Hemlock

Conium maculatum L.

Family: Apiaceae.

Names:

Conium is from Neo-Latin from the Greek word koneion meaning hemlock.
Maculatum is from the Latin macula meaning a spot and refers to the blotches on the stems.
Hemlock is of uncertain origin but may be derived from 'straw plant' referring to its hollow stems or 'hop plant' referring to its sedative effect similar to hops.

Other Names:

Carrot Fern
Poison Hemlock (North America)
Poison Parsley
Spotted Hemlock

Summary:

A many branched, robust, biennial or annual herb, usually 1.5 metres tall with twice divided leaves, many white flowers in spring in umbrella like arrangements at the top and with an unpleasant mousy or parsnip like smell when crushed. The stems are hollow and usually have distinctive purplish blotches.

Description:

Cotyledons:

Two. Oval cotyledons about 15 mm long with a distinct petiole and clearly marked longitudinal veins. There is a hypocotyl but no epicotyl.

First leaves:

Large compact cluster at ground level.

Leaves:

Strong mousy odour when crushed.
Stipules - None.
Petiole - Lower ones, hollow long with sheathing concave bases and often with purple spots. Upper one shorter with narrower bases.
Blade - Pale green, shiny. Triangular in overall outline, up to 500 mm long. Compound and pinnate with the leaflets pinnately sub-divided (carrot or fern like) with flat, narrow, serrated segments that are 10-30 mm long with cartilaginous tips. The youngest leaves are less divided than the older rosette and stem leaves.
Stem leaves - Alternate.

Stems:

Erect, robust, stiff, reaching 3000 mm in height, usually 1000-1500 mm tall, many branched, ridged and hollow(except at the nodes), with distinct black to purple or dark red blotches, especially on the lower parts. Hairless with a waxy bloom. Strong mousy odour when crushed.

Flower head:

Corymbose panicle. Large numbers of flowers on umbrella-like compound umbels of 10-20 main rays(stalks) that are 20-40 mm long with green, triangular, membranous edged, bracts underneath. Each ray carries about 20 flowers on short stalks. The terminal umbel has bisexual flowers and the side umbels have male and bisexual flowers. At the ends of stems or in upper axils.

Flowers:

About 2-5 mm in diameter.
Bracts - Ring of 5, small, backward bending, parallel sided bracts surrounds the base of the lower umbel and 3 small bracts on one side of the base of the secondary umbel.
Ovary -
Sepals - None.
Petals - Five, white, incurved petals that are egg shaped with a broad shallow notch at the top
Stamens - 5.
Anthers - 5.

Fruit:

Pair of grey brown fruitlets, broad egg shaped to globular, flattened. Each fruitlet 2.5-3.5 mm long x 2-3 mm wide and has 5, often wavy edged, round toothed, ribs. May or may not have aromatic oil tubes (vittas).

Seeds:

Furrowed on the inner face. Remains on the plant.

Roots:

White, occasionally branched, strong taproot with many laterals.

Key Characters:

Mousy smell. Purple stem markings. White umbrella like flower head.

Biology:

Life cycle:

Biennial or annual. Seedlings germinate in autumn and sometimes in spring, producing a coarse rosette initially and a deep taproot. Some plants flower in their first spring or summer and die. Others remain vegetative and flower in their second spring and summer then die. It may become perennial in regularly cut situations like lucerne.

Physiology:

Reproduction:

By seed.

Flowering times:

October to November in SA.
October to November in WA.

Seed Biology and Germination:

Seed is probably short lived in the soil.

Vegetative Propagules:

Hybrids:

Allelopathy:

Population Dynamics and Dispersal:

The plant reproduces from seed and the main method of dispersal is in water, or by being carried on animals or machinery or in gravel and land fill. Wind may cause some spread.

Origin and History:

Temperate Eurasia.
Probably in Tasmania in 1845, Victoria in 1871.

Distribution:

ACT, NSW, QLD, SA, TAS, VIC, WA.
Small patches can be found in all the higher rainfall areas of Tasmania, and occasionally in wet areas in the drier Midlands.

Courtesy Australia's Virtual Herbarium.

