Poisonous to Touch Weed Series: Wild Parsnip (Pastinaca sativa)

Wild parsnip in flower growing amongst mixed vegetation near a pedestrian sidewalk. Photo by Kimberley Pacholko

Wild parsnip (Pastinaca sativa) aka poisonous parsnip is one of the phototoxic weeds we grow here in Canada. It is a non-native and as such is an aggressive and invasive species. It is the only one of the phototoxic weeds that has a yellow flower, the others bearing white umbels. It’s pinnately compound leaves are also quite different than the palmately compound leaves of cow parsnip and giant hogweed, both in form and size; wild parsnip leaves being somewhat smaller than cow parsnip and significantly smaller than giant hogweed. The overall plant height is also significantly shorter than both cow parsnip and giant hogweed. All differences aside all parts of this plant are phototoxic and can cause nasty burns that take weeks or months to heal and can leave scars. Wild parsnip burns are worse than cow parsnip but not as severe as giant hogweed.

Where Does Wild Parsnip Grow?

Wild parsnip is native to much of temperate Europe, eastern Europe, and western/central Asia (growing in Turkey, Iran, the Caucasus region, and the Western Himalayans). The plant was introduced to Canada, United States, South America and New Zealand. In the United States it has been found in every state except Alabama, Hawaii, Georgia, and Florida. In Canada it has been reported in every province except Nunavut. It has become increasingly common in eastern Ontario.

Habitats include disturbed areas such as abandoned yards, waste dumps, meadows, open fields, roadsides, railway embankments and fence rows. It can become a problem particularly in abandoned agricultural areas. It is often found in full sun, but can grow in semi-shade. It is tolerant of a variety of soils, but cannot survive in flooded environments.

Identification of Wild Parsnip

Overall growth habit: Wild parsnip will grow up to about 0.5-1.5m (2-5 ft.) tall, and it’ll look and smell much like a cultivated parsnip. The stem is hollow  (except at the nodes), with vertical grooves running its full length. The stem and its pinnately compound leaves with multi-toothed leaflets are a yellowish-green colour. The flowers are flat-topped umbels yellow in colour.

A wild parsnip plant in bloom growing singly. Photo by Kimberley Pacholko

Leaves: Seedlings have long, narrow cotyledons and a round-toothed first true leaf. Mature leaves are pinnately compound (leaves that have leaflets that grow across from each other along the stem) with 2-5 pairs of opposite leaflets and one diamond-shaped terminal leaflet. The leaflets are toothed and often shaped like a mitten. Leaves measure about 40 cm (16″) in length. The plant typically forms a spindly, low growing rosette of leaves in the first year.

First true leaves of a new wild parsnip seedling. Photo credit: Ohio State Weed Lab , The Ohio State University, Bugwood.org
A young wild parsnip plants. Wild parsnip leaf. Photo credit: Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
A young wild parsnip rosette. Photo credit: Theodore Webster, USDA Agricultural Research Service, Bugwood.org

Stem: light green about 2.5-5 cm (1-2 in) thick. It is smooth with few hair and deeply grooved.

Wild parsnip stems are light green and deeply grooved. Photo by Kimberley Pacholko

Flowers: Yellow umbels 10 to 20 cm (4-8″) across. They bloom from June through to October, in Canada (Invasive Species Centre n.d.).

Wild parsnip flower. Photo by Kimberley Pacholko

Roots: develop a thick funnel-shaped, edible taproot, which can grow to a depth of 1.5 m.

Seeds: the fruit are about 6 mm long and oval, each containing 2 seeds which mature in mid-summer. The seeds remain attached to the stem until they are dispersed by wind, carried on water, or spread through human activity. One plant produces, on average, 975 seeds with a median dispersal distance of 3 m. Seeds can remain viable in soil for up to 5 years (Invasive Species Centre n.d.).

Life Cycle: In the fall wild parsnip seed is dispersed, usually within 3m of the mother plant. In the spring eighty per cent of that seed will germinate within the first year; un-germinated seed can remain in the soil for up to 4-5 years but after the second season, the germination rate of any remaining seed falls off dramatically. These new seedlings will form a low, spindly rosette of leaves in the first year while the root is developing.

