Vast Hogweed Species (Heracleum mantegazzianum)
Giant hogweed, a towering biennial plant, has established itself as a persistent invasive species in several states across the US. First recorded in the country in 1917, it has since spread to rich, moist soils along roadside ditches, stream banks, vacant farmland, and fence and tree lines, particularly in Pennsylvania and New York.
The plant, which can reach heights of up to 5 meters, is easy to confuse with other species in the same family, including cow parsnip, wild carrot, and common pokeweed. However, it is cow parsnip that bears the closest resemblance. Giant hogweed can be identified by its large compound umbel of white flowers, large, deeply incised leaves, and prominent white hairs and purple blotches on its stems.
One of the most concerning aspects of giant hogweed is its sap, which contains furocoumarins. This compound can cause a skin reaction known as phytophotodermatitis, a condition that causes skin sensitivity to sunlight, resulting in severe burns and blisters. Moreover, the sap can cause temporary or permanent blindness when it comes into contact with skin or eyes.
Controlling giant hogweed requires continuous management, as the plant lives for several years but dies once it flowers and bears fruit. Multiple applications per year for consecutive years may be necessary to completely control a giant hogweed population with herbicides. Triclopyr and glyphosate (Roundup and many other products) are effective herbicides for controlling giant hogweed due to their systemic activity.
Control practices also include digging, mowing, cutting, removal of umbels, grazing, and public education. Many states, such as Ohio, have implemented control programs involving public education, reporting systems, and removal efforts to manage Giant hogweed, which is primarily found in northeastern and urban areas but is spreading gradually to other parts of the state.
Research indicates that five years of intensive management is required to attempt to eradicate giant hogweed. This is due to the plant's extensive tap root, which develops during its first season of growth, and its ability to produce up to 20,000 seeds. Stream bank areas have the greatest potential to produce large infestations of giant hogweed.
Since its inclusion on the Federal Noxious Weed list, over 2,500 sites covering 20 acres of giant hogweed have been identified in 16 states. It is crucial for the public to be aware of this invasive species and report any sightings to local authorities to help in its control and eradication efforts.
){kind=link}