Habitats:

Climate:

Humid and subhumid temperate areas. Cooler regions.

Soil:

Damp fertile soils.
Prefers loams.

Plant Associations:

Shaded areas.

Significance:

Beneficial:

Ornamental.
Ancient Greeks used it to poison prisoners including Socrates.
Medicinal plant used as a sedative for treating epilepsy, gout, tumours and ulcers.
Used as a vegetable after careful cooking to destroy toxins.
Used as arrow poison by American Indians.

Detrimental:

Very toxic.
Weed of moist areas, especially along roadsides, ditches, creeks, lucerne, gardens, alluvial flats, rubbish dumps, disturbed areas and in pasture.
May cause dermatitis after handling in some people.
Hosts carrot fly and celery yellow spot.
Generally it is not a significant weed of agriculture in Australia.

Toxicity:

Very toxic plant. Contains a number of toxic alkaloids.
Eating leaves, roots and seeds mistakenly have caused human deaths. Leaves may be mistaken for parsley, roots for parsnip and seed for aniseed. Blowing through its hollow stems is also reported to have caused death.
Most toxic when green and varies with climatic conditions.
Livestock usually don't eat the plant but contaminated fodder can cause problems. Many cases of poisoning in cattle, pigs, horses and poultry are reported. Sheep and goats appear to be more tolerant. Young stock are more susceptible than old stock.
Taints milk.
Secondary poisoning may occur, a dog died after eating quail that survived feeding tests on seed.
Toxic, volatile alkaloids lost slow drying or boiling.

Symptoms:

May cause birth defects in calves and pigs.
Nervousness, trembling, difficulty in movement, especially hind limbs, stumbling, dilation of pupils, slow weak pulse initially then becoming rapid and thready, lowered body temperature, salivation, convulsions, stupor, paralysis then death from respiratory failure. Mousy odour on the breath and in the urine.

Treatment:

Tannic acid (4% solution) in water, 30-60 mL for sheep, 600 mL for cattle followed by a purgative or
Stimulants such as strong coffee, tea, alcohol or an infusion of wattle bark or boiled down water and flour or tincture of iodine diluted 1:200, repeated several times as necessary.
Animals that survive 8 hours usually recover.
Avoid grazing infested areas, especially young growth before flowering and seed.

Legislation:

Noxious weed of ACT, NT, SA, Tas and Vic.

Management and Control:

Thresholds:

Eradication strategies:

Regular spraying with 2,4-D when the plants are young has led to virtual eradication in Southern Queensland. Spraying with 2,4-D may increase the palatability and thus the risk of poisoning stock. Amitrole and other hormone herbicides such as MCPA and dicamba are also effective. Isolated patches could be sprayed with Tordon® to provide a kill of the plant and residual control of following germinations.
Manually remove isolated plants. Thicker stands can be cultivated.
Establish a vigorous pasture.
Mowing or slashing just before flowering is sometimes effective, but regrowth may occur.

Herbicide resistance:

Biological Control:

Related plants:

None.

Plants of similar appearance:

Bishop' Weed (Ammi majus) is similar but has less finely divided leaves, no purple stem markings and no mousy smell.
Fennel (Foeniculum vulgare) has solid stems filled with white spongy pith.
Wild Carrot or Quean Anne's Lace (Daucus carota) often has a single dark red flower in the centre of the umbel or cluster of flowers. It has bi-pinnate and tri-pinnate leaves, fine hairs on the stems and leaves, a root that smells like carrot when crushed.

References:

Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P74. Photo.

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P660. Diagram.

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P285-288. Diagram.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P717-720. Photo.

Gardner, G.A. and Bennetts, H.W. (1956). The toxic plants of Western Australia. (West Australian Newspapers Ltd, Perth). P146.

Hyde-Wyatt, B.H. and Morris, D.I. (1980) The Noxious and Secondary Weeds of Tasmania. (Tasmanian Department of Agriculture, Hobart, Tasmania). P69. Diagrams.

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). #341.1.

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). P505.

McBarron, E.J. (1983). Poisonous plants. (Inkata Press, Melbourne). P76. Diagram.

Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). P167-169. Photos.

Acknowledgments:

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