What does giant hogweed do

Flowers: appear in June and July. They are small and white or slightly pink and are clustered on umbrella-like heads known as umbels that can reach a diameter of 60cm.

All the flowers on the umbel face upwards. Seeds: dry, flattened, and oval. Look for purple blotches on stems and coarse hairs around the base of leaf stalks. In short - the sap of giant hogweed can cause burns. It contains furocoumarin, which makes skin extremely sensitive to sunlight phytophotodermatitis. If the sap gets onto your skin, then you are exposed to sun, your skin can blister badly and blistering can recur over months and even years.

This is known as phytotoxicity. The best way to avoid injury is to familiarise yourself with the plant. Avoid brushing through patches of giant hogweed and exposing yourself to plants which have been cut which might cause you to get sap on your skin. If you do get giant hogweed sap on your skin, be sure to wash the area thoroughly immediately, seek medical advice, and do not expose the area to sunlight for a few days.

Giant hogweed has deeply divided leaves which give it a jagged appearance. The leaves of common hogweed are less jagged and more rounded than giant hogweed. This is very similar-looking to giant hogweed but is much smaller. This plant only reaches a maximum height of 2 metres 6ft 7 and the symmetrical flower heads only reach 20cm across. Its seeds are much smaller and lighter than those of giant hogweed, and the leaves are less jagged and more rounded at the edges than giant hogweed.

It was later transported to the United States and Canada as a showpiece in arboreta and Victorian gardens one of the first North American plantings of giant hogweed was in gardens near Highland Park in the City of Rochester, New York. It was also a favorite of beekeepers because of the size of its flower heads the amount of food for bees is substantial.

A powder made from the dried seeds is also used as a spice in Iranian cooking. Unfortunately, as with so many invasive plants, giant hogweed escaped cultivation and has now become established in a number of areas in New York see map, below , as well as in Connecticut, the District of Columbia, Illinois, Maine, Maryland, Massachusetts, Michigan, Ohio, Oregon, Pennsylvania, Washington, Wisconsin, and Ontario and Vancouver Island in Canada.

Because of its public health hazard potential and, to a lesser extent, to its potential ecological impacts, giant hogweed is on the federal noxious weed list and several state lists of prohibited plant species. Giant hogweed Heracleum mantegazzianum is a member of the carrot or parsley family, Apiaceae Umbelliferae. Except for its size, the plant can be mistaken for a number of native, noninvasive plants such as cow parsnip Heracleum lanatum , Angelica Angelica atropurpurea , and poison hemlock Conium maculatum.

Of these, the plant most likely to be misidentified as giant hogweed is cow parsnip. A fourth, not-so-innocuous, invasive giant-hogweed imposter found throughout North America is wild parsnip Pastinaca sativa.

Information on how to distinguish these giant hogweed wannabees from the real thing can be found later in this profile. Giant hogweed is a perennial herb with tuberous root stalks. It survives from one growing season to another by forming perennating buds surviving from season to season and enduring a period of dormancy during the winter.

Numerous up to , , half inch long, winged, flattened oval seeds form in late-summer. These seeds, originally green, turn brown as they dry and can be spread by animals, surface runoff of rain, or on the wind, establishing new colonies. Seeds can remain viable in the soil for up to 10 years. The plant may grow to 15 to 20 feet in height.

As mentioned earlier, there are several plants in New York and the Northeast that can be mistaken for giant hogweed. Key features for distinguishing these plants from giant hogweed are explained below.

Click the identification tables to enlarge. Giant hogweed may grow to 15 to 20 feet in height. Stems are 1 to 3 inches in diameter, but may reach 4 inches. Stems are marked with dark purplish blotches and raised nodules. Leaf stalks are spotted, hollow, and covered with sturdy bristles most prominent at the base of the stalk. Stems are also covered with hairs but not as prominently as the leaf stalks.

Leaves are compound, lobed, and deeply incised; can reach up to 5 feet in width. Numerous white flowers form a flat-topped, umbrella-shaped head up to two and a half feet across.

Native Cow parsnip, while resembling giant hogweed, grows to only five to eight feet tall. The deeply ridged stems can be green or slightly purple, do not exhibit the dark purplish blotches and raised nodules of hogweed, and only reach one to two inches in diameter, contrasted with hogweed stems which can reach three to four inches in diameter.

Where giant hogweed has coarse bristly hairs on its stems and stalks, cow parsnip is covered with finer hairs that give the plant a fuzzy appearance. Both sides of the leaves exhibit these hairs but they are predominantly on the underside of the leaves. Native purple-stemmed Angelica is more easily differentiated from giant hogweed by its smooth, waxy green to purple stems no bristles, no nodules , and its softball-sized clusters of greenish-white or white flowers, seldom reaching a foot across.

Giant hogweed grows throughout the Grand River watershed and tends to grow in undisturbed sites with abundant light, but it also grows on the forest's edge or partially shaded areas. The plant is a perennial, meaning it returns every spring. It is originally from Asia and was brought to Ontario as an ornamental plant. Since arriving in Ontario, the plant has spread quickly, taking advantage of local waterways, including those in the Grand River watershed, to carry its particularly buoyant seeds.

Experts say the plant is becoming increasingly common throughout Ontario, growing at the edges of forest, rivers and even backyards, but it is difficult to say how widespread the weed has become. If you find the plant in your backyard, the City of Guelph recommends removing it. The weed is a public health hazard and is dangerous to both children and pets.