Heracleum mantegazzianum Sommier & Levier
Plant height 1.5-5 m. Flowehead (umbel) width 50 cm.
This is a giant which grows taller than a man, has leaves longer than an arm, and white flower umbels larger than dinner plates. The thick stems have purple-red blotches on them.
A word of warning – do not touch it because it will seriously burns, blister and cause rashes. The sap contains furocoumarin, which if it gets on the skin makes it extremely sensitive to sunlight (phytophotodermatitis). A person can suffer phytotoxicity for months or even years.
It flowers June to July, and may be found on woodland margins, in grassy places, hedgerows, along rivers, amongst other places. An invasive species, it originates from the Caucasus Mountains and Central Asia, and was introduced into Britain and Europe in the nineteenth century. It was planted as an ornamental in gardens, but soon escaped and became naturalised. Widespread and occasional throughout Britain.