Wild parsnip, also known as poison parsnip, is native to Europe and Asia. It has been grown in North America since at least 1609 (Virginia). The plant’s root resembles the domestic parsnip and is also edible. It’s likely that it was brought to North America by European settlers as a food source.
A biennial, meaning the plant only lives for two years and then dies
First year plants form low-growing leafy rosettes
In it’s second year the plant produces a flowering stalk
Flowering portion is umbrella shaped (like Queen Anne’s Lace) with small, yellow, 5-petaled flowers
Second year plants grow 50-150 cm in height
Leaves consist of 2-5 pairs of leaflets that grow opposite each other along the stem. They tend to be mitten-shaped, with serrated edges.
Terminal leaf is diamond-shaped
The stem is green and smooth, 2.5-5 cm thick, with few hairs
Spreads easily by seed by wind, water, attaching to clothing/equipment
What it does in the ecosystem
Wild parsnip is an aggressive invasive plant that is mainly found in disturbed areas.
Wild parsnip outcompetes native plants and reduces local biodiversity
Where it invades, it tends to produce dense stands that quickly become monocultures.
The plant reproduces mainly by seed, but some sources suggest that vegetative growth is also possible by rhizomes.
The plant seeds prolifically, producing an average of 975 seeds per plant in its second year of growth.
Wild parsnip, like its relative giant hogweed, contains toxic sap.
This sap contains a compound (furanocoumarin) that reacts with skin and sunlight to create a sunburn.
The burn can blister and scar, and the affected skin may remain sensitive to sunlight for as long as two years.
Care should be taken when handling wild parsnip. Protective clothing is required to protect yourself from the toxic sap.
If sap comes in contact with the skin, wash the area immediately and avoid direct sunlight.
These burns are also seen frequently on livestock legs and faces, especially after mowing.
The plant is also unpalatable for livestock, and as such can reduce the grazing capacity of pastureland.
Compounds found within the plant can affect livestock health, reducing both weight and fertility.
Wild parsnip infestations in fields can reduce the quality or salability of crops, especially hay, oats, and alfalfa.
Before selecting a control method, consider the size of the infestation, your available resources, and the amount of effort you are willing to expend.
Often, multiple control methods are used simultaneously to increase their efficacy.
Consider the local ecosystem and what other organisms or ecological processes may be affected by management.
Ensure that you have properly identified wild parsnip, as there are many plants belonging to this family with similarly shaped flowerheads, both native and invasive.
Native lookalikes include cow parsnip, seaside angelica, and purple-stemmed angelica.
Invasive lookalikes include Queen Anne’s lace, giant hogweed, and woodland angelica.
Similar to garlic mustard, wild parsnip spends its first year of life as a rosette: a low-growing arrangement of leaves that does not flower or produce seeds.
It is important not to miss these rosettes when managing the wild parsnip, as they will grow into mature, seed-producing plants the following year.
Due to the phototoxic sap in wild parsnip, it is recommended that you take precautions to protect yourself against burns.
Protective clothing should be worn, including a non-absorbent coverall (Tyvek) or another non-absorbent outer layer, waterproof gloves, eye protection or face shield, long pants and shirt, and rubber boots.
You may also want to tape your sleeves to your gloves to ensure they do not ride up and expose skin during management.
If exposed to sap, keep the area out of sunlight, wash the area with soap, and flush with cold water.
Avoid exposing that area to sunlight for several days after.
Management should always be done before seeds begin to form. Disturbance of plants that are in seed will cause further spread.
Physical removal of wild parsnip by digging is recommended, especially for smaller populations.
It is key to try to remove the entire taproot, as this will likely regrow if left in the soil.
Removal should take place early in spring as the soil is moist making it more likely to be able to remove most of the tap root.
Dig the plant up using a shovel or spade, taking care not to break the plant as this will release the toxic sap. Monitoring the site for regrowth is important as some of the tap root may have been left in the ground.
Mowing just after peak blooming but before seed set has proven effective in controlling outbreaks of wild parsnip.
Seeds are normally produced in late summer-early fall, varying between populations.
By mowing at this time, most of the plant’s energy will be put into aboveground parts meaning roots will be at their weakest.
Weak roots mean that regrowth should be limited.
As the plants are guaranteed to grow back after mowing, repeat the treatment every few weeks.
SEED HEAD CLIPPING
If managing the plant after it has gone to seed, it is important to first clip and bag all seed heads to prevent the seeds from being dispersed during managment.
Carefully place a plastic bag over the seed head.
Cinch the bag around the stem.
Clip the stem below the bag.
This will ensure that the entire seed head has been deposited into the bag, with little chance for accidental dispersal.
If used alone, this will reduce the reproductive expansion of the population but not offer the possibility of eradication.
The plant dies after producing seed, so over time, this practice may cause the population to shrink.
After physical removal, covering the area with a thick tarp can increase the efficacy of removal efforts. Covered plants will overheat and gradually die off due to a lack of sunlight (no ability to photosynthesize and make food) under the tarp. When selecting a tarp, the darker the colour and the thicker the material the better.
Pulling wild parsnip is not considered to be an effective management method.
Digging and/or mowing should be undertaken instead, as these methods are more effective and less labour-intensive.
Burning is not a recommended method of control as it is not effective alone.
Burning may also aerosolize toxins from the plants’ sap causing possible health risks to those that inhale them.
Chemical control methods exist, but the PEIISC does not offer advice on chemical control measures at this time.
If using chemical controls, it is imperative that all local legislation and manufacturer’s instructions be followed during application.
FOLLOW-UP AND DISPOSAL
As is the case with most invasive plants, return visits to the site after management and in subsequent growing seasons will be required to completely eradicate wild parsnip.
Repeat management as regrowth appears for several years after initial removal efforts or for as long as regrowth is seen.
This is because the plant may regrow from leftover root fragments and seeds, which can remain dormant in the soil for several years.
Each time you manage the site, collect, bag, mark, and dispose of all plant parts properly.
Bag the plant material in clear plastic bags.
Mark the bags boldly with a permanent marker. Write “INVASIVE PLANT” or “WILD PARSNIP” on the bags.
If you have a place away from foot and wildlife traffic, you can dry out the material, making it much easier to move.
Leave the bags open and in the sun for a week to dry.
Only do this if you can guarantee that the plant will not be spread from where it is drying
Double bag the bags to prevent accidental dispersal later on and protect waste handlers from the plant’s toxic properties.
Tie the bags tightly and place them in your usual residential waste collection (THE BLACK BIN)
Never place invasive plants into the compost. This may allow them to become established once they reach the heap.
Clean and remove all plant parts from any equipment, clothing, or vehicles before leaving the site to prevent spread.
Hose off gear and wash with soapy water.
Care must be taken when cleaning equipment contaminated with toxic sap to prevent skin exposure.
Remove clothing carefully to avoid touching contaminated parts.