Are rhododendrons poisonous?


I study plant biotechnology and often find myself confronted with the serious consequences that lack of knowledge and misinformation can have for nature. That is why I am so passionate about bringing people and nature closer together again.

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Are rhododendrons poisonous to humans? And what about the danger for pets like cats and dogs? We clarify everything.

Two dogs sat in front of a rhododendron
People and pets should stay away from the rhododendron [Photo: Eudyptula/]

Rhododendrons (Rhododendron) are popular evergreen shrubs found in many gardens and parks. However, just because the rhododendron can be found everywhere, it is far from harmless. Since certain substances serve as natural feeding protection for the plant, people and pets should keep their distance.

Are rhododendrons poisonous?

The flowers, leaves and fruits, as well as other parts of the plant albeit in smaller quantities, contain toxic diterpenes. Even contact with the plant can cause skin irritation. Therefore, you should always wear gloves when caring for and planting rhododendrons. Even eating one leaf or flower can cause the following symptoms of poisoning:

  • Nausea
  • Diarrhoea
  • Stomach pain
  • Sickness
  • Hypersensitivity of mucous membranes and extremities
  • Increased salivation

These are caused by the blockage of certain channels at the cellular level, which prevents the reproduction of stimuli between the cells of the gastrointestinal tract, the heart, the skeletal muscles and the nervous system respectively. In an emergency, this can lead to respiratory disorders, seizures, severe cardiac arrhythmias, paralysis or even death. A doctor should be consulted immediately if symptoms become more severe. For mild symptoms, it is sufficient to drink plenty of fluids. Nevertheless, compared to other ornamental plants, the rhododendron is not considered particularly toxic. Planting is discouraged if there are small children in the household.

Cat with a rhododendron flower
Animals experience the same symptoms as humans [Photo: ZHANGXIAOLI/]

The nectar also contains certain diterpenes called grayanotoxins. As a result, honey in some regions, such as the Turkish Black Sea coast, contains small amounts of the toxin. This Pontic honey, or Toll honey, can cause symptoms of poisoning such as nausea, vomiting and hallucinations.

Rhododendron poisonous for cats and dogs, etc?

Many dangers also lurk in the garden for the domestic four-legged friend. Thus, the toxins are also poisonous to domestic animals such as dogs and cats, horses, cattle and tortoises. The same symptoms occur as in humans, except that they are more intense and occur from a smaller amount. If you recognise any of these symptoms of poisoning, it is therefore advisable to consult a veterinarian.

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