8 toxic perennials

Aconite

All species of Aconite are poisonous. They are a deadly poison for humans and many animals. Even some of their common names are ominous: “Wolf’s bane” or “Strangle-wolf” for Aconitum vulparia, “Poisonous Aconite” for Aconitum anthora, or “Jupiter’s helmet” for Aconitum napellus. These plants are primarily found in mountainous regions but are also cultivated in gardens. Notably, you can find:

• Aconitum napellus or Monkshood and Aconitum napellus ssp. vulgare or Common Monkshood, which display their tall blue-violet spikes in summer
• Aconitum lamarckii or Lamarck’s Aconite, a perennial cultivated in gardens and very common in the wild flora of the Pyrenees
• Aconitum carmichaelii x cammarum ‘Pink Sensation’, a beautiful, very hardy tuberous perennial blooming from August to October in long panicles of light pink flowers
• or the rarer climbing Aconite Aconitum hemsleyanum ‘Red Wine’

Aconitum napellus

Active Principles, Toxic Parts, and Effects

Aconites contain powerful cardiotoxic alkaloids, notably aconitine and aconine. The most toxic parts are the fleshy roots or tubercles: ingesting 12g of roots could be fatal for a human. However, all parts of the plant are very dangerous: merely holding an Aconite flower in the mouth for a few minutes is enough for the first symptoms of burning to appear.

Foxglove

Foxgloves prefer to grow in cool soil, in clearings or at the edge of woods and forests. These are perennials that form elegant, tall floral stems in soft shades ranging from purple to yellow, including white and apricot. The most well-known is the Digitalis purpurea. Requiring little maintenance, they tend to self-seed spontaneously and are perfect for natural-style borders or cottage gardens, where they add structure and verticality to displays.

However, foxgloves can be very toxic. Their powerful action on the heart means they are used in the formulation of cardiotonic medications.

Digitalis purpurea

Active Principles, Toxic Parts, and Effects

All parts of foxgloves are toxic, particularly the leaves. Depending on its exposure to sunlight, each plant contains varying doses of active principles. The purple foxglove (Digitalis purpurea) and the woolly foxglove (Digitalis lanata) are well known for their high toxicity as they contain cardiotonic substances (heart stimulants), particularly digitalin, but other spontaneous or horticultural hybrid species are also dangerous. The leaves of the purple foxglove can be confused with those of borage or comfrey, both of which are edible.

According to literature, ingesting around ten leaves of purple foxglove can cause serious disorders in an adult, and 120 g of purple foxglove leaves represents a lethal dose. The first symptoms of poisoning are:

• nausea and vomiting,
• diarrhoea,
• cardiac disturbances.

Hellebore

With their delicate flowering blossoming in the heart of winter, hellebores make this season a little more colourful. The earliest begin to flower in November, while the latest finish in April. They are decorative both for their stunning flowers and their evergreen foliage. There are many varieties, including the famous Christmas Rose Helleborus niger, which can display a wide range of colours. However, their name Hellebore is thought to derive from the Greek helein: “to injure” or “to kill”, and bora: “food”, which can be translated as “the food that kills”: they are indeed reputed to be toxic, like most Ranunculaceae.

Helleborus

Active Principles, Toxic Parts, and Effects

All parts of hellebores contain toxic substances (helleborine and helleborine), powerful alkaloids that affect the nervous system and the heart. Since antiquity, Helleborus niger has been cultivated for its analgesic, cardiotonic, purgative, emetic, and vermifuge properties, prescribed in minute doses to treat epilepsy or migraines. Their toxicity acts directly on the heart muscle, causing convulsions, delirium, and sometimes death. Leaves, flowers, fruits, and especially roots are highly toxic.

Euphorbia

There are around 2,000 spurge species, sometimes very different in appearance from one another. As it is not possible to cover the entire family of spurges in detail, we will approach them with caution. Their main common feature is the production of latex, a white liquid that appears when broken, which is highly toxic. Among them, Euphorbia lathyris, or Greater Spurge, stands out: its name is unambiguous regarding its strong purgative powers!

