The City’s phased plan to reopen facilities and services is based on our commitment to protect City staff and residents, and in adherence with the most up-to-date State of Colorado and Boulder County public health orders. To learn more about which City facilities have reopened or plan to reopen, visit the COVID-19 webpage.

Invasive Species

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 Myrtle Spruge
City of Louisville Urges Landowners to Remove Myrtle Spurge!

Myrtle spurge is a noxious weed which can invade open space and residential landscapes and is dangerous to people, wildlife, and native plants.  This low-growing perennial plant is 4 to 8 inches tall with fleshy blue-green triangle-shaped leaves and yellowish-green flower-like bracts in the spring. The leaves and stems have toxic milky latex which can cause severe skin irritation and is poisonous if ingested.  Spreading rapidly from gardens to natural areas, myrtle spurge can out-compete native vegetation and reduce forage for wildlife.  It is a List A noxious weed which is required for eradication by the Colorado Noxious Weed Act (C.R.S. 35-5.5-101-119).  If you have myrtle spurge on your property, please remove it by hand-pulling, digging, or treatments with herbicides containing 2, 4-D or Roundup. Wear protective gloves, long-sleeved shirt, and glasses when handling the plant and carefully dig up as much of the root system as possible and dispose of in a garbage bag (tie up the bag so that seeds cannot escape).  Do not compost and do not plant myrtle spurge.  If you need help identifying myrtle spurge or have any questions, please contact the Open Space Division at 303-335-4742.

Noxious Weeds
Noxious weeds are one of the most serious threats facing the City of Louisville Open Space. Noxious weeds out compete native vegetation for resources such as sunlight, water, growing space, and soil nutrients. They are able to do so because they have few natural predators or diseases, are not as palatable to wildlife and livestock as native vegetation, have deep and extensive root systems which more easily sequester water and nutrients, produce thousands of seeds per plant, and some weeds have allelopathic capabilities which inhibit the growth of surrounding native plants.

Myrtle-Spurge    Perennial-Pepperweed
Myrtle Spurge                            Perennial Pepperweed

Once established noxious weeds cause severe ecological and agricultural impacts to our Open Space properties by decreasing biodiversity, diminishing habitat and forage for wildlife, increasing soil erosion, and decreasing crop yield. Additionally, management of weed control efforts requires a considerable amount of funding and time for planning and implementation.

Aquatic Nuisance Species
Aquatic nuisance species (ANS) pose a serious threat to our waterways. They are invasive plants and animals that live outside of their native habitats. Due to a lack of natural controls, ANS spread and reproduce rapidly causing serious damage to our local ecology and commercial and recreational activities. Their financial impact can reach billions of dollars throughout the United States.

Negative Impacts:

  • Reduce native and game fish populations
  • Clog boat engines
  • Make lakes and rivers unusable to recreation
  • Significantly impact the operations of drinking water plants and power plants by clogging pipes and other equipment
  • Destroy aquatic ecosystems
  • Reduce property values

Fortunately, the City of Louisville does not currently have any ANS in our waterways but many are nearby in locations where you may recreate. It is important that we prevent their introduction into Louisville. Please review the following educational materials to learn how you can help.

    For additional information, please contact Ember Brignull, 303.335.4729.


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