Speaking of Nature: Beware of the wild parsnip

  • A hover fly visits the extremely small flowers of the wild parsnip. Inset: The distinctive seed pods are actually much larger than the flowers. For The Recorder/Bill Danielson

  • The wild parsnip can grow 5 to 6 feet tall and is easily recognizable once you know what you’re looking for. Inset: Note the vertical ridges on the stem. For The Recorder/Bill Danielson

  • Bill Danielson

For The Recorder
Sunday, July 16, 2017

There are certain books in my library that are very special to me. All of them are full of invaluable information about the natural world, but a few of them are — I don’t know — special. One such book is my “Newcomb’s Wildflower Guide.”

This book has helped to open my eyes to the world of wildflowers in the northeastern United States, and although I have added larger, more detailed books to my library over the years, I still rely on Newcomb’s for my initial identifications. The book’s secret is the special key to identifying plants with flowers.

First, you classify the number of regular parts in the flower. Then, you identify the positioning of the leaves. Finally, you identify the type of leaf.

Using this method, I set about the process of identifying a tall yellow “weed” that had suddenly sprung up by the corner of my driveway. I’ve seen this plant in the past, and I’ve even taken some wonderful photos of insects that visit its flowers, but for some reason I’ve neglected to identify it.

So, I will remedy that situation. I see that the extremely tiny yellow flowers have five petals (Category 5), the leaves are alternate along the main stem (Category 3) and the leaves are deeply divided (Category 4).

The code 5-3-4 takes me to a section of the dichotomous key that starts with “leaves divided.” So far, so good. The next step is a description of the flower arrangement. The first choice is “flowers in dense spikes, racemes or heads.” Negative. My plant has flowers that are in a broad, flat arrangement called an “umbel.” Low and behold, that’s the next choice!

The final choice is about flower color. The first choice is “white, pink or greenish flowers.” Negative. The other choice is “yellow or purple flowers.” Jackpot!

I am directed to Page 226 of the book, and I instantly find the plant I am looking for. Most of the 1,375 plants covered by the book are presented in beautiful black-and-white line drawings that are of such quality that they are sufficient for identification. It appears that I’m looking at a wild parsnip (Pastinaca sativa). The plant can grow up to 5 to 6 feet tall, which is dead on. The clincher is the drawing that shows vertical ridges along the stem that remind me of stalks of celery.

I go online to see if I can find a “second opinion.” I instantly hit pay dirt with several different websites that warn of the hazards of wild parsnips. Each website has color photos that match my home specimen perfectly, and they warn of this plant’s dangerous toxicity.

It seems that the sap of the wild parsnip is filled with chemicals known as “furanocoumarins.” When these chemicals are exposed to ultraviolet light, they can cause a condition known as “phytophotodermatitis.”

The symptoms — from personal experience — are terrible. First, you develop a blistering chemical burn that itches like poison ivy. The blisters are painful and darken when exposed to sunlight. Worst of all, the affected skin will remain sensitive to light for years.

This solves a personal mystery for me. Every spring, liberated by warm weather, I shed my long clothing for shorts and sandals — and, every spring, my lower legs develop “poison ivy,” despite the fact that I haven’t been out in the woods for months. I suspect the wild parsnip is the guilty party. Catch one of these plants with a mower and you will release a toxic aerosol cloud of parsnip sap. I’ve probably done this to myself every year without even knowing it.

So beware of the wild parsnip! It’s a beautiful plant, but it is also extremely hazardous to humans. Once you know what you’re looking for, you will see it growing along roadsides almost everywhere you go. If you find this plant growing in your yard, you will want to be very careful when removing it. Wear gloves and long sleeves and wash with soap when you’re done.

Also, remember that this plant has a long, white tuber (like a white carrot) that needs to be removed or cut with a shovel to prevent regrowth. Now that I’ve identified and photographed the plant, I am going to take my garden spade and remove every plant I find. I’d like to go just one summer without being the object of a chemical warfare attack.

Bill Danielson has worked for the National Park Service, the US Forest Service, and the Massachusetts State Parks. He has been a professional writer and nature photographer for 19 years and he also teaches high school biology and physics. Visit www.speakingofnature.com for more information, or go to Speaking of Nature on Facebook.