Ornamental Weeds

Listed below are ornamental plants formerly available for purchase at nurseries, now on the state's prohibited sales list and categorized as List B species and List C species with the Colorado Department of Agriculture. These ornamental weeds have escaped to natural areas in Larimer County and become invasive plants. Please see the article Ornamental Weeds for more information. Other escaped ornamental species already listed in this website under the List A or List B species on the Larimer County Management Plan are: Cypress spurge, Dalmatian toadflax, dyer's woad, Mediterranean sage, myrtle spurge, purple loosestrife, tamarisk, teasel, and yellow toadflax.

Descriptions, management recommendations and methods of control are listed below.

Black henbane (Hyoscyamus niger)

Black henbane is an annual or biennial forb of the nightshade family.

Black henbane grows to 6 feet tall and produces a brown-yellow flower with a purple center. This plant was introduced to the U.S. for ornamental and medicinal uses. Black henbane contains alkaloid compounds that are poisonous to livestock and humans. Locally, this escaped ornamental is known to exist in the Estes Valley.

Black henbane reproduces by seed only, so management methods need to occur prior to seed set. Herbicides proven to be effective for control of black henbane are Escort, Telar, and Tordon.

There are no insect biocontrol agents available for control of this weed.

Mowing only provides temporary control of this annual/biennial, which will re-grow and set seed from a reduced height. Hand pulling or digging is effective. If plants have flowered be sure to bag and dispose of properly to prevent seed dispersal.

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Bouncingbet (Saponaria officinalis)

A perennial forb that reproduces from seed or rhizomes. Also known as soapwort, this plant grows to 3 feet tall and produces pink-lavender flowers. Bouncingbet is found in sporadic patches around cities and towns in Larimer County. This plant is toxic to livestock.

The most effective herbicides for controlling bouncingbet are Escort and Telar.

There are no insect biocontrol agents available for control of this weed.

It has been reported that digging this shallow-rooted perennial can be effective if all rhizomatous material is removed.

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Chicory (Cichorium intybus)

A tap-rooted simple perennial that reproduces only by seed.

Chicory grows to 3 feet tall and produces a lavender-blue flower. The leaves of this plant have been used as salad greens, and the root as a coffee substitute. Chicory is not common in Larimer County but has become an invasive plant along roadsides and pastures in Boulder and Jefferson Counties. Potentially, it is a threat to rangeland and pasture here.

The most effective herbicides for controlling chicory are Escort and Telar.

There are no insect biocontrol agents available for control of this weed.

Digging or hand pulling this tap-rooted plant is a very effective method of control.

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Dames rocket (Hesperis matronalis)

A biennial or short-lived perennial of the mustard family that grows to 4 feet tall and produces showy purple flowers. Dames rocket is found within and on the outskirts of many mountain towns, and is becoming a species of concern along the Poudre River Canyon and Big Thompson Canyon. The plant is a prolific seed producer that grows from a large rosette that can crowd out other vegetation.

The most effective herbicides for controlling dames rocket are Escort and Telar.

There are no insect biocontrol agents available for control of this weed.

Digging or hand pulling this tap-rooted plant is a very effective method of control. If in flower, be sure to bag and dispose to prevent seed dispersal.

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Oxeye daisy (Chrysanthemum leucanthemum)

A simple perennial that reproduces by seed and lateral roots. Oxeye daisy grows to 2 feet tall and produces showy white flowers. This escaped ornamental plant has become an aggressive invader of pastures and mountain meadows in Boulder, Jefferson and Grand Counties. Locally this plant is found in the Estes Valley and is a threat to the plant diversity in Rocky Mountain National Park. Surveys conducted in 2011 have mapped serveral infestations on USFS land that were previously unknown. In 2012, we will continue treatments with the ultimate goal of elimination in these sensitive areas.

The most effective herbicides for controlling oxeye daisy are Escort and Telar.

There are no insect biocontrol agents available for control of this weed.

Digging or hand pulling this shallow-rooted perennial can be an effective method of control. If in flower, be sure to bag and dispose to prevent seed dispersal.

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Scentless chamomile (Matricaria perforate)

An annual plant that looks very similar to oxeye daisy. Scentless chamomile grows to 2 feet tall and produces a showy white flower. It has very thin, finely divided leaves, which distinguishes it from oxeye daisy's broader, spoon-shaped leaves.

The most effective herbicides for controlling scentless chamomile are Escort and Telar.

There are no insect biocontrol agents available for control of this weed.

Digging or hand pulling this shallow-rooted annual can be an effective method of control. If in flower, be sure to bag and dispose to prevent seed dispersal.

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