Caltha palustris
king cup, cowslip (nb, some species of Primula are more commonly called cowslip)
Looks like a large celandine. Up to 60cm high, heart shaped leaves about 10x15cm, yellow flowers about 30mm diameter and spiky fruit. Only grows on edges of water.
Closely related to the buttercups (not marigolds). The native korikori (Ranunculus insignis) is very similar and probably toxic, but only grows in alpine meadows where stock are unlikely to come across it.
Occasional escape from gardens along streambanks.
The plant may contain protoanenomin, although marsh marigolds are reported to contain much less than buttercups. Protoanemonin 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.
No reports from NZ, mainly cattle overseas.
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.
Acute inflammation of the stomach and intestines. Mouth and throat lesions. Rumen contents may contain a large amount of buttercup. Renal damage is sometimes evident.
From history, clinical signs, post mortem findings.
Mild purgatives, demulcents. Potassium permanganate protects the skin from irritant action of protoanemonin.
Fatal poisoning rare.
Selective weedkillers. Beware wilted plants may be more palatable than fresh ones.
Conner H.E. The Poisonous Plants In New Zealand. 1992. GP Publications Ltd, Wellington
Cooper M R, Johnson A W. Poisonous Plants and Fungi in Britan: Animals and Human Poisoning. Her Majesty’s Stationary Office. London. 1998
4 October, 2007
