonous plants. (Inkata Press, Melbourne). P75. Diagram.

Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). P335-338. Photos.

Wilding, J.L. et al. (1987). Crop weeds. (Inkata Press, Melbourne). P70-71. Diagrams. Photos.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.