The whole plant grows from a long white, sometimes branched, taproot which has numerous lateral roots. 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. 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. Spread of seed in gravel, topsoil and compost is also important and is of growing concern in the Auckland Region. Plant material should be buried deeply or burnt, so children or animals do not have access to it. Chemical Control Larger infestations of hemlock can be treated with a herbicide before it flowers.