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Nature Speak

Purple loosestrife, Poster child of invasive weeds

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By Bob Brett and Veronica Woodruff

Whistler Naturalists and Whistler Fish Stewardship Group

If we had a rogue’s gallery of unwanted plants, purple loosestrife would certainly be one of the stars. This disarmingly attractive plant, nicknamed the "beautiful killer," invades wetlands and is extremely difficult to remove once it gets a foothold. The bad news is that purple loosestrife has made its way to Whistler.

One flowering purple loosestrife was found last week at the edge of the Fitzsimmons Creek Wetlands, south of the Boot Pub, during a plant survey conducted for the Whistler 2010 Biodiversity Inventory.

Although one plant may not seem to be much cause for concern, purple loosestrife seldom travels alone. Like all invasive plants, purple loosestrife is an ambitious and aggressive grower. Each plant produces millions of seeds and can also reproduce from small root fragments.

If purple loosestrife is allowed to reproduce unchecked, it will quickly dominate a wetland. The main concern is that it displaces the native vegetation that provides food and shelter for a wide variety of wetland creatures, such as waterfowl, fish, amphibians, and water-loving mammals like the muskrat.

Purple loosestrife ( Lythrum salicaria ) looks a bit like fireweed from a distance, with similarly-coloured pink-purple flowers. The main differences are its square stems, pairs of leaves on opposite sides of the stem, and wetland habitat. It was introduced to North America in the late 1800s, either inadvertently in ship ballast or as an ornamental.

It is illegal to sell or purchase purple loosestrife in many provinces and states. Unfortunately, there is no prohibition in B.C. (except in Comox) and some misguided nurseries or seed catalogues may still sell it. Even though some cultivars of purple loosestrife are advertised as sterile (under names like Morden Pink, Morden Gleam or Dropmore Purple), recent research has shown this to be incorrect. It is therefore safest to avoid any loosestrife.

If you have purple loosestrife (or any other invasive plant) in your garden, you should immediately remove it by hand digging of the roots. The roots should be thoroughly dried before disposal. If in seed, the whole plant should be placed in a dark garbage bag, tightly tied, and taken to the landfill. Ideally, the plant should be burned to prevent dispersal of the seeds. If you see purple loosestrife in a local wetland or need help with disposal, please notify the RMOW fish technicians at 604-935-8323.

Other invasive species to yank out of your garden include Scotch broom, foxglove, yellow flag ( Iris pseudacorus ), bluebells, oxeye daisies, and many of the introduced mustard species.

Whistler is lucky to still retain much of its native flora, unlike much of Vancouver Island, the Lower Mainland, Sunshine Coast, and Interior B.C. Preliminary results of the biodiversity inventory suggest this may be changing as invasive species move in at ever-higher densities. Vigilance is needed to keep the invaders at bay.

For more information on purple loosestrife and the huge problem it poses, type the name into your internet search engine. Most of Google’s 131,000 hits on purple loosestrife contain the same message: just say no.

Upcoming Events:

Monthly Bird Walk, Saturday, Sept. 2, 7 a.m. Join Whistler experts in the monthly update of our feathered locals. Meet at the bottom of Lorimer Road at the Catholic Church.

Kokanee Spawning, Wednesday, Sept. 7, 6:30 p.m. Tour the River of Golden Dreams with RMOW fisheries technician Veronica Woodruff to learn about Kokanee spawning and to discuss elements of environment balanced with recreation. Meet at the bottom of Lorimer Road near the Catholic Church.

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