Enlarged images of carpet burweed collected from Beacon Hill Park, Victoria, April 10, 2006.
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How the Royal BC Museum Herbarium Fights Invasive Species
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By Dr. Ken Marr, Curator of Botany
ccidentally or deliberately, humans move plants around the planet. We call them “weeds” if they grow where we don’t want them and “invasive” if they spread, their numbers unchecked by the herbivores and diseases that keep them in control where they originate. Many cannot survive or spread in their new homes without human care—think of pansies and petunias. But a few, the invasives, spread into landscapes disturbed by human activity, like urban areas, roadsides and agricultural fields. Others invade natural habitats, altering ecosystems simply by occupying the spaces in which native species occur, in turn impacting the birds, insects and mammals that depend on those native species for food. Millions of dollars are spent to control agricultural weeds, although ironically, the crops we grow are not native to BC and could be considered “invasive” themselves. There are about 2,400 native plant species in BC. About 900 are nonnative, and of these a few dozen are invasive. Invasive species arrive by various means, intentionally or unintentionally: as contaminants in grains, with the nursery trade, as livestock forage or as ornamentals. A surprising source is commercial wildflower seed mixes. These certainly contain wildflowers, but most are from Europe or Asia, not British Columbia. 28
