Colorado Noxious Weeds -- Part 1

By Marilyn Loser: 2013 November 6

Any noxious weeds in your garden? I have several plants that are on one of the four Colorado Noxious Weed (CNW) lists. According to the Colorado Department of Agriculture (CDA) website, a noxious weed is a non-native plant that meets one or more of four criteria. It “1) aggressively invades or is detrimental to economic crops or native plant communities; 2) is poisonous to livestock; 3) is a carrier of detrimental insects, diseases, or parasites; 4) is detrimental to the environmentally sound management of natural or agricultural ecosystems.”

I don’t think I have any on the List A. According to the CNW Management Program brochure,  List A weeds are “species whose distribution in Colorado is still limited.  Preventing new infestations is the highest priority. Eradication of all List A species is required by law.”  However, I wonder about my beautiful Loosestrife that I believe is (Lythrum virgatum), not the invasive Purple Loosestrife (Lythrum salicaria). Loosestrife is especially harmful in fresh-water environments, such as ponds, lake shores, ditches, and stream banks, as it replaces many native species.

In fact, Washington State prohibits the sale of all Loosestrife hybrids and cultivars. It justifies prohibiting all hybrids and cultivars by saying it is difficult to distinguish between the species and because there is reason to believe that virgatum has the potential to invade and spread within wetlands.  I did purchase my Loosestrife from a nursery many years ago.  I have the winter to decide whether I should do something about it!

List B contains species that are limited to portions of the state. According to the brochure, List B weeds “are designated for control in regions where they are not yet widespread.  Preventing new infestations is a high priority.  In areas where List B species have already become established, state noxious weed management plans are designed to stop their continued spread.”

Several List B weeds are easily found around Alamosa. The two I see the most are types of whitetop: Hoary Cress (Lepidium draba formerly called Cardaria draba) and Perennial Pepperweed (Lepidium latifolium). They both have lots of tiny white flowers and reproduce by seeds and by horizontal creeping roots.  I don’t remember seeing them until eight or so years ago and now they are abundant in empty lots and along roadsides in Alamosa.  I don’t know of anyone who grows whitetop on purpose and I definitely consider it a weed.

However, there are several other plants on the B List that folks grow intentionally. I have Russian Olives (Elaeagnus angustifolia), Yellow Toadflax (Linaria vulgaris), and Dame’s Rocket (Hesperis matronalis) – all of which I purchased from nurseries.  Russian Olives are a tree that does well in our harsh climate and I like the bluish leaf color and spring fragrance. I know I bought the Russian Olives before Colorado nurseries were banned from selling them. This may also be the case for the toadflax and rocket, but I’m not sure.  I may have purchased them in New Mexico. Colorado is one of only three states that bans rocket and there are eight states that ban toadflax.

More than 10,000 acres are infested (CDA’s word choice) by Russian Olives in Colorado according to the CDA map.  Alamosa County lights up as having many infected acres while Rio Grande County doesn’t. The Alamosa Department of Parks and Recreation is working to eliminate Russian Olives in our parks. I talked with Darrell Plane, Rio Grande Country Weed Supervisor, regarding Russian Olives.  He said the state’s position is still the recommendation that List B species be controlled or removed on public lands. He’s not pushing it in Rio Grande County as Russian Olives do well in the county and are used as wind breaks.

I used to see toadflax, which my wild flower book called Butter and Eggs, in the backcountry and I loved the light-yellow, snapdragon look. I thought I was adding a Colorado native to my garden more than 20 years ago. I haven’t been able to eradicate it from my garden and I’ve tried.  It has a very invasive root system and out-competes plants that I want to thrive.

Magenta Dame’s Rocket blooms in the spring and reminds me of the tall phlox that blooms later in the season. It has four petals while phlox has five.  It is considered public enemy number two on the Michigan noxious weed list. Writing from Kalamazoo, Rosemary Parker says, “Dame’s rocket is so hard not to love.” As are other noxious weeds. This column will be continued in two weeks.

“When the blood in your veins returns to the sea, and the earth in your bones returns to the ground, perhaps then you will remember that this land does not belong to you, it is you who belong to this land.”  Unknown