Plant Description and Life Cycle
Parsnip is a biennial root vegetable of the Apiaceae family (formerly called Umbelliferae). In its first year, a cluster of leaves grows from a basal rosette and reaches up to 40 cm (16 inches) in height. A large taproot develops to store nutrients for the second year’s flowering stage. The leaves are broad, with opposite leaflets having toothed edges. They are somewhat similar to celery leaves. In its second year, a large stalk, which is grooved and hollow, grows 160 cm (50 inches) or more tall, and produces flowers.
The yellow flowers are small and grouped in umbels, which are round flat-topped arrangements similar to upside down umbrellas. Each plant produces many flower umbels, and therefore many seeds, which are flat and oval. Once the plant has flowered and gone to seed, it dies. The seeds stay viable in the soil for two years or more before emerging as new plants.
Parsnip grows well in disturbed soil particularly in sunny locations. It easily establishes itself along roadsides, railway tracks, and agricultural fields. It is very seldom found in forested areas.
This plant is believed to have become naturalized from cultivated crops that were brought over from Europe. In the 1740’s, it was observed to be growing wild in abundance around Montreal and Quebec City. By the 1880’s, it had become common along roadsides and orchards from Manitoba to New Brunswick and in British Columbia. By 1950, wild parsnip was found in every province and the Yukon. Today it is found across most of North America.
While the root of parsnip is safe to eat, the plant contains chemical compounds, called furanocoumarins, which can cause a condition called phytophotodermatitis. This literally translates as ‘plant-light-skin inflammation,’ and is commonly called parsnip burn.
Furanocoumarins occur in the sap or juices of certain plants, including celery, limes and parsnip. When parsnip sap on the skin is exposed to sunlight, a chemical reaction can cause what looks like a rash or burn. The severity of this skin condition depends on the quantity of sap and the amount of time the skin is exposed to sunlight or other sources of UVA ultraviolet light. It may cause a slight reddening of the skin, or create a rash-like effect with some sensitivity or itching. In more serious cases, a burning pain can be felt and blisters can erupt within 24 hours. Heat and moisture may worsen the effect. A sensitivity to sunlight and a darkening of the skin called hyperpigmentation may be present afterwards, but this will gradually fade over a period of weeks or months. In severe cases, it may take years for the discolouration to fade.
While contact with the eyes may cause conjunctivitis, there are no records nor research supporting the possibility of permanent blindness.
The easiest way to avoid any chance of parsnip burns is to learn to recognize the plant and avoid it, particularly when it is in its flowering stages. Wear gloves, long sleeves, pants and high boots if working among or removing parsnip plants, and use protective eyewear if mowing or weed whacking.
If you do get sap directly on your skin while you are in the sun, wash the area right away with soap and cold water and stay out of the sun or a tanning booth for the next 48 hours. If you go out into the sun within the two days after exposure, cover yourself well with sunscreen and clothing.
Parsnip propagates by seed only, so the primary focus to contain its spread is to prevent seeds from forming and germinating. This can best be achieved by removing or killing plants, or by preventing them from flowering and going to seed. These goals are achieved in various ways, depending on
location, number of plants present, and whether physical, mechanical or chemical methods are used.
It is important to avoid getting parsnip sap on exposed skin when working with these plants and to wash off any sap before the sun causes it to react and blister. Therefore it is advisable to wear protective clothing, footwear and eyewear. Clothing and equipment should be washed thoroughly afterwards, as well as any areas of the skin that may have touched the sap.
Cutting and Snipping
Parsnip plants may be cut off at the base at any time. However, the cut must be below ground level. If the cut is not deep enough into the taproot, first year and early second year plants may grow back. Flower stalks may be cut and removed from second year plants, but newer flower stalks may sprout so cutting may
have to be repeated. This is best done when the flowers are close to or in seed, around the fourth week of development. Flowering and seed formation usually occurs from mid-June through to September or October. The flower clusters can be snipped using a small clipper or scissors. These flowers must be disposed of in a sealed garbage bag, or well-buried to ensure no further seed development.
Parsnip plants that are pulled or dug out cannot regenerate. Plants may be dug up at any time with a shovel or spading fork, or pulled out by hand. Pulling plants is easiest early in the year or after a rain when the ground is moist, or during a drought when the taproot shrinks. Another opportune time for pulling is in the second year when flowers have started to develop and the long taproot has shrunk to support that growth. Some plants may need loosening with a shovel or spading fork before pulling. The roots can be quite long, but if most of the root is removed, the remaining portion of the root will not likely regenerate.
Areas with widespread growth of parsnip, such as along fence lines, roadsides and empty lots, may be mowed, but timing is important and mowing will need to be repeated. The two-year-old plants flower
between June and October and they can put up new, shorter flower stalks if the main stalk is removed. These shorter stalks may be lower than the mower blades. Mowing must be done before the
flowers go to seed. Several mows may be required to reduce plant growth and prevent reseeding.
Tarping and Mulching
For localized patches of parsnip, tarps or mulch may be used to cover the area and prevent growth. This is best done after as many plants as possible have manually been removed. The preferred time for tarping is in late autumn or early spring. Tarps or mulch should be in place for a full growing season.
Planting Naturalized Species
To prevent parsnip from spreading or establishing itself in a disturbed area, put in native species either as plants or seeds. Fast-growing taller plants are ideal, such as goldenrod, milkweed, and asters. This is especially helpful for places that are newly disturbed.
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Friends of Lanark County is not responsible for, and expressly disclaims all liability for, damages of any kind arising out of use, reference to, or reliance on any information contained in this flyer.
I’ve never paid it much heed, frankly. The real one that people are more justified to be concerned about is the giant hogweed.
— Holly Bickerton, Ottawa environmental consultant
“I have never heard of a furanocoumarin burn from second-hand exposure by pet fur, like we hear about in poison ivy all the time. First of all, it takes a demonstrable quantity of sap to cause this burn; the phenolic urushiol in Toxicodendron spp. can initiate a reaction from an almost invisible quantity. But if the question is worded, “…after roaming in the wild parsnip,” the answer is almost certainly NO. Remembering that injury is a prerequisite for sap release in Pastinaca sativa, there is no scenario I know for a dog or cat injuring the cuticles of enough plants to get a sap coverage like this would take (I have never seen such a case, and the rare mention in the literature is usually without reference source), although I admit, not theoretically impossible”.
Peter Carrington, Ph.D.
Assistant Curator, Collection Manager
Michigan State University
What the experts say:
“….with minimal caution and basic first aid, these plants are of minimal danger, especially compared to the danger; medically of being exposed to most of the powerful herbicides available for temporary control since as an established weed, the seed bank for this species (wild parsnip) is much more extensive than anyone could afford to spray; and ecologically of having portions of your ecology devastated by the indiscriminating power of a broadleaf herbicide”. Dr. Carrington PHD
“Parsnip is a biennial, so it will die after it sets seed in its second summer. The trick is to mow before seed set, which will prevent a new crop of seeds from making the infestation worse. The one-year-old plants will be back next year and will be ready to reproduce, so you’ll need to mow again. Seeds in the soil may produce new seedlings for a few years, but every year you should have fewer and fewer plants if you mow repeatedly.
Just be sure to wear long pants and long sleeves so as not to get the sap on your skin. Some people are more sensitive than others and can get a rash. I find parsnip to be over-rated in terms of how dangerous it is though. Poison ivy is much worse for those who are allergic! For some reason, there was quite a bit of panic last year about a plant we have been living with for 100+ years.” – Naomi Cappuccino, Associate Professor, Department of Biology