Recognizing that invasive, non-native plants threaten the environment by disrupting the ecological balance of plants, animals, soil and water (not to mention the aesthetics), the Forestry Committee conducted their first "Thistle Thrash" in 1992 on Canada thistle by pulling, cutting and bagging plants. This was followed in 1993 with another "Thistle Thrash" and in 1994 with a full-scale weed assault by first mapping all the locations on Open Space of the noxious weeds mandated for control by the 1990 Colorado Undesirable Plant Management Act (HB 90-1175).

During the period between 1992 and today, numerous community-wide educational efforts have been made to inform everyone of the need for weed control on both public and private lands. A Noxious Weed Control Handbook, complete with color photos, was designed, published and distributed to each household. Numerous articles on weeds and their control have been published in the Genescene. A Forestry Committee "Weed Posse" was initiated whereby 82 private lots were assessed and the "top 10" weed infested lots were selected for individual contacts. Weed samples, fliers and picture postcards have been put on display for public review during each July 4th celebration. Due to the expanse of the weed populations, private contractors have been hired each year to apply herbicides to large patches of weeds close to roadways. In-house staff has likewise applied herbicides via backpacks for several weeks each year to weeds in far-from-the-road infestations. Mechanical control (hand-pulling, chopping, cutting, etc.) have been applied to several selected weed populations covering more than 10 acres of Open Space. Biological control agents (weed eating insects) have been released for Canada thistle and Musk thistle. Other control agents have been released nearby and will undoubtedly find their way here as well. Efforts to date include the more than 90% reduction of plant numbers in certain weed populations and the general increased awareness of the problem within the community. It is anticipate that all of these means of weed management will continue unabated as the issue of alien weeds has gained national prominence.

Other Weeds of Concern

  • Common mullein (Verbascum thapsus)
  • Cypress Spurge (Euphorbia cyparissias)
  • Dalmatian toadflax (Linaria genistifolia)
  • Scotch thistle (Onopordum sp.)
  • Yellow toadflax (Linaria vulgaris)
  • Myrtle spurge ( Euphorbia myrsinites)
  • Russian olive (Eleagnus angustifolia)
  • Oriental clematis (Clematis orientalis)

Jefferson County Noxious Weed List -
weeds that must be controlled

  • Leafy spurge (Euphorbia esula)
  • Diffuse knapweed (Centaurea diffusa)
  • Russian knapweed (Acroptilon repens)
  • Canada thistle (Cirsium arvense)
  • Musk thistle (Crduus nutans)
  • Myrtle Spurge (Euphorbia myrsinites)
  • Purple loosestrife (Lythrum salicaria)
  • Yellow starthistle (Centaurea solstitalis)
  • Common teasle (Dipsacus sylvestris)
  • Orange hawkweed (Hieracium aurantiacum)
  • Hoary Cress (Cardaria spp.)
  • Hound tongue (Cynoglossum officinale)

The most effective control for any particular weed depends largely on its biology. Some weeds can be eradicated by merely pulling them up; whereas others are merely encouraged to spread by that same action. Know your weed before you attempt to control it. Information and recommendations for weed control can be found in the Oxley Library, by calling the Open Space Department or by contacting Jefferson County Weed and Pest Department.