|Botanical Name||Conium maculatum|
|Origin||Europe, Asia, Nth Africa|
DescriptionHemlock is an erect annual or biennial herb growing up to two metres high that reproduces by seed. It has erect, hollow, hairless stems which are marked with purple blotches. The hairless, alternate leaves are up to 500mm long, fernlike with deep cut segments. The small white flowers are 2 to 4mm in diameter and are found in dense compound flowerheads at the ends of stems (flowers look similar to parsley, chervil, parsnip, celery and carrot). Small grey or brown, seed-bearing fruits are produced and these consist of two sections each 2 to 4mm long. The whole plant grows from a long white, sometimes branched, taproot which has numerous lateral roots. Please note: Wild carrot (Daucus carota) and fennel (Foeniculum vulgare) growing on roadsides and waste places is often mistaken for hemlock. However both of these have solid stems, while wild carrot has hairy stems and only grows to 1-2 metres. Wild carrot flowers are more tightly compact, are rounder in shape than hemlock and often have a pink tinge. Hemlock has an offensive odour when crushed whilst fennel smells like aniseed and wild carrot like carrot.
Where is it found?Waste land, especially damp locations.
Why is it a problem?Hemlock contains the very toxic alkaloid coniine in all of its parts, particularly the seeds and is very poisonous to both humans and stock. Animals are not generally attracted to the plant, however hemlock is sometimes consumed in hay, chaff or silage and is equally toxic when dry or cut. New Zealanders have been poisoned when mistaking the leaves of other edible garden plants such as parsley, carrots, wild carrots, fennel, parsnip, angelica, celery and chervil. Poisoning can also occur from skin absorption. Symptoms of poisoning are salivation, bloating, pain vomiting, loss of balance, irregular breathing, convulsions and sometimes loss of sight. Death is caused by respiratory paralysis.
How does it spread?Hemlock spreads solely by seeds which adhere to farm machinery, vehicles agricultural produce, mud and clothing, as well as being carried by water. Spread of seed in gravel, topsoil and compost is also important.
How do I get rid of it?
Individual plants should be pulled or hoed out before they flower. Plant material should be buried deeply or burnt, so children or animals do not have access to it.
Larger infestations of hemlock can be treated with a herbicide before it flowers. Any of the following chemicals can be used:
Metsulfuron - Gunspray: Mix 5 grams per 100 litres water Knapsack: Mix 1 gram per 10 litres water
Tordon Gold - Gunspray: Mix 500 ml per 100 litres water Knapsack: Mix 120 ml per 10 litres water
Glypholsate - Gunspray: Mix 1 litre per 100 litres water Knapsack: Mix 100 ml per 10 lites water
Tordon 2G granules: Apply 30 grams per square metre during winter
For more information on the poisonous properties of Hemlock please refer to Bay of Plenty Regional Council's Fact Sheet on Poisonous Plants.