Fri. Feb 23rd, 2024
Arrowhead staff say "hold the mustard!"

Garlic mustard may seem like a gourmet condiment, but it is actually an invasive species in North America, introduced from Europe more than 100 years ago.

It is a major enemy in the ongoing battle to maintain biodiversity in Arrowhead Provincial Park and many other provincial parks. It is considered one of the largest forest trespassers in Ontario.

The threat posed by garlic mustard

Garlic mustard can survive in a wide range of habitats and spreads very quickly. A single plant can produce 150 pods with up to 22 seeds per pod. That means a single plant can produce over 3,000 seeds!

Displaces native wildflowers (such as White Trillium and Canada Mayflower) as well as young trees.

White trilliums.

Without intervention, a healthy and diverse understory can experience a rapid decline in biodiversity as Garlic Mustard outcompetes its neighboring native species.

Invasive species can drastically alter the forest floor by limiting the amount of light and moisture in that habitat, as well as changing the type of plant debris that falls on it.

Salamanders, like this blue-spotted salamander (found in the park by our team removing garlic mustard) live on the forest floor, often hidden under rocks and logs, and feed on invertebrates.

Small black salamander with blue spots.

Natural habitat is much better for native wildlife than habitat dominated by invasive plants.

The battle continues at Arrowhead

Garlic mustard was first identified and eliminated by an Arrowhead Park naturalist 13 years ago, in 2005.

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In 2009, the park began a more vigilant annual mapping, reporting and removal process, to prevent further spread of the plant in the park.

Hand holding heart shaped lobe leavesGarlic Mustard in its first year of growth. Garlic Mustard is biennial with stem flowering occurring in its second year of growth.

Each year, park staff receive training in the identification and removal of the plant. Wherever the plant is identified, it is removed and its location mapped so that we can see any changes/trends in growth (e.g. where the plant is monitored, if and where new plants are sprouting).

Why does it keep coming back?

Many green heart-shaped leaves growing on the ground.Garlic mustard in its first year of growth

Like other invaders, garlic mustard is incredibly successful at spreading and multiplying.

These are some of the characteristics that allow this species to be so successful:

  • Seeds released from garlic mustard pods can remain viable in the soil for many years.
  • Their roots produce a chemical that alters the soil and can prevent native species from growing.
  • The plant grows at a faster rate than many native species, effectively outcompeting them for space and sunlight, which plants need to survive.

This means there is no short term solution and it is important that the removal program is carried out annually to keep the plant under control in the park.

2018 results: a double

Last spring, Arrowhead invited the public to help with some removal sessions. We hauled over 40kg (heavier than a large adult Algonquian wolf!) of garlic mustard from over 30 campsites, adjacent wooded areas and almost 1km of road.

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Pulling garlic mustard early in the season means fewer plants grow to maturity, which means fewer seeds later in the season.

Two Ontario Parks employees, one with a spray device

In the fall, we followed up on those sites with chemical spraying. Spraying regrown or diluted garlic mustard can kill it further and help keep the population under control.

Next spring, our staff will return to the treated sites to see which plants have returned and plan another removal blitz to keep this invasive species under control in the park.

What to do if you see garlic mustard in one of our parks?

Report it.

Find a staff member at the front door or Visitor Center and tell them what you saw, including the location. Staff can then confirm identification, map the location for park records, and dispose of the plant appropriately.

Guy in the woods, holding a multi-stemmed garlic mustard plantGarlic Mustard, shot in its second year of growth

Do not try to remove it yourself.

It is very easy to spread the seeds, so proper disposal is essential. Garlic mustard can also resemble several native plants, so please allow our staff to confirm that it is garlic mustard before removing any plants.

If you own private land and think you might have garlic mustard on your property (or are just curious to learn more), check out Ontario’s Best Management Practices for Garlic Mustard.

To help celebrate the 125th anniversary of Ontario Parks, parks across the province are hosting 13 stewardship programs to help protect biodiversity in provincial parks.