Marsh parsley

Cyclospermum leptophyllum, commonly called marsh parsley or slender celery, is a small annual herb of the family Apiaceae reaching just over half a meter in height. From a slender taproot arise erect, branching, hairless stems bearing soft, threadlike green leaves divided into thread-fine linear segments only a few centimeters long, giving the plant a delicate, almost fennel-like appearance. The tiny white flowers are arranged in compact, sessile or short-stalked compound umbels in the leaf axils and at the stem tips, producing small ovoid ridged schizocarps as fruits. A cosmopolitan weed of warm temperate to tropical lowlands, it occupies damp roadsides, gardens, and disturbed soils worldwide and is regarded as a noxious weed in many regions.