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Poison Hemlock Conium maculatum 

 
 
Attracts BeesBees are attracted to this plant
Attracts ButterfliesButterflies are attracted to this plant
Biennial Life CycleBiennial life cycle
Umbrella-Shaped FlowersUmbrella-shaped flowers
White FlowersWhite flowers
5 Petals5 petals
Jun-Jul Flowering
period
Pinnate LeavesPinnate leaves
Lobe-Edged LeavesLobe-edged leaves
Ribbed StemRibbed stem
Tap RootTap root
200cmMaximum height
 
 
  Main image of Poison Hemlock
© 2021 Adrian Briggs
 

Poison Hemlock is a non-native biennial plant of the UK, typically found growing in grassland, hedgerows and waste ground, to a mature height of up to 200cm.

Poison Hemlock is one of the most deadly plants to be found growing wild in the UK. It is also very common, found widely distributed across the UK. Even the ingestion of small amounts of any part of the plant, or skin absorption of the sap, can cause severe poisoning to humans and livestock. Poison Hemlock contains the toxic alkaloid Coniine and symptoms of poisoning include: gastrointestinal problems; irregular heartbeat; seizures and paralysis; respiratory failure; and death. Unfortunately there is no specific antidote to this toxin and so extreme care needs to be taken to avoid contact with the plant. Please see the notes below under 'Concerns' for details of plant identification.

Botanic classification and naming: Poison Hemlock is a member of the Carrot (Apiaceae) family. The genus name 'Conium' identifies the plant as a Poison Hemlock and its species name 'maculatum' means 'spotted (stems)'.

Concerns: All parts of Poison Hemlock are deadly toxic and unfortunately the plant leaves and white umbel flowers looks similar to several other members of the Carrot family, including Cow Parsley, Wild Carrot, Upright Hedge Parsley and Bur Chervil. Hemlock has been mistaken for Cow Parsley and Wild Carrot by foragers with fatal consequences. Accidental misidentification is all the more likely because both Poison Hemlock and Cow Parsley can be found growing close together. In view of this, foraging for members of the Carrot family is inadvisable and very strongly discouraged. However, it is important to be able to identify Poison Hemlock, to avoid any contact with the plant. Characteristics of Poison Hemlock to note include: a smooth and slightly-ribbed main stem; distinctive purple blotches on the stems (but these may be absent in young plants); rounded and hollow side branches; feathery leaves (finely divided between 2-4 times); and the plant is said to have an unpleasant mousy odour.

Benefits: Poison Hemlock is pollinated by bees and butterflies. It also provides a food source for moth caterpillars, such as those of the Poison Hemlock moth and Silver Ground Carpet moth.

Benefits to wildlife are also indicated with orange icons in the plant profile bar at the top.

 

 
Flower of Poison Hemlock

© 2021 Adrian Briggs

 

Flowers:
Poison Hemlock usually flowers between June and July.

Flower colour:

Flower Colour White

White

Flower shape:

Flower Shape  Umbrella

Umbrella

Petals:

Petal Number =  5

5

Leaf of Poison Hemlock

© 2021 Adrian Briggs

 

Leaves:

Leaf Shape:

Leaf Shape is Pinnate

Pinnate

Or:

Alternative Leaf Shape is Divided

Divided

Leaf Margins:

Leaf Margin is lobed

lobed

Stem of Poison Hemlock

© 2021 Adrian Briggs

 

Stem and Roots:

Stem shape:

Stem Shape is Ribbed

Ribbed

Root type:

Root Type is Tap

Tap