Fineleaf Water Dropwort (Oenanthe aquatica), fam. Apiaceae.
Like Water Mint, this plant initially grows in the deep of river or lake water. Eventually its shoots with leaves outgrow the surface. The leaves of Fineleaf Water Dropwort are extremely elegant and decorative, outstripping all other Apiaceae (Celery) family members growing around Kyiv with fine lacy dissection, and only comparable with some ferns. Blooming starts in the end of June. By that time, the water level drops so much that the plants appear ashore, and their late leaves are not so striking with unusual shape. White complex umbels are not very showy, too. The seeds ripen in autumn, and the plant dies. Next year, the young generation plants will bloom – those which sprouted from seeds during the past spring and summer.
The plant is very poisonous, and while someone would have used its part in medicine, modern science does not approve such use.