Giant Hogweed

Giant hogweed


There are a number of plants that look very similar to Giant hogweed such as Cow parsnip, Purplestem angelica, Woodland angelica, Valerian, Lovage, and Queen Anne's-Lace (also known as Wild carrot). However, these plants are not as large as a mature Giant hogweed, which grows up to 5.5 metres tall under ideal conditions. The white flower clusters resemble those of Queen Anne'sLace, but tend to be more widely spaced and can form a flower-head almost one metre wide. Hogweed stalk - Note course hairs



Note jagged edges of mature leaves





  The Dangers: (Source: U.S. Dept. of Agriculture)
Giant hogweed can cause a significant reaction if sap from a broken stem or crushed leaf, root, flower, or seed comes into contact with moist skin (perspiration will suffice). Irritation is NOT immediate.

Within 24 hours, burn-like lesions form, followed by large, fluid-filled blisters within 48 hours. On rare occasions, the burns and lesions may require hospitalization for treatment. Even minute amounts of sap in the eyes can cause temporary or permanent blindness.

The Antidote:
Immediately wash skin thoroughly with soap and water, removing the sap and hopefully preventing any reaction with subsequent exposure to sunlight. Treatment with prescription topical steroids early on may reduce the reaction.



Right: Young hogweed seedling



Mechanical control:
Spring Removal (i.e. early May): Use a spade to remove as much of the root as possible. Digging up older plants can be difficult since roots can grow deeper than one metre. The plant might re-grow from the root and you may need to dig repeatedly to remove it completely. Or, you can cover the dug area with black plastic to smother out new growth. If it's possible to use machinery, mow new growth every two weeks.

Summer Removal (i.e. early July):

Control Using Herbicides:


In the event of any direct exposure/contact to this plant If you get sap on your skin wash the area well with soap and water. Keep the affected area out of the sun. If photo dermatitis (inflammation of the skin caused by exposure to sunlight) occurs, see a doctor. If you get sap in your eye, flush your eye with water immediately and see a doctor immediately.



Patch of phragmites

This plant destroys wetlands!

Phragmites (frag-my-tees) is an invasive perennial grass that has caused severe damage to wetlands and beaches in Ontario for several decades. In 2005, it was identified as the nation's "worst" invasive plant species by researchers at Agriculture and Agri-food Canada. Despite this designation, invasive Phragmites is still sold as an ornamental plant in some garden centres. There's a large area of phragmites on the side of Forty Hills Road, near the north end of it.

We do have native phragmites that are much smaller and that do not threaten the plants or wildlife nearby. Invasive Phragmites has an intricate system of specialized roots that secrete toxins into the soil to impede the growth of and kill neighbouring plants. Native & invasive phragmites

Stands of invasive Phragmites reproduce primarily through the extension of runners or through the dispersal of root fragments that readily grow into new plants. Root fragments can be transported by flowing water or winds or moved around by animals. Human actions, such as the horticultural and agricultural trades or the movement of boats, trailers, and ATVs, can also disperse root fragments. Once it is established, a new invasive Phragmites plant can grow several metres in height and produce up to 2000 seeds every year.

The Dangers:

Dealing With It

Phragmites is a serious problem. It grows so dense that wildlife cannot get through it. And when it's disturbed, it flourishes by dispersing root fragments onto any human or animal who struggles through it. Professional removal is usually required, according to the MNR. Nevertheless, here's some pointers from their web site:


If you discover some phragmites, please report it to the Invasive Species Hotline at 1-800-563-7711.