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Invasive Plants and Noxious Weeds

Why Invasive Plants and Noxious Weeds Matter

Invasive plants are non-native plants that spread easily, aggressively, and may displace or alter native plant communities. Invasive plants are recognized globally as the second greatest threat to biodiversity.

As per the Alberta Weed Control Act, municipalities are required to control the spread of noxious weeds. The City of St. Albert works to control invasive plants and noxious weeds in ways that do not affect other plants and surrounding areas.

Specific impacts of invasive plants include:

  • Disruption of natural ecosystem processes
  • Alteration of soil chemistry which prevents the re-growth of native plants
  • Increased soil erosion
  • Livestock and wildlife poisoning
  • Decreased habitat for native wildlife
  • Interference with forest regeneration
  • Allergic reactions

How Residents Can Manage Weeds

The most effective method of managing invasive plants/weeds is preventing their introduction and quickly responding to new occurrences. The first step in managing invasive plants is recognizing them. The following tips will help to maintain a healthy lawn and garden that can resist weeds:

  • Make sure you have 15-25 cm of loam (soil with roughly equal proportions of sand, silt, and clay) and/or compost to establish a healthy lawn
  • Aerate your lawn (fall and spring) and top-dress with loam to improve the soil surface
  • Keep grass height on the long side – 6 cm (2 ½ inches)
  • Crowd out the weeds by over-seeding your lawn
  • Maintain your gardens with native plants suitable for plant hardiness Zone 3
  • Practice companion planting. Certain plants like to grow closer to one another and provide benefits to each other such as repelling pests/weeds and replenishing soil nutrients

If you notice that weeds are growing in your lawn or garden, there are several measures you can take including:

  • Hand pulling/digging weeds. This is often the most effective way to eliminate weeds because you can pull both the weed and the root system
  • Mowing over weeds before they go to seed. This will help reduce the spread of the weed and in a few seasons can eliminate the weed altogether
  • Talking to your local gardening expert. In some cases, companion planting can help eliminate weeds because they don’t like growing close to certain plants
  • Applying an organic fertilizer which will help to promote root growth, improve your lawn’s colour and increase the resistance to disease and weeds. Organic fertilizers do not leach and run-off into our rivers, are non-toxic and non-corrosive which make them a healthier choice compared to traditional fertilizers.
  • Spraying weeds with herbicides is an option; however, we recommend this as a last resort.If you choose to use a herbicide try spot treating rather than treating your entire yard. Also, talk to local experts beforehand so they can tell you how to use the product properly and safely.

Report a Concern

If you have a concern about a noxious weed, please contact our Public Works team at 780-459-1557.

Noxious Weeds in St. Albert

Keep your eyes peeled for the Weed of the Week in the St. Albert Gazette and on the City's Facebook page and Twitter feed! The Weed of the Week identifies one of eight noxious weeds the City has identified as a threat to our community, how the City is controlling it and what you can do to help.

Purple Loosestrife

  • Stems are square, woody and grow up to 2 metres tall
  • Flowers are bright purple with wrinkled petals

Removal Tips

Orange Hawkweed

  • Stems are leafless with bristly hairs and grow 15 to 90 cm tall
  • Flowers form at end of stems in clusters
  • Orange-red flowers composed of square edged, notched petals

Removal Tips

Himalayan Balsam

  • Stems are smooth and grow up to 3 metres tall
  • Flowers are long in shades of pink

Removal Tips

Oxeye Daisy

  • Stems are smooth and grow up to 1.5 metres tall
  • Flowers are white with a yellow centre

Removal Tips

Garlic Mustard

  • Dark green kidney-shaped leaves; stays green throughout winter
  • Flowers are in clusters at top of the stem and have four white petals

Removal Tips

Dames Rocket

  • Stems branch at tip and grow .5 to 1 metre tall
  • Flowers are shades of lavender-pink through purple and white

Removal Tips

Leafy Spurge

  • Stems are arranged in clumps and grow up to one metre tall
  • Flowers are small and yellowish-green

Removal Tips

Common Burdock

  • Purple flowers and a red-tinged stem
  • Leaves are large, hairy and heart-shaped

Removal Tips

For a list of invasive species fact sheets and more information on invasive plants in Alberta, visit the Alberta Invasive Species Council.

How the City Manages Weeds

The City of St. Albert uses a variety of Integrated Pest Management (IPM) programs to manage the many natural risks, including invasive plants and noxious weeds. Whenever possible, preventative measures are used to promote natural biological controls; however when this is not possible, as a last resort, the City may opt to use a specific herbicide treatment for a targeted area.

Last edited: December 6, 2017

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