Photo by ROBERT VID@bugwood.org

Giant hogweed

Beauty or beast? Sometimes it's hard to tell

Research confirms giant hogweed is aptly named. Health and environmental authorities from coast to coast are warning folks to avoid the stuff because its sap can cause blisters, third-degree burns, scarring and, in extreme cases, blindness. They encourage people to more than avoid touching giant hogweed or even getting close enough to try killing it. Anyone who sees the devilish plant with umbrella-size flowers should call their state department of health.

It's that bad

Recognized by its towering height — stretching skyward 10 to 15 feet — giant hogweed blooms from mid-May through July. Eurasian immigrants brought it to America in the early 20th century for ornamental plantings. They considered it a curiosity because it grows so large. The flower head, shaped like an umbrella and strikingly similar to Queen Anne's lace on steroids, can measure 2½ feet across with 5-foot leaves. But this beauty is an undeniable beast that some state officials say is more like the man-eating plant from "The Little Shop of Horrors."

Once established, seeds from the alien invader were distributed to botanical gardens and homes. It's not clear if botanists knew about the plant's poison — or whether anyone cared until people began finding out the hard way. By then, giant hogweed was taking over. Now it inhabits at least 15 states including New York, Pennsylvania, New England, parts of the Midwest and the Pacific Northwest. In Canada, it grows in New Brunswick, Quebec, Ontario and British Columbia.

Like kudzu in the South, the sprawling plant is an aggressive colonizer that can smother anything in its path. It lives on riverbanks, near streams, on roadsides, in vacant lots, in yards and gardens and in cool, wet areas.
Aside from its harmful effects on people, hogweed provides poor habitat for mammals, birds, fish and insects. It shades out native plants and disrupts ecosystems because it competes with other plants for sunlight, space and nutrients. Giant hogweed starts growing in April before many native species begin to poke through the soil. It grows quickly and a single plant can produce as many as 10,000 seeds in late summer.

In the fall, dead stems can clog watercourses and lead to flooding, while roots cause riverbanks to erode and collapse. The roots also damage walls, pipes and houses. Its costly and destructive characteristics landed hogweed near the top of the federal government's noxious weed list.

"We consider it a major target," Alan Tasker, who manages the list, said on the U.S. Department of Agriculture's website.

Strong herbicides can help control hogweed.

Hogweed sap can cause blisters, burns,
scarring and blindness.

Buying hogweed commercially and hauling it from state to state, or even within the same state, are illegal. Such laws help keep humans from contributing to the spread of the noxious plant. Nature is much harder to control, since birds, waterways, soil and compost carry the seeds, which are viable up to 10 years after they've been deposited.

In New York, the weed is so rampant the state's Department of Environmental Conservation established a giant hogweed hotline and ordered a 14-person crew to root out nesting spots along streams, roads and backyards. Plants can be attacked either by digging up their roots or spraying heavy doses of herbicides. Either method is a long-term effort.

According to Naja Kraus, the DEC's giant hogweed program coordinator, each plant takes three or four years to store enough energy in its roots to flower, allowing time to cut through roots or spray. Once it blooms, the individual plant dies, but new ones grow from seeds found within 30 feet of the parent plant.

New York SWAT teams regularly visit about 1,000 sites, ranging from private residences to state roadsides. Workers wear waterproof clothing from head to toe.

Hogweed is one of the few invasive species that has such a severe human health impact people really need to know about it, said Chuck O'Neill, coordinator of the Cornell Cooperative Extension Invasive Species Program in Ithaca, N.Y. "Unfortunately, I'd say 80 percent or 90 percent of hikers have no idea what these plants look like."
In Washington, D.C., officials ask residents to help locate outbreaks. Vermont's state office of plant pathologist has found and destroyed hogweed in at least three counties.

Across Europe, eradications teams are using sheep and cattle, which are immune to the plant's poison, to help control the weed. Pigs, however, can't be used to battle the weed that gives them a bad name. They can suffer the same ill effects as humans.

The sap in giant hogweed is clear and watery, and contains toxins that cause photo-dermatitis, a skin reaction to ultraviolet rays. As a result, skin that comes in contact with the sap and exposed to sunlight blister and burn — injuries that can cause long-lasting skin discoloration and purplish scars. Sap in the eyes can cause blindness.

Hogweed's hollow stems are an unfortunate temptation for imaginative youngsters, too, who turn them into make-believe telescopes or peashooters, sometimes with horrendous results. Far worse than the usual rash caused by poison ivy or poison oak, hogweed exposure leaves the skin unable to protect itself from the sun.
The big difference is that poison ivy and poison oak are itchy and irritating, but hogweed causes a burn, said Kraus. Contact between skin and sap usually occurs when someone brushes against the bristles on the stem or breaks the stem or leaves.

If you come in contact with what looks like a giant hogweed plant, don't:

touch it.
use a weed-whacker or brush cutter because sap might splatter.
touch your eyes if your hands or arms come in contact with sap.

Do:

act fast. A toxic reaction can begin as soon as 15 minutes after contact.
quickly wash affected areas with soap and cold water, and get out of the sun.
apply sunscreen to the affected areas to prevent further reactions if you're stuck outside. Compresses soaked in an aluminum acetate mixture — available at pharmacies — can provide relief for skin irritations.
wash eyes if sap gets in them and wear sunglasses.
see a doctor if painful blisters form within 48 hours.

— Chasiti Kirkland