Extermination of the toxic, aggressive weed is a priority for the Maryland Department of Agriculture, which reports 21 known sites of the plant, mostly in the western reaches of the state but also in Harford and Baltimore counties. Workers wearing gloves, goggles and protective clothing remove the plant and treat the site with herbicides. Hogweed usually succumbs after three years. For almost a decade, the MDA has been monitoring Gunpowder Falls, "making sure no new plants are coming up" from seeds washed down from treated sites, said Dick Bean, weed management program manager for the MDA.
"The plant poses minimal risk to human health since it is mostly located behind a fence and off of the walking path," said biologist Laura Washington of the District's environmental department, but "nearby pedestrians can potentially transport the seed to other areas" if the seeds get caught in the tread of their shoes. The weed hasn't yet been found in Rock Creek Park, but the National Park Service is aware of a patch on private property near Glover-Archbold Park, according to Ana Chuquin, a Park Service biological technician.
Not every culture is an enemy of Heracleum. Iranians pickle young shoots of the plant and grind the nontoxic seeds of several species of hogweed to make golpar, a mildly bitter spice used in salads, stews and soups. In Iran, the aromatic seeds were once placed in coffins to help mask the stench of death.
Giant hogweed is a phototoxic
plant. Its sap can cause phytophotodermatitis (severe skin inflammations)
when the skin is exposed to sunlight or to ultraviolet rays. Initially, the
skin colours red and starts itching. Then blisters form as it burns within 48
hours. They form black or purplish scars that can last several years.
Hospitalisation may be necessary.
Presence of minute amounts of sap in the eyes can lead to temporary or even
permanent blindness. These
reactions are caused by the presence of linear derivatives of furocoumarin
in its leaves, roots, stems, flowers and seeds. These chemicals can get into
the nucleus of the epithelial cells, forming a bond with the DNA, causing the cells to
die. The brown colour is caused by the production of melanin by