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Noxious Weeds on OSMP

Noxious Weeds on OSMP

Some of the plants listed in the gallery below are illegal to grow, cultivate and sell and are mandated for eradication. You can help by using native plants in your garden. The first step to eliminating noxious weeds is to know them when you see them. This allows you to eliminate them from your own land and gardens, and to avoid buying them as ornamentals. You may also spot them while hiking on OSMP: please report where you find a patch, since it may be new to our records. Once identified, the patch can be eliminated using integrated pest management methods described below. Remember, the plants pictured below are one of the greatest threats facing OSMP's ecosystems!

Noxious Weed Gallery

Russian OliveScotch ThistleBladder SennaSoapwort or Bouncing BetSulphur CinquefoilPerennial SweetpeaTamariskCommon TeaselDalmatian ToadflaxCanada ThistleCheatgrass or Downey BromeDame's RocketJointed GoatgrassHoundstongueDiffuse KnapweedPurple LoosestrifeMediterranean SageMyrtle SpurgeMusk ThistleOxeye DaisyMyrtle Spurge - The King of NoxiousnessMyrtle Spurge - The King of NoxiousnessMyrtle Spurge going to seedVolunteers and staff on OSMP work very hard to remove Myrtle Spurge from the land.It escapes from people's gardens and becomes an invasive pest.

See full photo set in the Photo Gallery


Weed Control on OSMP - Integrated Pest Management

Worrisome Weeds

Noxious weeds are a very serious threat to our native ecosystems and have been described as a "Biological Wildfire." Each year noxious weeds attempt to further invade OSMP ecosystems on both the plains and  foothills. What makes certain plant species "noxious" is that they are non-natives which can grow in a variety of ecosystems. Visit our Noxious Weed Gallery above to learn how to identify these plants and how to eliminate them from your land or garden!

What are we doing?

OSMP has an Integrated Pest Management Program which uses many different control techniques on different weed species. Grazing, burning, mowing, hand-pulling, flooding, insect introduction, reclamation and prevention are a few control techniques that are used on Open Space. Herbicides, applied at the lowest rates possible, are used as a last resort.

An example of Integrated Pest Management at its best can be found along South Boulder Creek, where the threatened Ute Ladies' Tresses orchid, is competing with Canada thistle, an aggressive "noxious" weed. OSMP has been controlling Canada thistle and helping the orchid flourish by combining spring cattle grazing, mowing and historical haying practices, with the release of thistle eating insects.

Many people are responsible for weed management on open space. A summer crew maps weed infestations; cuts, hand pulls and digs weeds; applies herbicides; and cuts down Russian olive trees. Over 1,000 acres of weeds are mowed every summer. Spring cattle grazing and releasing insects distributed by the Colorado Department of Agriculture also keep certain weeds under control, reducing the need for herbicides. The key to Integrated Pest Management is to map each infested area and monitor the successes and failures of different control techniques.

Why not let nature (and evolution) take its course?

Protecting native ecosystems is central to OSMP's mission. We cannot stop the spread of noxious weeds everywhere, but we can preserve areas where native plants thrive as they have for millions of years before we introduced exotic species to Colorado.

What advantages do noxious weeds have over the natives?

A noxious weed is an introduced plant species that spreads very quickly, displacing native plants and altering local ecology.

  • These weeds offer little or no nutritional value to wildlife so they are not subjected to grazing pressure.
  • They have not evolved in this area so they have no predators (e.g. insects or diseases) to keep their populations in check.
  • They vigorously invade disturbed areas such as roadsides and new construction areas.
  • The absence of fire and grazing give noxious weeds another competitive advantage. Through urbanization the positive effects of periodic fire and grazing by populations of buffalo, antelope, and deer have diminished. These ecosystem "treatments" are known to stimulate grassland health and diversity.
  • Some noxious weed species like diffuse knapweed produce secondary metabolic compounds, which actually inhibit the germination of seeds in the immediate vicinity of the plant. This action is known as allelopathy.
  • The methods for seed dispersal in noxious weed species are numerous and highly effective. These plants also incorporate tremendous seed production with dispersal methods making each plant a source of thousands of viable seeds.

How can you slow the spread of noxious weeds?

The public plays a crucial role in slowing the spread of noxious weeds. The following are some simple guidelines everyone should follow.

  • When gardening and landscaping, make sure the plants or seeds you buy are not invasive exotics - see the gallery below.
  • Volunteer with OSMP to help us eliminate noxious weeds!
  • When hiking in or out of any park system take the time to check your pants, socks, and shoes for seeds that may have attached themselves to your clothes. Discard the seeds in a trash can. By doing so you ensure that the seeds are not being transported to a new location previously free of noxious weeds.
  • Take the time to educate yourself and others about noxious weeds.
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