celery-leaved buttercup - CELERY-LEAVED BUTTERCUP; celery-leaved buttercup - The smallest-flowered Buttercup of wet places, with pale yellow petals no bigger than the turned-down sepals. A pale green, usually hairless, upright, often bushy annual, 6-18 in. high, with stout hollow stems; shiny, deeply lobed, toothed root-leaves; and narrower, less divided stem-leaves. Fruits numerous, small, hairless, in an elongated head. Habitat: Widespread and fairly common in muddy places. May-September.