Ranunculus occidentalis Nutt.

The seeds of Ranunculus occidentalis were eaten by some Californian Indians. D. E. Moerman (1986) identified this taxon as an Aleut poison: juice of the flowers could be slipped into food to poison the person who ate it.

Stems erect to reclining, not rooting nodally, hirsute or sometimes pilose or glabrous, base not bulbous. Roots never tuberous. Basal leaf blades broadly ovate to semicircular or reniform in outline, 3-parted or -foliolate, 1.5-5.3 × 2.2-8 cm, segments usually again 1(-2)×-lobed, ultimate segments oblong or elliptic to lanceolate or oblanceolate, margins dentate (sometimes dentate-lobulate or entire), apex acute to rounded-obtuse. Flowers: receptacle glabrous; sepals reflexed 2-3 mm above base, 4-7(-9) × 2-4 mm, hirsute; petals 5-14, yellow, 5-13 × 1.5-8 mm. Heads of achenes hemispheric, 3-7 × 5-9 mm; achenes 2.6-3.6(-4.8) × 1.8-3(-3.2) mm, glabrous, rarely hispid, margin forming narrow rib 0.1-0.2 mm wide; beak persistent, lanceolate to lance-subulate, straight or curved, 0.4-2.2 mm.

Ranunculus occidentalis, the western buttercup, is a species of buttercup found in the western regions of North America. Its distribution extends from Alaska through British Columbia and Alberta to central California. The flower can be seen in open meadows, forests, and other generally flat areas up to an elevation of 2,200 metres (7,200 ft).

Aleut first nations may have used juice from the plant as a poison, its toxicity arising from the substance protoanemonin. Shasta first nations coincided blooming Ranunculus occidentalis with salmon runs in the summer. The seeds were used to make pinole, a staple food.

This plant is similar to, and sometimes difficult to distinguish from, the California buttercup (Ranunculus californicus).

Wikimedia Commons has media related to Ranunculus occidentalis.