What NOT TO DO when you have wild parsnip

Wild parsnip disposal should be done very carefully - more details about what to do are listed below. However, there is a lot of misinformation on the Internet and the following is a list of disposal methods that should never be used:

1) Burn the plants

Some resources you find may advise that burning wild parsnip is a good control method. However, we recommend that you never burn this or any other poisonous plant. Inhaling the burning oils that will be in the smoke can be very dangerous to humans and animals that are in the vicinity or downwind of the burning.

2) Cut/dig up and throw away

To avoid further spread of the invasive plant, it's critical to thoroughly dry them out before moving them anywhere. Wild parsnip that has thoroughly dried out (left in black plastic bags in direct sunlight for a week or more) should not be dangerous to handle or move.

3) Compost

Composted wild parsnip plants can cause additional spread of the plant to new areas or new growth in areas where the plant was thought to be under control.

4) Allow livestock to eat the plants

Chemical compounds in the plant are known to reduce weight gain and fertility in livestock that eat it. Additionally, since animals can also experience burns from phytophotodermatitis, it's best to avoid any type of contact with wild parsnip.

5) Mow flowering plants

Once the yellow flowers are blooming, it is not advisable to mow as this promotes the spread of infestation. Mowing can be effective, but only during certain times in the plant's growth cycle. See more information below about the right times to mow.

What TO DO to remove and manage wild parsnip infestation

There are a number of methods that have proven effective to manage and prevent/stop spread of wild parsnip. The method that will be most effective depends on the time of year and the amount of plants involved with your infestation. (Please refer to this section regularly as it will be updated whenever we have new, credible information to add.) The following methods of management are all in accordance with the best management practices established by the Province of Ontario's Invasive Species Centre and Ontario Invasive Plant Council [PDF].

Regardless of which method you choose to manage a wild parsnip infestation, it is essential to follow-up with site monitoring to check for re-sprouts and missed plants.

MOWING

Mowing small infestations can be a cost-effective and efficient way to manage and control wild parsnip.

It's important to mow at the correct time to prevent increasing the spread of infestation. Mowing should occur as soon as the flower stalks appear, but before the plant flowers. This generally occurs in May/June, though flowers do start to appear in June. Mowing in July or August will spread the seeds and increase infestation. Mowing too early is also problematic as it can cause the plant to double or triple, increasing the likelihood of spread once it starts to flower.

Mowing is a long-term elimination solution. It has to be repeated at the right time for several years to reduce and eventually eliminate infestation. The person(s) doing the mowing should use care to wear proper safety gear for handling wild parsnip (described above). Additionally, any equipment that comes into contact with the plant and its oils should be thoroughly cleaned to prevent the oil from getting on to people or animals and to prevent unintentional spread from seeds that may be in the equipment from early flowering plants. The mowed stems should be avoided to prevent phytophotodermatitis burns to people or animals that may be in contact with the cut plants. The cut plants should be thoroughly dried before disposing of them (do not burn or compost).

PULLING / DIGGING

This method is most effective right after a rain when the ground is soft or when the ground is completely dried out due to drought. This causes the taproot to shrink making it easier to release it from the ground. A variation of this method is severing the taproot before the plant goes to seed. The taproot can be severed about 2.5 to 5cm below the soil. Spring is the best time to sever the taproot - while it is still a manageable size.

TARPING

Tarping is best used with other control methods - mowing or digging - and it's a season-long process that should be quite effective.  After mowing or digging, cover the area with black plastic. This will smother any new plant growth. The plastic must be left in place for one full growing season as new plants can come up into July and August. When the plastic is removed, you can replant and restore the area.

CHEMICAL CONTROLS

The Pest Management Regulatory Agency site has an up-to-date listing of all herbicides that are designated for controlling wild parsnip. Additionally, Publication 75 (Guide to Weed Control) from the Ontario Ministry of Agriculture, Food and Rural Affairs gives specific information about chemical control of wild parsnip:

Wild Parsnip - Publication 75, Guide to Weed Control 2014-2015

Pesticide use is regulated through the Ontario Pesticides Act and Ontario Regulation 63/09. If you use pesticides, you are responsible for complying with all federal and provincial legislation. You can contact the Ontario Ministry of the Environment for additional information.

The most effective time to apply herbicide is in the early spring once the flower stalks have grown. Avoid treating with herbicides once the plant is in full flower as this does not prevent the setting of the seeds.

Residents who have infestation on private property can arrange for commercial pesticide treatment. Do your research carefully to pick the right service provider - one that knows how to effectively treat wild parsnip.

What control method should you use?

Disposal

The Province of Ontario's wild parsnip information pamphlet [PDF] states this about disposal:

Once you have removed Wild Parsnip plants from the ground, DO NOT burn or compost. If possible, leave the stems at the removal site allowing them to completely dry out [Note: this can be facilitated by tarping if the area is smaller]. Taking safety precautions while handling the plant, place in black plastic bags and leave in direct sun for at least a week. Contact your municipality to check if these bagged plants may then be sent to your local landfill site.

We have confirmed with City of Ottawa Waste Processing & Disposal staff that Ottawa residents can leave bagged wild parsnip out for collection. Here are the guidelines:

1. Plants must be in black garbage bags.
2. The plants must not be left for collection until they've been in the bags in direct sunlight for at least 7 days. (This will prevent workers from coming into contact with the oil and getting burns.)
3. Wild parsnip is not allowed in the green bin.