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Weed of the Week: Hoary Alyssum

As you are driving through BC’s Okanagan, Cariboo, Boundary, Thompson and Kootenay areas, you may notice a small white flower sprinkled along roadsides or spread across a field like sifted white power. This is hoary alyssum (Berteroa incana). Declared a noxious weed under the BC Weed Control Act, hoary alyssum is a plant that is believed to have invaded North America by contaminants of clover and alfalfa seed. 

This plant is found on dry conditions and creeps into meadows and pastures. Another favourite spot to thrive is disturbed, open areas. Hoary alyssum is commonly found rooted in the sandy soils of construction sites, slopes alongside train tracts, or dusty roadsides.

Hoary alyssum grows as tall as 1.1 m, proudly displaying its white flowers. The plant blooms from early spring to late fall. The plant’s slender taproot is buried deep and progresses upward to a stem which is showered with star shaped hairs.  Hoary alyssum’s leaves are grey with a rough texture similar to sandpaper.

The weed’s seeds are dispersed by wildlife, birds, machinery, vehicles, and footwear. Seeds also spread by a plant’s valves in the seed pod or as a contaminate of hay. Hoary alyssum seeds have the potential to remain dormant for as long as nine years.

Property value decreases by the presence of hoary alyssum. In addition, while not affecting other livestock, the plant can be potentially damaging for horses. The weed is toxic to many horses and can inflict fever, limb edema, and lamintis. In severe situations, if hay containing between 30-70% hoary alyssum is consumed, it can be fatal.

 Although hoary alyssum has no biological agents, both mechanical and chemical controls may be utilized to gain effective management of the plant. In order to prevent the spread of this weed you can take simple precautions such as avoiding storage and parking in contaminated locations as well as removing plant material from vehicles, clothing, and equipment before leaving the site.

To find out more, click here or phone 1-888-WEEDSBC to report sightings.

In Your Words...

  • “Thank you for orchestrating access to the Hot Spots crew for GINPR.  This crew allowed us to move the restoration project on Princess Margaret ahead by months if not by years.”

    Wayne Bourque, Superintendent of Gulf Islands National Park Reserve, Parks Canada

  • “Working with the Hot Spots crew in Saanich in 2010, we practiced different methods to treat knotweed with glyphosate using the injection gun on several sites. With these skills I was able to implement Saanich's first knotweed eradication pesticide treatment program for private properties.”

    Donna Wong, Environmental Stewardship Officer, District of Saanich

  • “Our crew has finished their work at Fort Rodd Hill National Historic Site and Gulf Islands National Park Reserve. I want to thank you, on behalf of Parks Canada, for providing the crew to us. They were well-trained and got a lot of important restoration work done in our nationally-important heritage areas.”

    Brian Reader, Species at Risk Manager, Parks Canada

  • “Parks Canada and Canadians have benefited from the partnership to have on-the-ground Hot Spots crews, and we would be happy to work with a crew in the future at one of our many national parks and national historic sites that are in need of invasive plant management.”

    Brian Reader, Species at Risk Manager, Parks Canada

  • "We had a great hike at Kenna Cartwright Park. The kids built a snowman and we all enjoyed the views. The outreach worker showed us some plants that don't belong in the park, gave us info about them and what to do about them, and gave us all some cool gifts from the Invasive Plant Council. Thank you!"

    Susan Hammond, Kamloops Young Naturalist Club

  • “I am impressed with the coverage of the GIS mapping data now available. I will be developing an Invasive Species Management Plan for Pacific Spirit over the next several years and these maps will help as a coarse indication of current conditions, and in guiding initial inventory and monitoring efforts.”

    Markus Merkens, Pacific Spirit Park area manager, Metro Vancouver

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