Giant Hogweed has tall stems of 2-3m terminating in umbrella-like formations of flowers. It originated in south-west Asia and was introduced to Britain in the 1800s as an attractive garden plant. It has spread rapidly since, even though restriction measures have been taken. When it grows densely in an area it shades and outcompetes local species, reducing biodiversity. It produces phototoxic sap which can cause severe burns to human skin, and this makes its removal difficult. This plant has recently been in the media after there were reports of young children being burned while playing outdoors. It was recorded in the River Thame catchment at Albury Wood and Pond in 1985.