Potentially poisonous garden plants to watch out for

Val Bourne / 18 February 2015

Some of the plants commonly found in our gardens have toxic properties which may be useful in medicine but can prove deadly if eaten. Read our tips for plants to avoid and precautions to take.



Quite recently a young professional gardener, in very good health, died a day or so after he cut down some aconitum stems in a garden. It’s a grim reminder that some of our garden plants are highly toxic.

Aconitum, or monkshood, has cowl-shaped flowers that resemble a monk’s habit. However this plant’s other common name, Wolfbane, indicates that there’s enough poison to kill a wolf and if you see the word bane in a common plant name it’s a dangerous plant.

Aconitums have been known for being toxic for centuries and their Anglo Saxon name was ‘thung’ a word that means poisonous. It may even have got its Latinised name from the Greek word Akon, meaning dart, because it’s highly possible that this plant (which is poisonous in root, stem, leaf and flower) was used to coat the tips of spears and arrowheads in the days when wolves roamed freely.

The buttercup family

The aconitum is a member of the buttercup family, or Ranunculaceae, and this family includes hellebores, clematis, trollius, delphiniums, thalictrums and aquilegias.

Their sap contains unpleasant alkaloids and glycocides that can suppress the nervous system, although none are as toxic as the aconitum.

Small amounts have been used medicinally by herbalists and many toxic plants, used in tiny amounts, have a long medicinal history.

Grazing animals always avoid buttercups and their toxicity is protection from grazing animals.

Foxglove

The foxglove or digitalis, was used by herbalists in the same way to treat dropsy and heart conditions. The extracted substance, digitoxin, has been used since 1745, and its use was written about by William Withering, a doctor from Wellington in Shropshire, who wrote An Account of the Foxglove and Some of its Medical Uses: with Practical Remarks on Dropsy, and Other Diseases in 1785. He obtained the information from a lady herbalist, also from Shropshire, who had successfully treated patients with dropsy - a lung condition.

Withering proved that an infusion of the leaves could slow and strengthen the heartbeat, which in turn stimulated the kidneys to clear the body and lungs of excess fluid. He also showed that foxglove leaves could be used in the treatment of heart failure, but that high doses could stop the heart.

This important publication in English (rather than scholarly Latin) is the first to describe the therapeutic effects of a drug and many consider his work to be the start of modern pharmacology.

Comfrey - a case of mistaken identity

Cases of foxglove poisoning occurred on several occasions when the leaves were mistaken for comfrey leaves, which do look similar. Comfrey (Symphytum officinale) was another herbal remedy used for broken bones.

The sticky root was mashed up and made into a poultice and the practice was still being used during the American Civil War (1861-1865). The common name of knitbone summed up the process and it’s been proved that comfrey does have healing powers. Other healing herbs in the garden include:

Wound-healing plants

Achillea is a wound healer which halts the flow of blood. Common named include Staunch grass and Soldier’s woundwort. Wort, an Anglo Saxon word, indicates a healer. In days gone by gardens were full of plants used in the kitchen to flavour food, used in the household as cleansers or insect repellents, or used to treat common ailments.

Superstitions

If a plant was very potent it became subject to superstitions and the peony is a plant with such a powerful reputation as a cure-all that people feared to dig it up in case evil befell them. The plants is named after Paeon, the Greek physician of the gods, and Theophrastus( 371 - 287 BC) referred to the plant’s magical properties. If you were seen near this all-powerful plant in daylight, especially if you were trying dig it up, a woodpecker would peck out your eyes.

Pliny faithfully reiterated this in his Naturalis Historia and it is still the stuff of legend. In reality it’s fine to move peonies, although October is best. It’s essential to get the tubers just two inches under the soil. Bury them any deeper, though, and they will refuse to flower.

Poisonous seeds

Castor oil (Ricinis communis)

The seeds contain a substance called ricin. When purified it can kill an adult human. This tropical looking plant, often used in ornamental bedding, is best avoided by all gardeners.

Laburnum (Laburnum anagyroides)

The golden chain tree was a highly popular garden tree and it’s still found in many gardens. It forms pods and the seeds have been ingested by children and pets and they can kill. I cut one down in a garden I had so that my children wouldn’t come into contact with it.

Runner bean (Phaseolus coccineus)

When runner bean seeds become mature and dry out they become toxic in order to discourage animals and birds from eating the seeds. You would have to eat many of these seeds to come to harm, however. They will cause upset stomachs, unless cooked.

Apple pips (Malus domestica)

Apple seeds do contain a small amount of cyanide, which is a lethal poison, but the hard seed coating prevents serious problems.

Poisonous bulbs

Bluebells (Hyacinthoides non-scripta)

All the plant parts contain glycosides and are poisonous. The sap can cause contact dermatitis. Cattle, horses and dogs have been reported to suffer digestive problems after eating bluebell leaves.

Snowdrops and Daffodils (Narcissus and Galanthus species)

Snowdrops are also toxic and can cause nausea, diarrhea and vomiting if eaten in large quantities. Narcissus bulbs will also make you ill. Both contain an alkaloid called galanthamine which is used in small doses in the management of Alzheimer’s disease.

Autumn crocus (Colchicum autumnale)

This meadow saffron has more or less been eradicated from English pastures because it can poison cattle. The active ingredient, colchicine, are highly toxic to people and animals.

Berries and fruits

The following fruits and berries should never be eaten.

Cuckoo pint (Arum maculatum)

Holly berries (Ilex aquifolium)

Elderberries (Sambucus nigra)

Spindle tree (Euonymus europaeus)

White bryony (Bryonia dioica)

Ivy (Hedera helix)

Conkers (Aesculus hippocastanum)

Cherry laurel (Prunus laurocerasus)

Yew (Taxus baccata)

Sensible precautions for avoiding poisonous plants

In the garden setting it’s always wise to wear gloves when gardening.

Always wash your hands afterwards.

Educate young children from an early age, because their size makes them more vulnerable. Toddlers and babies on the move instinctively put things in their mouths, but they have highly developed taste buds and will often spit things out. This is a defence mechanism and it’s also why young children hate Brussels sprouts.

If a child becomes ill, or you feel ill after handling a plant, do consult a doctor and give them the name of the plant.

The opinions expressed are those of the author and are not held by Saga unless specifically stated.

The material is for general information only and does not constitute investment, tax, legal, medical or other form of advice. You should not rely on this information to make (or refrain from making) any decisions. Always obtain independent, professional advice for your own particular situation.