While this is occurring, plants from the previous season re-emerge from the soil and when the root and crown have reached a critical size, they send up a tall flower stalk toped with yellowish umbel flower heads (plants typically flower in their second year but it can take up to 5 years). Once they flower and set seed they die. Reproduction is solely by seed.

Wild Parsnip Look Alike Plants

  • Giant Hogweed, Heracleum mantegazzianum NOXIOUS WEED
  • Cow Parsnip (Heracleum maximum) NATIVE WEED
  • Poison Hemlock, (Conium maculatum) SECONDARY NOXIOUS WEED
  • Angelica Angelica atropurpurea NATIVE WEED
  • Queen-Anne’s Lace, Daucus carota NOXIOUS WEED

Symptoms of Wild Parsnip Reaction

All parts of the wild parsnip plant contain a phototoxic sap. When an individual gets the sap on their skin it causes a reaction called phytophotodermatitis. This is not an allergic reaction as with poison ivy rather it is a chemical reaction that occurs when the organic chemicals called furanocoumarins, contained in the sap, become activated by ultraviolet radiation. The activation of this chemical damages your DNA and changes the way your skin protects itself from ultraviolet (UV) light (Goldman R. Updated on Dec. 2018). This results in severe burns when exposed to the sun. This chemical reaction can happen as quickly as 15 minutes after getting the sap on your skin.

Symptoms may include:

  • intense local burning sensation
  • red rash
  • blistering
  • irregular patches on the skin
  • Discoloration and sensitivity to sunlight in the affected areas can remain for up to 2 years.

What To Do If You Come Into Contact With Wild Parsnip?

  1. Wash the affected area thoroughly with soap and COLD water as soon as possible.
  2. Keep exposed area away from sunlight for 48 hours.
  3. Immediately launder any clothing that has come into contact with wild parsnip.
  4. Wash down the surfaces of anything that has come in contact with the plant using gloves and protective clothing.
  5. If you are experiencing burns and blisters, you can try ice packs for pain relief or ibuprofen or acetaminophen.
  6. If needed, try an over-the-counter hydrocortisone cream to help soothe the inflammation.
  7. If the burns or blisters are severe or you see signs of infection, seek medical attention. They may recommend a systemic or more potent prescription topical steroid to help relieve your discomfort.
  8. If sap gets in your eyes, rinse them with cold water, wear sunglasses and seek medical help.
  9. If a reaction has occurred, the area of skin may be sensitive to sunlight for a few years. Keeping the area covered or wearing sunblock should help.

How To Get Rid of Wild Parsnip Plants?

You can hire a professional to remove the plants. If you decide to do it yourself be sure to wear the proper protective clothing; close-toed shoes or boots, long pants, long sleeved shirt, water proof gloves and ideally face and eye protection. Do not touch your face or any bare skin with your gloved hand. Also try not to touch the surface of anything other than the tools you are working with. When you have finished removing the wild parsnip wash your tools and any surface you may have touched. Wash your shoes and shoelaces off and change and wash your clothing.

The best way to control wild parsnip is by early detection and eradication. Watch for the short rosettes of leaves. If you only have a few plants on your property hand pull or dig them, or hoe them preferably early in the season. Black bag the plant debris. If you have small patches of them on your property dig out as much of the tap root as you can in spring while the soil is moist.

For larger properties, road sides and the such regularly mowing the area, especially when the flower buds are beginning to show (somewhere between the end of June and beginning of July) helps to keep them at bay and from flowering. It is not advisable to mow after this time as it leads to re-sprouting and spreading the seeds even farther with your mower. Black plastic can also be spread over these mowed areas to smother new growth. The plastic should be left in place for at least one season to ensure the roots are smothered. Visit Ontario’s invasive plants website for more details on how to manage larger outbreaks.

It is recommended that weed-whackers or trimmers NOT be used in the eradication of wild parsnip, as this spreads the toxic sap. Sap, although present all year, is most abundant during the summer when the plants are flowering, or have gone to seed.

Chemical Control:

Glyphosate, a systemic herbicide, is most effective when applied in the spring to the smaller plants, followed up by a summer application for missed plants or those that may have re-grown. Mulching the area 10-14 days after application will help to manage seedling germination.

Monitor the same location in following years (spring and summer). Seeds in the soil can be viable for up to 5 years, so continued vigilance in monitoring the area for newly germinating plants is important.

