Have you considered plants may be classified as hazardous substances?

No good murder mystery would be complete without at least one fatality linked to an unknown poison, many of which prepared by the murder from extracts of seeds, leaves or roots of a conveniently nearby plant. Many of today’s drugs have their history and developed linked to materials which exist in nature.

Strychnine is made from the seeds of a poisonous nut, nicotine is extracted from tobacco plants , as a pure substance this is a very toxic poison. Curare has long been used in tropical South America as an extremely potent arrow poison. Death from curare is caused by asphyxia, because the skeletal muscles become relaxed and then paralyzed. If the poison is ingested it is relatively harmless..

Most employers are aware of the requirement to control exposure to hazardous substances in the forms of liquids, gases etc, fewer employers realise that the Control of Substances Hazardous to Health Regulations also cover biological agents such as bacteria, viruses and mould, especially those deemed to be pathogens which are harmful to human health. However there is another aspect to COSHH which may not have been considered which is particularly important for those involved in horticulture and the processing of plants or their products.

Although there are great benefits for the pleasant perfumes and appearance of many plants lurking beneath the surface  there may be a hidden risk. In history many have been used for both their healing and poisonous capabilities.

All substances are poisons – the difference is in the dose’

Although a majority of plants are harmless there are a few which can prove potentially hazardous. To put this into perspective there are tens of thousands of different plants but there are about a hundred or so which may cause concern if employees are in contact  with them or if your business could exposure others to certain plants, blubs and seeds (especially children who may find those bright berries very attractive to eat!)

Monkshood (aconitum napellus)

This is an extremely toxic plant, its leaves, seeds and roots are all poisonous. Dermatitis can result from regular handling, with the poison able to be absorbed through the skin without a cut. If swallow this burns the throat and will cause muscular contractions.. The Romans were notorious at using monkshood in the drinks of their political enemies.

Deadly nightshade (atropa bella-donna)

This plant is extremely poisonous if ingested, it often exists near brambles and has black berries which may sometimes be eaten by children can lead to eye dilation, rapid pulse and breathing difficulties.

Lily of the valley (convallaria mveryajalis)

The attractive but poisonous flowers and seeds can cause cardiac arrest and irritation.

Leland cypress (Cupressocyparis)

Leylandii are the biggest cause of nuisance claims between neighbours but their sap is an allergen, a problem if these are being pruned. If burnt the smoke can also be allergic for skin contact. Any one allergic to fabric sticking plasters are very likely to be effected by this tree. The resulting dermatitis can be serious. It is usually caused when carrying out severe pruning, which is often required because of the tree’s rapid growth. Other conifers may give the same reaction.


Contact  with the leaves and stem can cause skin irritation or even allergic reaction.

Morning Glory

This plant have=s bright bus flowers which come out in direct sunlight and close up every evening and can be a stunning display. The seeds are a poison and can cause hallucinations.

Fox glove (Digitalis purpurea)

A poisonous plant, if burnt its smoke if inhaled can lead to nausea, abdominal pain, diarrhoea, erratic pulse and vomiting. It has a strong taste which usually is enough to stop anyone ingesting its leaves, but sometimes is mistaken for the herb comfrey.


Working with the bulbs may cause an allergic skin reaction in some people.

Castor Oil Plant (Ricinus Communis)

Although the oil has many health benefits the plant itself can be poisonous, with its seeds having a high concentration of toxic. Prolonged contact with the leaves and seeds can cause irritant and allergic dermatitis. Ingestion (possibly via poor hand hygiene) can target the circulatory system.

Yew (Taxuc baccata)

All species of yew are poisonous, strangely with the exception of the red berries (see picture). The toxins can cause respiratory problems and heart attacks.


All of the plant is harmful but the seeds and pods are the parts which usually present a problem.











This warning is given for the plants with a relatively high hazard rating. Where bed labels or other promotional material is used, the warning text should appear on the bed label or other promotional material as well as on the label.


Toxic if eaten

These plants are poisonous. Even quite small quantities can be harmful. Often the whole plant is poisonous, although it is usually berries or seeds which are eaten. Children are most at risk from accidental poisoning, especially the under five age group, who may find berries and other plant parts attractive to eat. However, a remarkable number of adults also are poisoned through mistakenly identifying the plant as something edible. Daffodil bulbs are often mistaken for onions.



Harmful if eaten

These plants contain poison but pose less risk. If part of such a plant is eaten, it is advisable to seek medical advice.


Skin irritant

These plants may cause skin reactions on handling. Symptoms often include dermatitis-type reactions, local inflammation, itching and blistering. Sometimes this is only temporary and of no lasting importance, such as the well-known ‘hyacinth itch’, but in some cases reactions can be very severe. Skin irritation from daffodils and tulips is usually associated with extensive handling of the cut flowers.


Eye irritant

Eye irritation is caused by sap getting into the eye, by splash, or through wiping the eye with a contaminated finger. There  are a few cases where the irritation is caused by minute hairs brushed off the plant surface.


May cause skin allergy

Skin allergies affect only certain people. Repeated exposure to a plant may cause a skin allergy to develop. Once a person becomes allergic to a substance, they usually remain sensitive to it. The substance causing the allergy may be found in several plant groups. The person may then become sensitive to all the plants simultaneously.


Severely toxic to skin with sunlight

A small number of plants have sap which renders the skin excessively sensitive to strong sunlight. Contact with the plant followed by exposure to sunlight results in very severe localised sunburn with blistering and may cause long-lasting skin discolouration.


Harmful via skin

The toxins in such plants do not cause skin problems but can pass though the skin to organs such as the heart where they can cause disorders.


Concluding thoughts


It is important that if your staff can come into contact with plants or plant material that the risks have been assessed and particular attention paid to employees who already have any allergies.