If You See This Plant Growing Nearby, Whatever You Do Don’t Touch It!

Giant hogweed (close-up)

Plants are a wonderful fragrant and colorful decoration on the Earth, but they can also be very dangerous for humans. This might come as a surprise, but there are only about 10 plants in North America (not including fungi) that kids need to be taught to keep away of.  

Interestingly enough, the giant hogweed is part of the carrot family, but instead with nutrients and vitamins, it is loaded with deadly toxic sap!

Heracleum mantegazzianum, commonly known as giant hogweed, cartwheel-flower, giant cow parsnip (or giant cow parsley), or hogsbane, is a plant in the family Apiaceae. In New Zealand, it is also sometimes called wild parsnip, or wild rhubarb. It typically grows to heights of 2–5.5 m (6 ft 7 in–18 ft 1 in). On the outside, it resembles common hogweed (Heracleum sphondylium, Heracleum sosnowskyi) or garden angelica (Angelica archangelica). It is phototoxic and it is considered to be a harmful weed in many regards. Giant hogweed is native to the Caucasus region and Central Asia. It was introduced to Britain as an ornamental plant in the 19th century, and it has also spread to many other parts of Europe, the US and Canada.  

The toxic sap of the giant hogweed causes phytophotodermatitis  in humans, resulting in painful blisters, long-lasting scars, and even blindness if it comes in close contact with eyes. These serious reactions are due to the furocoumarin derivatives in the leaves, roots, stems, flowers, and seeds of the plant.

Botanical description of the giant hogweed

Giant hogweed has a stout, bright green stem that is frequently spotted with dark red and hollow red-spotted leaf stalks that produce sturdy bristles. The stems grow to more than 2 m high.  The hollow stems vary from 3–8 cm (1.2–3.1 in) in diameter, occasionally up to 10 cm (3.9 in). Each dark-red spot on the stem surrounds a hair, and large, coarse white hairs occur at the base of the leaf stalk. The plant has deeply incised compound leaves which grow up to 1–1.7 m (3 ft 3 in–5 ft 7 in) in width.

Giant hogweed is a biennial or monocarpic perennial- these plants are dying after they have set seed. It usually flowers in its second year from late spring to midsummer, with numerous white flowers clustered in an umbrella-shaped head that is up to 80cm (31 in) in diameter across its flat top. The plant produces 1,500 to 100,000 flattened, 1cm long, oval, dry seeds (0.39 in) that have a broadly rounded base and broad marginal ridges. Tall dead stems may mark its locations during winter.

Identification and visible differences between giant hogweed and cow parsnip

Heracleum maximum, cow parsnip, (also known as Indian celery, Indian rhubarb or pushki) is the only member of the genus Heracleum native to North America.  It is very common in Newfoundland, Quebec, and northern Ontario, and it is often misidentified as giant hogweed.

The leaves of cow parsnip are very large, up to 40 cm (16 in) across, and divided into lobes.

The similar, but harmless cow parsnip, has green (usually) to purplish (rarely) stems that are ridged but unspotted, and covered with fine white hairs. Just like the giant hogweed, it can be large, reaching a height in excess of 2 m (6 ft 7 in). The giant hogweed flowering heads (compound umbels) branch frequently, forming clusters of several flowering head more than 80 cm (31 in) across.

Remember: A plant can be identified as the giant hogweed by checking the stems, which are green with obvious purple blotches (patches) that are a bit hairy with stiff white hairs.

Introduction of giant hogweed to Western Europe and North America

Distribution of giant hogweed in Europe (2005)

Giant hogweed was among many foreign plants introduced to Britain in the 19th century as an ornamental plant. It is now widespread throughout the British Isles, especially along riverbanks. By forming dense stands, they can displace native plants and reduce wildlife habitats. It has also spread in the northeastern and northwestern United States, and southern Canada. It is equally a pernicious invasive in Germany, France, and Belgium, overtaking the local species.

