There are many dangerous plants which grow in and around Kent.

Last month, work on improving a stretch of the M20 was briefly delayed after deadly foliage was found growing at the side of the road.

The discovery of hemlock surprised many, with its use as a poison dating back centuries.

To avoid any problems for the workers between junctions 3 and 5, from Sevenoaks to Aylesford, a cordon was thrown up around it.

But it’s growth in the county is not as uncommon as the motorway drama may suggest. It can often be found in verges and on riverbanks.

So as many of us head into the countryside during the school holidays to take advantage of the natural environment, should we be concerned about plants growing within it?

The short answer is no.

Richard Barnes, senior conservation advisor to conservation charity the Woodland Trust, said: “A plant which has the potential to pose a danger is usually due to a desire to deter some of their own particular pests.

“Some can be selective, so berries which are not poisonous to birds for example, because they want them to eat them and not others.

“There are plenty of other good things to do in the woods just don’t eat anything you find.”

But how do you identify what can be harmful if ingested? The trick is to take no chances.

“During the 1970s and 80s we had the Countryside Code drilled into us,” explained Mr Barnes, “and that included not picking something you weren’t certain about, leaving gates as you found them and cleaning up litter.

“If you’re encouraging someone to go foraging then you need to be alert, but otherwise, as long as you’re not eating plants and berries, you’ll be perfectly fine.”

The Woodland Trust’s foraging guidelines spell out the basics.

It says: “Never consume a wild plant or fungus unless you are absolutely certain of its identification. It could be rare and protected, inedible or even deadly poisonous.

“If you’re unsure it’s best to leave alone.”

So while they can all look very pretty, just what plants pack a punch? The Woodland Trust’s guidance is as follows:

Hemlock

(Conium maculatum)

Often referred to simply as ‘poison hemlock’ the name tells the story.

Sometimes confused with other species in the Apiaceae family such as cow parsley, it’s a large plant which can grown two metres tall, with hollow, purple-blotched stems.

It can often be found in damp areas along the edges of woodland, along ditches, streams and roadside verges.

Hemlock contains several toxic alkaloids including coniine and is poisonous to humans and livestock. Consumption of just a small amount of any part of the plant can cause respiratory paralysis and death.

Foxglove

(Digitalis purpurea)

A familiar sight across Kent, it grows with tall pink and purple flowers in the early summer - and is often a popular plant in gardens.

But should you try and nibble on it, you may find yourself in all sorts of trouble.

It grows throughout the UK, along woodland edges, roadside verges and hedgerows.

Foxgloves contain toxic cardiac glycosides. Ingestion of any parts of the plant can result in severe poisoning.

Symptoms include nausea, headache, skin irritation and diarrhoea. In severe cases it can lead to visual and perceptual disturbances and heart and kidney problems.

The cardiac glycosides from foxglove have been used medicinally to make a heart stimulant drug. Foxgloves have also widely been used in folk medicine.

Lords-and-ladies

(Arum maculatum)

Also known as cuckoo pint, you’ll find this plant in woodland and along hedgerows.

It has large, arrow-shaped, purple-spotted leaves at the base of the plant. Its berries are green, orange or red, depending on their ripeness.

Take care when handling this plant. All parts of it can cause allergic reactions, but the berries are particularly poisonous.

The plant contains minute needle-shaped crystals which can severely irritate the skin. Consumption of the plant can lead to throat swelling, breathing difficulties and stomach irritation.

However, it’s difficult to accidentally consume large quantities of this plant because it has an acrid taste and gives a tingling sensation which acts as a warning.

Deadly nightshade

(Atropa belladonna)

Another where the name surely tells you something, and its reputation proceeds it.

It has purple-green, bell-shaped flowers and untoothed, oval leaves. The berries are green and they ripen to black. Found mainly in the southern half of the UK, it lurks in woodland, along paths and in scrubby areas.

All parts of the plant are toxic, but the berries are especially poisonous. They contain a mixture of tropane alkaloids that affect the nervous system.

Atropine, in particular, causes severe symptoms in humans, including sweating, vomiting, breathing difficulties, confusion, hallucinations and potential coma and death.

It also has a pupil-widening effect that was known in ancient Greece. An extract of ‘belladonna’ (Italian for ‘beautiful woman’) was applied by women to enlarge their pupils.

Monkshood

(Aconitum napellus)

Also known as Adam and Eve or devil’s helmet, this is one of the UK’s most poisonous plants.

It’s widely naturalised, but may be native in damp woodlands, meadows and along ditches in the southern half of the UK.

Its attractive hooded, blue flowers have made it a popular garden plant and you’ll find cultivars in varying colours including pink, yellow and white. Its flowers grow on tall spikes that bloom between June and September.

All parts of the plant are poisonous, particularly the roots. If ingested, it can cause stomach and dizziness.

The poison also affects the heart and in large amounts can be fatal, but poisonings are rare as it has such an unpleasant flavour.

Toxins can even transfer to the skin via cuts, so it is important to always wear gloves when handling plants in your garden.

Several species of Aconitum have been used as arrow poisons.

They have been used in the Aleutian Islands in Alaska to poison harpoon tips used in whaling.

The world's first chemical weapon

The rhododendron is a pretty common site in gardens and parks around the county - but did you know it is also responsible for producing what experts at Kew Gardens describe as “the world’s first recorded chemical weapons”?

A non-native species, it was introduced to the UK in the late 18th century - believed to have been popular with large estates to use as cover for game birds and botanical gardens and most likely originating from Spain or Portugal.

But while a household name, they can be a threat. In particular the honey produced by the plant - as, the history books retell, to devastating effect.

Philip Stevenson, professor of plant chemistry at the Royal Botanic Gardens, Kew and Natural Resources Institute, said: “Several historical accounts from what is now modern Turkey cite the use of so-called ‘mad’ honey to stupefy naïve invading armies making them easier to attack.

“Mad honey was the toxic honey produced by bees feeding on nectar of rhododendron ponticum in its native northern Turkey.

“Perhaps the most notable example was King Mithridates VI of Pontus: he was an early experimentalist with natural poisons, and placed the toxic honeycombs from the hives of honeybees that had been foraging on rhododendron strategically along the roadside in advance of the invading army of Pompey the Great in 65BCE, as a trap.

“The Roman garrison marching along the road sometime later stumbled upon this apparent gift from the gods and not recognising the danger, enthusiastically scoffed it, unwittingly poisoning themselves in the process.

“While in their toxin induced stupor they were helplessly slaughtered by the army of Mithridates VI which was lying in wait.”

What to do in the case of accidental poisoning

• If you think a child or adult has eaten part of a suspect plant, seek medical advice immediately from a hospital accident & emergency department.

• Take a sample of the plant with you (as many parts of the plant as you can for accurate identification - eg leaves, flowers, fruits, stem).

• Do not panic and do not try to make the person sick.

• In the case of animals, seek veterinary advice if you think an animal has eaten a poisonous plant. Take along samples of the plant.