This section is from the book "A Guide To The Poisonous Plants And Weed Seeds Of Canada And The Northern United States", by Robert Boyd Thomson, H. B. Sifton. Also available from Amazon: A guide to the poisonous plants and weed seeds of Canada and the northern United States.
Other Common Names: Biting Crowfoot, Celery-leaved Crowfoot, Blisterwort.
This plant is the most poisonous member of the genus Ranunculus. Its juice has an extremely acrid, volatile constituent, strong enough, it is said, to produce a blister if placed in contact with the skin for two minutes. In Europe, professional beggars used the plant for produc: ing sores and ulcers, to excite pity and obtain gifts. The plant is found in low lands throughout the continent, but, needless to say, is seldom eaten. It has, however, been held responsible for much trouble, especially in cows, producing, according to Cornevin, colic and diarrhoea with attempts at vomiting, accompanied by a falling off in milk and various nervous symptoms. In serious cases convulsions are produced, followed by death in six to twelve hours. Similar symptoms are produced in horses. Willing says that treatment should be symptomatic, and that tannin is advisable.
Fig. 33. - Cursed Crowfoot - Ranunculus sceleratus.
The plant, which blooms from June to August, is an annual, one-half to two feet high. The thickish leaves are three-lobed and toothed, the radical with long petioles and those of the stem sessile or with shorter stalks. The flower is typical of the family, with five sepals, five petals of equal length, and numerous stamens and pistils, the latter forming an oblong head when ripe. The flower is about one quarter of an inch broad, and pale yellow.
The Common or Tall Buttercup, Ranunculus acris L., is plentiful in pastures east of the prairies and is found also in British Columbia. Its effects resemble those of Ranunculus sceleratus but are not nearly so pronounced. Animals avoid it, but naturally, in pastures where it is plentiful, small amounts are sometimes eaten, and in such cases it has been blamed for causing sporadic abortion in cows. As in all other members of the genus, the poison is volatile, and when dried in hay the plants are harmless.
The Tall Buttercup is a perennial, somewhat hairy plant, two to three feet in height and conspicuous on account of the abundant bright yellow flowers sometimes an inch in diameter. The sepals are small, pointed, and hidden by the spreading, rounded petals. The leaves are three to seven-parted, and deeply lobed. The root leaves are larger and more lobed than the stem leaves, and are provided with long petioles.
The Small Flowered Crowfoot, Ranunculus abor-tivtu L., is acrid, and causes blistering. It is a smooth plant one-half to two feet high. Its root leaves are petioled, round, heart-shaped or kidney-form and crenately lobed, and the stem leaves sessile or nearly so, with linear lobes. The flowers are very small, the yellow petals being no longer than the reflexed sepals. It has a fruiting head like that of Ranunculus sceleratus but smaller.