In Canada, the plant has been sighted in British Columbia, Alberta, Saskatchewan, Ontario, Quebec, New Brunswick, Nova Scotia, and in isolated areas of Newfoundland. It has been seen in Quebec since the early 1990s. The plant’s spread in Ontario began in the southwest and was seen in 2010 in the greater Toronto area and Renfrew County near Ottawa.

The giant hogweed was introduced into New York about 1917, and was recorded in British Columbia in the 1930s. It now occurs in the west in British Columbia, Washington, and Oregon and in eastern North America from Newfoundland and Nova Scotia west to Ontario and Wisconsin and south to Indiana, Maryland, and New Jersey. It is also seen occasionally in Michigan. For the reasons described above, it is a federally listed noxious weed in many states.


The sap of the giant hogweed plant is phototoxic: when the contacted skin is exposed to sunlight or to ultraviolet rays, it can cause phytophotodermatitis (severe skin inflammations). Initially, the skin colors red and starts itching. Blisters form as it burns within 48 hours. They form black or purplish scars that can last several years. Hospitalization of the affected person may be necessary. The presence of small amounts of the toxic sap in the eyes can lead to temporary or even permanent blindness.

These reactions are caused by the presence of linear derivatives of furanocoumarin 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 color is caused by the production of melanin by furocoumarins.

The results of merely brushing up against it are horrifying. If you accidentally break a stem ,or touch any of the toxic sap, you will begin to develop grotesque blisters! And due to the height of the stalk this is easy to happen!


Warning: If you come into close contact with the plant’s sap you can expect severe blistering, possible blindness if the sap comes into contact with your eyes, and possible third degree burns.

These effects come from the type of chemicals that it contains.  When these chemicals come in contact with human skin they dramatically increase the skin’s sensitivity to light. This can cause blisters that are actually very painful and form within around 48 hours and can last from anywhere between a few months to 6 years.  It can cause LONG TERM SENSITIVITY to light if the sap gets in the eye.

Measures to take if you or your child comes in contact with giant hogweed

Obviously you want to avoid it in the first place, but what if you happen to come in skin contact with the giant hogweed?

Authorities advise that children should be kept away from giant hogweed, that protective clothing, including eye protection, should be worn when handling or digging it, and that if skin is exposed, the affected area should be washed thoroughly with soap and cold water and the exposed skin protected from the sun for several days.

  • Make haste because the toxic reaction may begin within only 15 minutes and make sure you get out of the sun immediately!
  • Apply a safe sunscreen (suntan lotion) on the affected area ASAP. In the unfortunate event when the sap comes in contact with the eyes, immediately flush out eyes with water extensively. Then be sure to wear sunglasses for protection!
  • Recently some states made public warnings after these plants were spotted. In recent weeks, New York State’s Department of Environmental Conservation and the state of Massachusetts have issued detailed public warnings about the plant and the serious problems caused by coming in contact with it. These 2 states are not alone. In the northeastern region, Vermont, New Hampshire and Maine are all reporting sightings of the plant. Maryland, Virginia, Ohio, Pennsylvania and Michigan are sending out warnings. Out west, Oregon and Washington have seen giant hogweed spreading.


Currently, kids around the world are too busy preparing for tests and examinations rather than acquiring practical, hands-on knowledge such as how to identify poisonous oak or even worse – giant hogweed!

They should teach this at schools, but unfortunately, just like most important life skills, it is up to us to educate our children and each other. The plant is called giant hogweed and the pretty white flowers can be quite alluring to be picked up, but WHATEVER YOU DO, DO NOT TOUCH IT!

KIDS ARE ESPECIALLY IN DANGER due to their curiosity! So, tell them the saying, ‘Curiosity killed the cat’ to warn them of dangers like this one.


If you do spot the giant hogweed you have the option to report it to the EPA (US Environmental Protection Agency) hotline – 1-800-424-8802 FREE or your individual state agency as suggested.

Officials warn not to remove the plant by yourself or you may risk spreading seeds and getting injuries!

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