Heracleum mantegazzianum,
commonly known as Giant Hogweed, is a non-native, invasive species in the United States, Canada and Europe. Along with being an invasive species, Giant Hogweed is also classified as a toxic species, causing large burns and blisters when a person is exposed to the sap under ultraviolet light. The tale of Giant Hogweed’s journey from Southwest Asia to England, where it has spread much more widely than it has yet here in the United States, is chronicled in the 1971 song “The Return of the Giant Hogweed” by the rock band, Genesis. In the song, the plant is depicted as an angry plant that is out to get people; they must then attack the plant at night when the plant can’t burn them. After experiencing them first hand in Athens County, Ohio, and hearing the song, Giant Hogweed was the perfect plant for this project. The song even uses the plant’s scientific name in the lyrics.
Giant Hogweed is native to Caucasus Mountain Region in Southwest Asia. Giant Hogweed’s native habitat is the Caucasus Mixed Forest, a Temperate Broadleaf and Mixed Forest in the Palearctic Ecoregion. The Caucasus Mixed Forest sits in a “biogeographical crossroads where flora and fauna of at least three biogeographic provinces converge - Central/Northern Europe, Central Asia, and the Middle East/North Africa.” (DISCOVER > Conservation Science > Ecoregions > Palearctic... [Updated 2008]
Having found its way out of that region, Giant Hogweed is now considered an invasive species in the United States, Canada and Europe. Giant Hogweed arrived in Europe in the 1800’s and has become a widespread nuisance. In the United States, distribution has been limited both by the smaller time-frame, as Giant Hogweed was first introduced in 1917, and by eradication efforts being made by neighboring states. Currently, all states outside of New York and Washington are proceeding with eradication projects. (Giant Hogweed… [Updated 2008]
Giant Hogweed can be biennial or perennial, with a deep, branching tap root. It reproduces mainly by seed, though cut stems may re-sprout. Its leaves are arranged alternately and can grow up to 10 feet (3 m) long. The leaves are pinnate, with pubescence underneath and a petiole base that is enlarged to surround the stem at the node. Stems are purple-mottled, hollow, and rigid, and can grow between 7 and 16 feet (2-5 m) tall, and up to 4 inches (10 cm) in diameter. Flowers are a compound umbel that can grow up to 5 feet (1.5 m) in diameter with 50 to 150 rays. The flowers are white and most plants flower in their third or forth year between June and August. They are pollinated by various insects, mostly bees and flies, and can self-pollinate between different umbels. The fruit is elliptic, ridged and winged 3/8 to 5/8 inches (8-15 mm) in length on elongate stalks. The stalk splits in half, each half containing one seed. One plant can produce 100,000 seeds and they are dispersed by water, wind or human, usually within 33 feet (10 m) of the mother plant. Germination requires moisture and cold stratification, and will occur in light or dark. The plant grows generally in waste places, roadsides, disturbed woodland and stream banks, but can invade a range of habitats. Studies have shown a preference to open, mesic and seasonable cold habitats. (Huebner et al. 2004)
Burns caused by the sap are attributed to compounds called Furocoumarins that when in contact with both sunlight and human skin leads to a condition known as phyto-photodermatitis. This extreme sensitivity to ultra-violet light produces swelling and blistering and can lead to permanent scarring. Contact with the eyes can cause temporary or even permanent blindness. (Giant Hogweed… [Updated 2008] Persons dealing with the removal of this plant are advised to do so at night and wear protective clothing covering the skin completely. Though the compounds deter herbivory from some generalists, specialist insect herbivory is common. Many grazing animals such as cows, sheep, goats and pigs are able to eat the plant with no ill effects. (Huebner et al. 2004)
Webpage by: Jeremy Wooddell
Part II
Temperate Broadleaf and Mixed Forests
Heracleum mantegazzianum is native to the Caucasus Mixed Forest, a Temperate Broadleaf and Mixed Forest. Temperate Broadleaf and Mixed Forests are found predominantly in the mid-latitude regions of North America, Europe, and Asia. They are characterized by a humid climate that undergoes regular seasonal temperature changes. "The typical structure of these forests includes four layers. The upper-most layer is the canopy which is composed of tall mature trees. Below the canopy is the three-layered, shade tolerant understory. The top layer of the understory is the sub-canopy which is composed of smaller mature trees, saplings, and suppressed juveniles canopy layer trees awaiting an opening in the canopy. Below the sub-canopy is the shrub layer, composed of low growing woody plants. Typically the lowest growing (and most diverse) layer is the ground cover or herbaceous layer." (Wikipedia... [Updated 2008] These areas typically receive 30 to 60 inches (75 to 100cm) of relatively evenly distributed precipitation per year. (Enger and Smith 2004)
The vast majority of the tree species present in this Biome are wind pollinated, creating large stands of the same species. This is in contrast to Tropical Forest which feature predominantly animal pollinated trees resulting in a much more spread-out, diverse population. The Temperate Broadleaf and mixed forests are home to a diverse amount of fauna as well, with a great variety of insects, birds, amphibians, reptiles, and mammals, not to mention the amount of soil bacteria and fungi present. These areas are literally teeming with life.
Throughout the world, these areas face common pressures from logging and resource extraction, as well as clearing for development due to growth in human population and urban sprawl. While proper urban planning and conservation techniques do offer ways of slowing the consumption of these areas, the exponential growth of the human population and that population's ability to exploit resources lend one to think that even though we may replant and manage these areas, they are even now and likely even further to be, pale comparisons to what were once great, thriving ecosystems. With top predators missing and old-growth stands few and far between, combined with an absence of fire, there is no doubt that these areas have been and will continue to be irrevocably changed by human hands.
On a more specific level, Heracleum mantegazzianum is native to the Caucasus Region, where this particular Temperate Mixed Forest sits in a precarious position between a number of other biomes, at the edge of a continent. The Caucasus region comprises roughly 65,800 square miles (170,300 square kilometers) -- about the size of the state of Washington. (Caucasus Mixed Forest [Updated 2008]
Currently, the Caucasus is experiencing the same developmental pressures as seen in other Temperate broadleaf and Mixed Forests. “About 5% of the region’s areas have protective guidelines.” (Caucasus Mixed Forest [Updated 2008] Protected areas are Borjomi-Kharagauli National Park, Lagodekhi and Tusheti Strict Nature Reserves in Georgia, Caucasus Biosphere Reserve in Russia, and Zakatala Reserve in Azerbaijan. (Caucasus Mixed Forest [Updated 2008]
The pressures to expand forestry in the region as well as the fact that fire wood is still the preferred fuel source for homes, lend one to believe that change is coming fast to this region. Perhaps plants like Heracleum mantegazzianum, with their invasive nature in other areas of the world, are just providing a future for themselves as best they can in a world so pressured by human activity and consumption.
References
Enger ED, Smith BF. 2004. Environmental Science:A Study of Interrelationships, Ninth Edition: New York (NY): Mcgraw Hill. p124
Huebner CD, Olson C, Smith H. 2004. Invasive Plants Field and Reference Guide: An Ecological Perspective of Plant Invaders of Forests and Woodlands: Morgantown (WV): USDA Forest Service. p. Giant Hogweed.
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