Good pre-emergent control for 2 to 3 years may be necessary for long-term control.

Summary

Wild parsnip has become a problematic weed here in southern Ontario and else where. Learning to identify it is key to both avoiding the painful burns caused by it and in eradicating it. Report sighting of this weed to the Invading Species Hotline at 1-800-563-7711 or visit http://www.invadingspecies.com or http://www.ontarioinvasiveplants.ca.

Poisonous to Touch Weeds Covered in This Series Include:

  1. Poison Ivy (Toxicodendron radicans and Toxicodendron Rydbergii)
  2. Giant Hogweed (Heracleum mantegazzianum)
  3. Cow Parsnip (Heracleum maximum)
  4. Wild Parsnip (Pastinaca sativa)
  5. Poison Sumac (Toxicodendron vernix)
  6. Poison Oak (Toxicodendron diversilobum) and (Toxicodendron pubescens)

Other Poisonous to Touch Plants Not Covered in This Series Include:

  1. Poke Weed (Phytolacca decandra): besides being mildly to highly toxic this plant can cause a rash in sensitive individuals.
  2. Stinging Nettle (Urtica dioica): the leaves and young stems of this herbaceous plant are fitted with stinging hairs tipped with formic acid and other irritants. If touched, these needle-like hairs inject the stinging acid into the skin, triggering a burning, tingling sensation and an itchy rash. Thankfully the symptoms usually do not persist longer than 24 hours.
  3. Monkshood (Aconitum napellus): This is a highly toxic plant. The neurotoxins, aconitine and mesaconitine can be absorbed through the skin and cause severe respiratory and cardiac problems. So do not pick or handle this plant without gloves, especially by the root.
  4. Oleander (Nerium oleander): This is a highly toxic plant. The gummy sap can cause skin irritation or possibly dermatitis in those who are sensitive. If you are growing this plant as an ornamental in your garden be sure to were gloves, long sleeves, long pants, closed shoes and protective eye wear before pruning this plant.
  5. Bloodroot (Sanguinaria canadensis): the flower of this plant produces a reddish toxic sap that looks very similar to blood and contains the toxin sanguinarine. If this sap comes in contact with bare skin it can cause burning. If you get a high concentration of sap on your skin it can even eat away the flesh. If ingested, it is deadly to animals.
  6. Wood Nettle (Laportea canadensis): like stinging nettle have stinging hairs along its stem.

Updated on July 1, 2021

References and Resources

Bayer Environmental Science Vegetative Management, n.d., Bayer Solutions: Wild Parsnip, Retrieved on Mar. 3, 2021 from: Bayer Solutions: Wild Parsnip

Frothingham S. 2019, Medically reviewed by Owen Kramer, M.D. Health Line, Wild Parsnip Burns: Symptoms, Treatment, and How to Avoid, Retrieved on Feb. 24, 2021 from: Wild Parsnip Burns: Symptoms, Treatment, and Prevention (healthline.com)

Goldman R. Updated on Dec. 2018, Medically reviewed by Shilpa Amin, M.D., CAQ, FAAFP , Health Line, Retrieved on Feb. 24, 2021 from: Hogweed Burns: How to Avoid Giant Hogweed and Treat Burns (healthline.com)

Invasive Species Centre n.d., Wild Parsnip, Retrieved on Mar. 3, 2021 from: Wild Parsnip – Profile and Resources | Invasive Species Centre

Schaefer K. 2007. PSEP Program Manager I. Iowa State University, Weed watch: Wild parsnip and poison hemlock, Retrieved on Mar.7, 2021 from: Weed watch: Wild parsnip and poison hemlock | Integrated Crop Management (iastate.edu)

Tassie, D. and Sherman, K. 2014, Invasive Wild Parsnip (Pastinaca sativa) Best Management
Practices in Ontario. Ontario Invasive Plant Council, Peterborough, ON., Retrieved on Mar. 3, 2021 from: OIPC_BMP_WildParsnip_Feb182014_FINAL2.pdf (ontarioinvasiveplants.ca)

The Ministry of Natural Resources and Forestry 2018 (rev. oct.2019), Wild Parsnip, Retrieved on Mar. 1, 2021 from: Wild parsnip | Ontario.ca

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