Tuesday, July 10, 2018

Beware the Giant Hogweed and other summer hazards -- 5 July 2018 column


Nearly every summer, fun in the sun comes with warnings.

A few years ago, red imported fire ants marched into the Southeast and ruined forever the pleasure of walking barefoot in the grass. Lately, ticks and the diseases they spread have become a real and present danger not only in the woods but also in backyards.

Last month came news the giant hogweed has been found in Virginia. The what?

I’d never heard of it, but this is a plant only a demented Mother Nature could love.

Encountering giant hogweed, Heracleum mantegazzianum, you might think Queen Anne’s lace on steroids, but Queen Anne’s lace is a delicate wildflower -- or a pesky weed, depending on your point of view and where it grows. In either case, it’s harmless.

Giant hogweed is anything but. As the name suggests, it’s huge -- towering 8 to 14 feet tall -- with small white flowers that cluster into a flat-topped “umbrella” up to 2 to 5 feet across.

Like many pretty things, though, it needs to be admired from afar.

The troublemaker is its watery, clear sap. It contains chemicals called furanocoumarins, which cause human skin to be highly sensitive to ultraviolet light. Exposure to the sap and sunlight can result in the painful blisters of third-degree burns, scarring and even blindness.

Sensitivity can last years, meaning people must continue protecting their skin from sunlight or risk burn flare-ups.

If you happen to brush up against giant hogweed and it touches your skin, wash the area thoroughly with soap and water and stay out of the sun for 48 hours, experts say.

Giant hogweed had been found in a dozen states from Florida to New England to the Northwest. Then, last month Virginia Tech plant experts confirmed 30 plants in Clarke County, near Winchester, and subsequently confirmed plants in Rockingham and Fauquier counties and Alexandria.

These were intentionally planted as ornamentals decades ago, and the good news is they hadn’t spread. That’s lucky since a single plant can produce upwards of 20,000 seeds a year, giving it the potential to spread very quickly.

Giant hogweed is a toxic, non-native invasive classified as a noxious weed, which means it’s against the law to propagate, sell or transport it – not that you’d want to.
Native to the Caucasus region between the Black and Caspian Seas, it has little, if anything, to commend it.

It has long bedeviled Britain, where it was imported in the 19th century and widely planted in gardens as an impressive ornamental. Dubbed “Britain’s most dangerous plant,” it spread throughout the country, along streams and river banks, in parks and residential areas, where it crowds out other plants leading to soil erosion. Some children have used its hollow stems, which are two to four inches in diameter, as pea shooters with dreadful consequences.

Gardeners here imported it from Britain about a hundred years ago as an accent plant.

If you think you spot giant hogweed, take photos and compare them with those online. Then, contact a Virginia Cooperative Extension agent or the Virginia Department of Agriculture and Consumer Services. Never mow it or use a weed whacker, as that would release the sap into the air.

Virginia Tech’s site is an excellent resource as is the Virginia Master Naturalists’ “Socrates Project” publication on poisonous plants. Naturalists named it to remind readers of the ancient Greek philosopher who died in 399 BC “after drinking an extract from poison hemlock, a plant widely found in Virginia today.”

Chances are good what you suspect is giant hogweed is something else – like cow parsnip. The Virginia native grows throughout the state and looks very similar, if shorter.

It and two other giant hogweed look-alikes -- angelica and wild parsnip -- can also cause mild rashes or burns, but they’re not nearly as dangerous as giant hogweed.

But it’s summer and time to get outdoors and enjoy it while we can.

Just as we survived the fire ant scare, so too can we deal with the evil giant hogweed.
Be careful out there. Don’t let a plant rob you of your summer fun.

©2018 Marsha Mercer. All rights reserved.

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