Oenanthe crocata aka Hemlock Water Dropwort

Oenanthe crocata is a herbaceous perennial in the Apiaceae family. Its common names include hemlock water dropwort and balder root. It grows in temperate regions and is native to Madeira. Its range also spans western Europe and the western and central Mediterranean. It is native to Britain and Ireland. Wild plants grow in damp meadows and beside ditches and ponds.

This clump-forming plant reaches about 3.3–4.9 feet (1–1.5 m) tall. Its spread reaches about 4.9–8.2 feet (1.5–2.5 m). It can take two to five years to reach full size. Below ground, it forms long root tubers. Its upright stems are hollow and marked with grooves. The leaves are pinnate, with leaflets arranged along a central stalk. The foliage is deciduous, so the plant does not keep its leaves year-round.

White flowers form umbels during July and August. Each flowerhead spans about 2–4 inches (0.05–0.1 m). These summer blooms stand above a plant with a broad footprint. Allow for its full spread when judging a planting site. The RHS lists it for wildlife gardens and bog settings. Yet its presence beside water does not make it harmless. Its severe toxicity is a key concern wherever people or pets have access.

The RHS gives full sun as its preferred position. It lists clay and loam as suitable soils. The ground should stay wet, with poor drainage. Acid, neutral, and alkaline soils all suit it. A sheltered site is preferred, with east, south, or west exposure. Its H7 rating indicates hardiness below −4°F (−20°C). This makes it hardy through the coldest European continental winters. Seed is the listed means of propagation. The RHS says it needs no pruning.

This species can become a nuisance when left unchecked. Its broad spread deserves attention even in a suitable wet site. The RHS reports few usual pest or disease problems. The greater risk comes from poisoning, not poor plant health. Hemlock water dropwort is extremely poisonous if eaten. It also poisons dogs that eat it. Do not treat any part as food. Wear gloves and other protective equipment when handling the plant. Its wildlife-garden use does not lessen these hazards.