Poisonous Plants

Wild parsnips a health menace along local roadsides

By Rob Mooy Kingston This Week

There is a new danger lurking along our roadsides, fields and trails when you head out for a walk in the wild this summer. What looks like a colourful wildflower is actually a toxic plant that could burn your skin and hurt your eyes.

Along with poison ivy, there is now a second plant to avoid. Wild parsnip an eye-catching colourful non-native weed has made it’s way to North America from Europe and Asia.  It grows in large patches or as scattered plants along roadsides, public recreation areas, around sports fields, pastures, fence rows and in disturbed open areas. It can grow as tall as two metres.

The weed resembles Queen Anne’s Lace (also known as wild carrot), a noxious weed common to Canada and recognizable by its white flowers.  “Wild parsnips, which have a yellow flower, contain a chemical compound that can cause severe burn blisters when activated by sunlight,” explains Chris Hargreaves of the Friends of Lemoine Point.

Wild parsnip causes phyto-photodermatitis, which happens when the sap of the plant, from broken stems and leaves, touches the skin and is exposed to ultraviolet light (whether cloudy or sunny), says Hargreaves. Within 24 to 48 hours, the affected area will first redden and in most cases be followed by blisters that can be painful for a couple of days. In many cases, the blisters will lead to brownish pigmentation that can last for years.

Unlike poison ivy, the reaction caused by contact with wild parsnip sap is not an allergic reaction. Toxin in the sap is absorbed by the skin and energized by ultraviolet light. Moisture from perspiration speeds absorption. Burning is inevitable if skin comes in contact with juice from cut or broken stalks, leaves or flowers. The juices are most potent while in flower. No one is exempt. Symptoms usually take 24-48 hours to develop, but could take longer. Mild exposure is similar to sunburn. Severe exposure causes skin to blister.

People who come in contact with the toxic liquid are advised to quickly seek shelter to stop the sap from photosynthesizing, and to wash exposed skin thoroughly with soap and water. Skin can turn red one day after exposure. Inflammation may also occur after three days. Those who have a reaction are advised to seek medical attention.

If the sap gets into the eyes, it may even cause temporary or permanent blindness.

“It seems to me that wild parsnip has been around for years, but in small quantities, says Hargreaves. “In 2009 there was a lot more of it seen around eastern Ontario. This is generally attributed to last year’s cool, wet summer.”  Wild parsnip is usually a biennial, with a two-year growth cycle.  “Last year’s wet weather produced an abundance of plants that came from rosettes which grew in 2008. It also caused a lot more seeds to grow into rosettes, and these rosettes have produced the very large number of mature wild parsnip plants being seen this year,” explains Hargreaves.

His advice to anyone who sees these plants is to stay clear.  “If you are likely to be in contact with wild parsnip, cover up,” he says.

Once exposed to the sap there are a couple of things that can be done.

• When the toxin is absorbed into the skin and is exposed to sunlight, some reaction is inevitable. Immediately cover exposed skin until it can be washed with soap and water.
• To relieve symptoms – cover affected area with a cool, wet cloth. If blisters appear, try not to rupture blisters as long as possible, to avoid infection, keep area clean and apply antiseptic cream.

It’s not as big a problem for pets, but this plant can still hurt them.

“The plant has a chemical in the leaves that is secreted in the plant oil which could find it’s way on pets feet if they walk through the plants, or likely on a cat’s tongue after grooming,” explains Dr. Jeff Latimer of Princess Animal Hospital. “Because most dogs and cats are not attracted to the plant, I feel that seeing these lesions are unlikely as the pet would have to find the plant, walk through it, then get enough sun light to cause the reaction.”  “This weed is a larger issue in sheep, cows and horses who may eat the plant…. which can be fatal. There are varying degrees of toxicity depending on the individual animal, and the amount ingested.”  Once you have learned to recognize the plant, you quickly notice just how abundant this plant is. It’s everywhere.

How do we control them and get rid of them?

“If one just thinks of quantity, trying to get rid of wild parsnip will be like trying to get rid of dandelions,” says Hargreaves. “But wild parsnip is toxic, so trying to get rid of it is much more complicated than dealing with dandelions.”  The simplest method of control may be to regularly cut the grass/plants/weeds in green areas alongside roads, and in areas the public uses. This may prevent the spread of wild parsnip into new areas.  “It’s everywhere,” agrees Karla Maki-Esdon, communications co-ordinator with the Cataraqui Region Conservation Authority. “It’s particularly prolific along the 401 this year, especially through the construction zone. It may be that it’s more noticeable because those areas haven’t been mowed.”

The best way to control wild parsnip is by early detection and eradication.

“If you only have a few of them in your yard, you can remove them by digging or hand pulling (especially after all the rain we have had lately),” she says. “Be sure to wear shoes or boots, long pants, long sleeves, gloves and goggles when you are working near it. Dispose of the plants in the garbage. To do otherwise will spread them further.”  For large infestations, mowing at the right time of the year can help to control them. That is when the flower buds are beginning to show, so it’s probably too late now. Mowing later in the season will help to spread the seeds.

The best way to control the spread of wild parsnip and keep it at bay is to mow or “weed eat” it just when the flower buds are beginning to show (somewhere between end of June and beginning of July). It’s crucial to remember that cutting the plant down with a mower or trimmer later in the season is not a good idea because mowing leads to re-sprouts and weed whacking spreads the toxic sap.  Hargreaves is quick to add that whatever method you use to remove wild parsnip it is necessary to wear protective clothing.  More information to assist in identifying wild parsnip can be found on the online weed identification service at  www.weedinfo.ca.

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