Ranunculus acris
giant buttercup, common buttercup, tall buttercup
Hairy plant up to 1 m tall, arising from a stout rhizome. Base leaves on long petioles that are deeply divided into 3 - 7 segments. The upper leaves have short to no stalks and are smaller than the basal leaves. Flowers are up to 25mm in diameter, with round hairy flowering stalks and hairy sepals.
Other buttercups (most are probably poisonous).
Although once common in the UK where it comes from, this buttercup is rare in the N. island and only locally common in the S. island.
Although there are no reported poisonings in NZ the plant contains ranunculin in higher concentrations than many other buttercups. Ranunculin is a glycoside that forms the irritant toxin protoanemonin which is unstable and polymerises to crystalline nontoxic anemonin. Toxicity is low as the production of protoanemonin deters most animals from ingesting sufficient amounts. Protoanemonin causes erythema and blistering of the skin. All parts of fresh plants are poisonous. Toxic levels are the highest in spring, at flowering.
Grazing animals. Animals tend not to eat buttercups in pasture unless desperate.
In most domestic animals (cattle in particular), poisoning produces an excessive flow of saliva, soreness (sometimes with ulceration) of the mouth, and abdominal pain. In severe cases, this is followed by diarrhoea, with the passage of black faeces, and blood stained urine. Animals will become weak and stagger and show impaired hearing and sight. Some animals will die and death is preceded by severe convulsions
Lesions of mild to severe gastroenteritis, and possibly mouth and throat lesions, are usually seen in animals that die from buttercup poisoning. The rumen usually contains massive amounts of buttercup and mouth and throat lesions may be seen also.
History, clinical signs and evidence of ingestion.
Mild purgatives and demulcents may be give and potassium permanganate is said to be useful to protect the mouth and gut against the affects of protoanemonin. However, most mild cases do not need treatment.
Most mild cases recover spontaneously without treatment.
Connor, HE, The Poisonous plants in New Zealand, 2nd ed.,1977, Government Publications Ltd., Wellington
Parton K, Bruere A.N. and Chambers J.P. Veterinary Clinical Toxicology, 3rd ed. 2006. Veterinary Continuing Education Publication No. 249