Euphorbia lathyris

Active Principles, Toxic Parts, and Effects

The latex of spurges contains highly corrosive diterpenic esters and its oil contains a colloidal toxalbumin comparable to that found in castor oil: two substances with toxicity exceeding that of strychnine. This latex causes skin irritations and is extremely dangerous in case of contact with the eyes. The seeds, which are also toxic, were once used as a purgative.

Delphinium

Also known as Larkspur or Dolphin’s Bane, Delphiniums are well-known and prized perennials among gardeners. They are commonly grown in ornamental gardens. The genus includes various species, most of which are perennials, while others are annual or biennial. Many cultivars have been selected for their majestic flower spikes reaching towards the sky, blooming from June to August and offering a wide diversity of colours, predominantly blue.

Delphinium

Active Principles, Toxic Parts, and Effects

Despite their natural and friendly appearance, do not be deceived: all parts of the plant are toxic. They contain toxic alkaloids (including delphinine), causing vomiting when ingested and even death in high doses. In low doses, extracts of delphinium have been used in herbal medicine.

In case of ingestion, various symptoms may be observed, such as excessive salivation, vomiting, diarrhoea, tingling sensations in the skin, headaches, muscle weakness, dilated pupils, and vision disturbances. A drop in blood pressure can lead to a decrease in heart rate. Finally, seizures and coma may occur. The plant is also toxic to animals.

Lily of the Valley

No need to introduce the lily of the valley (Convallaria majalis), this rhizomatous woodland perennial celebrated on 1st May. The genus comprises only one spontaneous species, introduced to gardens in Europe in the 16th century, and is valued for its immaculate flowering with an incomparable scent.

Convallaria majalis

Active principles, toxic parts, and effects

Its charming little bells conceal steroidal heterosides with properties similar to digitalis. They also contain saponins that can cause digestive disturbances. The most toxic parts are the flowers: it is advisable to avoid inhaling their fragrance for too long, and chewing the stems can lead to serious gastrointestinal and cardiac issues. The water in which your bouquet of lily of the valley has been placed is also toxic.

Datura

Cultivated as an annual, the Datura is a fast-growing perennial shrub that captivates gardeners with its large trumpet-shaped white summer flowers exuding a sweet fragrance. Sowing perennial Datura is easy; it thrives in rich, well-drained soil.

Datura

Active Principles, Toxic Parts, and Effects

All parts of the plant are toxic: it is rich in alkaloids throughout its organs, which are used in pharmacology. Even licking fingers after contact, for example in children, can be dangerous.

Datura is a psychotropic plant with unpredictable biochemical effects, ranging from panic attacks to temporary blindness, as well as delirium, amnesia, or even loss of consciousness.

Gloriosa

Also known as Glorious or Glory Lilies, Gloriosa rothschildiana and Gloriosa superba are tuberous climbing perennials native to South Africa. They display stunning, vibrant summer flowers. As quintessential tropical plants, they require warmth and humidity to thrive.

Gloriosa rothschildiana

Active Principles, Toxic Parts, and Effects

Much richer in colchicine than the colchicums themselves, all parts of the plant are highly toxic if ingested, and the tubercles are irritant. Used by the pharmaceutical industry, it contains chemical compounds such as colchicine and gloriosin, which are of interest as anti-inflammatories. It is also used in African pharmacopoeia, where its leaves are employed in the treatment of asthma, to treat lice, and against snake bites.

How to prevent the risks of poisoning

To prevent the risks of poisoning from these perennials, it is advisable to:

• of course, not ingest the mentioned plants;
• primarily admire them and only touch them when necessary (cleaning, weeding, etc.). In this case, it is strongly recommended to wear gloves when gardening among these plants and to wash your hands or any other part of your body after contact. Avoid bringing your hands to your face;
• if you choose to grow some of these toxic plants in the garden, plant them out of reach of children and pets;
• make children and anyone unaware aware of the potential dangers of these plants.

What to do in case of poisoning or contact?