Kelly Uhing
State Weed Coordinator - Colorado
In these
times of drought, the use of xeriscape plants in the garden are highly
recommended. While this is a wise idea for consumers to adopt, they
must be careful as to which drought tolerant plants they select to be
their next garden beauty. Most plants used for landscaping purposes
lack the ability to proliferate outside of the cultivated environment
of the home garden. Some plants however, were imported to the United
States for their aggressive growth habits, xeriscape potential, or re-seeding
capabilities. These plants are known as “Invasive Ornamentals”. The
very traits that make these plants desirable for a garden or landscape,
may also enable them to thrive outside cultivated areas and become fierce
competitors with our native vegetation. People seeking color, vigor,
and something special for their gardens have unwittingly brought these
non-native species into our environment. Unfortunately, most individuals
don’t realize that they may have opened a Pandora’s box in their plantings.
These non-native, aggressive plants quickly escape and begin the demise
of our native plant communities and some can be hazardous to humans. Myrtle spurge, for instance, contains
a milky sap that is highly caustic to the skin. If children are playing
in an area where this plant is growing and get the sap on their skin,
painful rashes and blisters will soon follow.
A major hurdle in stopping the spread of Invasive Ornamentals is the
misconception that something attractive can’t be a weed. On the contrary,
species like oxeye daisy, myrtle
spurge, and Russian olive have proven to be very ecologically damaging
and difficult to control once unleashed on our native landscapes. Wildflowers
such as Colorado Blue Columbine, our state flower, can’t compete with
invasive ornamental plants for nutrients, sunlight, and water. As a
result, our biologically diverse grasslands, mountain meadows, and wetlands
are in danger of being overrun by invasive ornamental plants. Fortunately,
there are plant choices available to the home gardener that provide
similar colors and growth habits to these invasive ornamentals, but
not the problems associated with them.
In 1999, the Colorado Department of Agriculture has adopted what is
called the Colorado Nursery Act. Within this Act, there is a list of
weeds that are prohibited for sale in Colorado. This list includes many
invasive ornamentals and can be viewed at http://www.ag.state.co.us/DPI/Nursery/NurseryRules.pdf.
Colorado nurseries or garden centers are required by law not to sell
or contaminate nursery stock with plant species that are included on
this prohibited weeds list. Some of the species included are Russian
olive, myrtle spurge, oxeye
daisy, bouncingbet, dame’s
rocket, purple loosestrife, and
common St. Johnswort.
Unfortunately, there are still quite a few wildflower seed mixes that
contain invasive ornamental plants. Even though it is unlawful to sell
these plants or seed mixes containing noxious weed/invasive ornamental
seeds, it is still possible to purchase them at quite a few chain stores
in Colorado and on the internet. If you see these plants or their seeds
for sale, please contact the Colorado Department of Agriculture at 303-239-4153.
Think native when choosing drought-tolerant plants for the garden. Contact the Colorado Native Plant Society for a list of native plants
that do well in a garden environment. There are also many non-native
plants that aren’t invasive and will do well in the garden. Ask your
local garden center experts for alternatives to invasive ornamentals.
They’ll be glad to help you.
