Garlic mustard
Invasive garlic mustard can take over forests, harming native understory species (Photo by NCC)
No friend to our forests
Garlic mustard, a highly invasive plant, has been spotted on Nature Conservancy of Canada (NCC) properties across Ontario.
Brought to North America in the 1800s, this invasive alien plant is now spreading across the continent at a rate of 6,400 square kilometres per year — that's an area 10 times the size of Toronto!
The success of garlic mustard is multi-faceted. Aside from having no natural enemies in North America, garlic mustard is an early riser. It takes advantage of the open canopy of springtime deciduous forests and the first rays of sunlight after the winter snow has melted, getting a head start on the native plants. Garlic mustard can change a forest's composition over time, creating a more favourable environment for itself, while driving other species out of the understory. This can even impact what trees grow in the forest, as garlic mustard can interfere with the germination of tree seeds.
In Ontario, garlic mustard occurs in the southern and eastern parts of the province and as far north as Thunder Bay.
What is garlic mustard?
Identification
- Garlic mustard leaves emit a strong garlic odour when crushed.
Garlic mustard, Happy Valley Forest, ON (Photo by Miguel Hortiguela)
- First-year plants have small, scalloped kidney-shaped leaves.
- Second-year plants grow up to 1.2 metres tall, with triangular, toothed leaves and clusters of small white flowers in spring (April-May).
Impacts of garlic mustard
- Garlic mustard rapidly spreads to displace native wildflowers and tree seedlings.
- The roots release chemicals that interfere with vital fungi growth needed for native plants to access nutrients, changing the soil composition and making it more difficult for native plants to grow.
Control options
- Hand pulling (make sure to get the whole root) in early spring (April/May) or fall (late September/October).
- Mowing/cutting in May (after flowering but before setting the seeds) and repeat until end of the growing season.
- Clipping flower heads in May and repeat until the end of the growing season.
- Repeated control may be needed for several years. Seeds can survive for up to 30 years in the soil!
- Planting native species in disturbed soil will help reduce future garlic mustard invasions.
https://www.natureconservancy.ca/en/where-we-work/ontario/our-work/stewardship/garlic-mustard-ON.html
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