Hybridises with : Hogweed

Some similarities to : Hogweed but Giant Hogweed is up to twice as tall at 4 or 5 metres, the flower umbels of larger diameter up to 1m across, and the fruits are narrower. The leaves of Giant Hogweed are not only larger, up to a metre long, but differ in form being more fan-shaped, rather than having great chunks missing from the edges which is what Hogweed looks like. Uniquely identifiable characteristics : There is no other umbellifer as tall and large as this one!

Distinguishing Feature : It's is very tall, over 1.5m and it is not the knotweed Giant Knotweed.

The Flowers are white or off-white. Like as in many umbellifers, the outer petals are longer than those on the inner-facing side of flowers, especially those flowers on the outer edge of the umbel.

Giant Hogweed is a troublesome spreading weed, that proliferates especially along water-courses such as canals and especially rivers. Great efforts are being expended in trying to eradicate any out-breaks. The two clusters where the above photographs were taken have now been eliminated. Its extermination is being pursued vigorously because not only does it spread un-controllably.

Furanocoumarins are exploited medically for the treatment of psoriasis, which is somewhat surprising as you might have thought they would cause psoriasis.

Because the stems are very stiff, long and hollow, children have a propensity to play swords with them or reportedly use them as pea-shooters (although this seems unlikely given their size and girth!). Many were hospitalised in the 1980's as a result of the severe photodermatitis that ensues on subsequent exposure of the skin to sunlight. Extensive skin contact with the sap and subsequent sun-exposure can lead to death in severe cases. The sap of Hogweed and Wild Parsnip also contain much the same photosensitizing furocoumarins, and should also be handled with care (using strimmers to hack them down is not recommended!).

Giant Hogweed has but a tap root and does not reproduce vegetatively. Each plant produces up to 5000 seeds which are able to float, and being next to flowing water-courses and rivers, spread far along the banks. Eradication is not easy; it is largely un-affected by weed-killers unless the plant is very young.

ANY TEXT GOES HERE

The Furocoumarins in Giant Hogweed are Heraclenin, Heraclenol and Xanthotoxin (8-methoxypsoralen, or 8_MOP), upon which Heraclenin and Heraclenol are based. All three are photo-toxins and carcinogens.

Imperatorin is another Furanocoumarin, possibly an intermediate stage between 8-methoxy Psoralen and Heraclenol and Heraclenin.

Giant Hogweed contains exceedingly irritant chemicals in its sap. These chemicals are called Furocoumarins (aka Furanocoumarins), and cause photo-sensitisation of skin. When sap on the skin is exposed to sunlight, chemical reactions occur which cause photo-dermatitis, about 40 to 50 hours later resulting in the itching and intense reddening and formation of enormous wheals on the skin which can be troublesome to heal. The resulting darkening pigmentation of the skin and scarring lasting several years. Exposure of the skin to greater amounts of these furocoumarins can damage the kidneys and liver and can be fatal. Furanocoumarins are very dangerous substances, and, being phototoxic, cross-link with both strands of DNA in the presence of strong sunlight. This action leads to cell death by apoptosis, and also to mutation; Furocoumarins are cytotoxic. Blindness can result if any sap should enter the eye. Needless to say, these compounds are even more dangerous if taken orally.

Furocoumarins

p-Cymene (para-Cymene), also in Giant Hogweed, is a monoterpene that is toxic to animals, and yet present in a number of essential oils such as oil of Thyme and oil of Cumin. Ortho- and meta-Cymene can be synthesized in the laboratory, but the isomer para-Cymene is the only naturally occurring isomer of Cymene. It forms complexes with ruthenium and osmium.