Invasive Plant Alert
Prevent the Escape of Aggressive Plants
A threat to BC’s resources
Wild flowers or Invasive Noxious Weeds?
Foreign plant species escaping from the garden or landscape can have a
devastating impact on native plants and animals. Please help in protecting the natural environment
of British Columbia!
BC’s noxious weeds are typically exotic or non-native plants that have
been introduced to this province without their natural predators. Left unchecked, these weeds
destroy our native plant and animal habitat. They are among the top cause for losses in the natural
diversity of our environment, and are devastating to the economy. Weeds cause crop losses
well in excess of $50 million annually in BC.
Impact
Invasive plants have the capacity to move into a habitat and reproduce so
aggressively that they displace the original vegetation. They:
- crowd out
native plants, including rare and endangered species
- destroy wildlife
habitat
- reduce crop yields (on average 10 to 15 %)
- reduce crop quality
(taint food products with off flavours, toxic berries, spines, etc.)
- poisonous weeds are a danger to humans, livestock, and wildlife
- dry weeds
create a fire hazard; tall weeds along roadsides create a traffic hazard;
aquatic weeds pose a danger to swimmers and boaters
- provide refuge for
insects and diseases that attack adjacent crops and beneficial plants
- lower
property value
- reduce aesthetics of an enjoyable landscape
- reduce soil
stability and water quality
- cause physical discomfort to recreationists due
to spines, burrs, prickles
Purple loosestrife, English ivy, Dalmatian toadflax, Scotch broom, field
scabious, Oxeye daisy, giant hogweed and Japanese knotweed (bamboo) are but a few examples of
horticultural plants that have escaped and caused extensive economic and environmental damage in
various regions of BC. They were introduced through the sale of seeds, cuttings, etc targeted for
the home gardener for use as birdseed, for wildflower landscapes or as medicinal herbs. Ragweed, a
plant that is quite rare in BC, has recently been found growing under bird feeders at a number
of locations.
Noxious weeds have gained a foothold in BC through accidental introductions
by various mechanisms including: wind and water; unloading of ship ballast;
hitchhiking on vehicles, boats and heavy equipment; contaminated crop seed; wildlife, etc. Seeds, cuttings or bulbs
of virtually any worldwide noxious weed are available through the mail or the Internet. These
plants are sometimes used for research purposes but many are also used for landscape or
medicinal/herbal purposes. Unfortunately, some noxious weed infestations have also resulted from
purposeful introductions as garden and landscape plants. Ideal characteristics for the garden, such as
adaptability, vigorous growth and establishment, self-seeding ability, and
persistence are the same characteristics that threaten our natural resources
once these plants escape the garden.
Legislation
In Canada, the Seeds Act regulates allowable weed seed content of crop seed
and the Plant Protection Act regulates import of a few parasitic plants.
Currently there is no federal noxious weed legislation that specifically
regulates the import of aggressive or potentially noxious plants for landscape
and garden use. The BC Weed Control Act places a duty on all land occupiers to
control noxious weeds listed in the Regulations. In BC, there are 47 plant
species that are classified as Noxious. These must not be transported to or
seeded in areas where they are not already established.
Non-native garden seeds
These are offered for sale with the best of intentions; the creation of a
pleasing, colourful landscape or for their herbal properties. Some of these
plants are classified as noxious in BC or are recognized as being so in other
jurisdictions. Some species are close relatives of known invasive plants and
may also have aggressive tendencies. In most instances the species offered for
sale are not a threat to the environment and serve their intended purpose
without threat to our natural resources.
Undesirable plant species
Deciding what plant species might be undesirable in a given area would be an
exceptionally difficult task. Each species would have to be judged on its
individual potential to escape and invade native landscapes. The following list
contains a few examples of aggressive ornamental or herbal species that have
escaped the garden and are available for purchase through various sources.
![](images/giantragweed.gif)
What Can You Do?
BE AWARE
Learn about the potential aggressiveness of what you buy through mail-order
seed catalogues, the Internet and other sources. Awareness is the key to
preventing further losses to BC’s biodiversity due to introduction of
invasive foreign plant material.
- Do not purchase legislated noxious weed seeds.
- Contain creeping plants. Grow
them in containers.
- Don’t let invasive plants go to seed.
- Control weeds
growing underneath bird feeders.
- Grow alternative plant material. (e.g.,
substitute less aggressive plants for purple loosestrife)
- Keep aggressive
plants from escaping your garden or landscaped area.
- Do not use roadside/idle
area plants in flower arrangements
To learn more about BC’s noxious weeds contact your local BCMAFF office, or
visit our website at:
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