is a Noxious Weed
term "noxious weed" is not merely a descriptive term, but a legal
term that mandates control of certain weeds at a Federal, State, or
local level. In
Colorado, noxious weed control is required by state
law. The Colorado Noxious Weed Management Act was passed into law
in July, 1990, (CRS 35.5.5-101 et. Seq). The law states that certain
noxious weeds pose a threat to the continued economic and environmental
value of the land in Colorado and they must be managed by all landowners
in the state.
wildfire, an explosion in slow motion, a vegetative cancer. These
phrases refer to the ecological threat, noxious weeds. Noxious weeds
are like biological litter, but imagine trash that grows and expands
then it’s thrown along a trail or roadside. Noxious weeds share three
general characteristics: nonnative, often poisonous or unpalatable
to wildlife and livestock, and are superior competitors that have
tremendous ability to displace native vegetation.
weeds establish themselves in soil disturbed by construction of highways,
buildings, and trails. They tend to produce an abundant amount of
seeds. The seeds of the original population are spread by livestock,
machinery, vehicles, wind, water, people and wildlife.
of the noxious weeds of this area came from Eurasia, from habitats
similar to those of the drier sites in the county. They are well suited
to this climate. With no natural enemies in this country, noxious
weeds quickly establish, and are difficult to eradicate. They severely
impact ranching and agriculture, recreational values of natural areas,
and most of all, they severely compromise the biointegrity and biodiversity
of ecosystems in the state.
bindweed (Convolvulus arvensis), is a perennial broadleaf
plant that reproduces by seeds and horizontal roots. Leaves are 1
to 2 inches long and are shaped like arrowheads. Flowers are bell
or trumpet-shaped, white or pink and about ¾ to 1 inch broad. Seeds
remain viable for up to 40 years.
thistle (Carduus nutans), is a biennial broadleaf plant
that reproduces solely by seed. Leaves are 6 to 14 inches in length,
dark green, and spiny with white margins. Flowering heads are terminal,
solitary, usually nodding, and deep rose in color. Broad spine-tipped
bracts are located underneath flowering heads. Mature plants can grow
as tall as 6 feet and appear solitarily or with several stems from
thistle (Onopordum acanthium), is another biennial
broadleaf plant similar to musk thistle. Mature plants can grow up
to 12 feet tall and have a large, fleshy taproot. Stems are numerous,
branched, and have broad, spiny wings. Flower heads are numerous,
violet to reddish in color, with spine-tipped bracts beneath. Leaves
may be up to 2 feet long, and 1 foot wide, and covered with dense
hair giving the leaves a gray-green appearance.
loosestrife (Lythrum salicaria), is a perennial plant
that reproduces by seeds and rhizomes. Leaves are lance-shaped, entire,
and whorled. Showy flowers are rose-purple in color with 5 to 7 petals
arranged in long racemes. Plants can grow 6 to 8 feet tall and become
taller and bushier as the
matures. A single flowering stalk can produce 300,000 seeds that remain
viable for up to 20 years.
spurge (Euphorbia esula), is a deep-rooted perennial
plant that reproduces by seeds and by roots (reaching about 30 foot
depths in the soil). Capsules can send seeds up to 15 feet from the
parent plant, while roots can produce as many as 300 vegetative buds.
Leaves are alternate, linear, and 1 to 4 inches long. Flowers are
yellowish-green, small, numerous clusters, enclosed by heart-shaped
bracts. The entire plant contains a white, milky latex.
thistle (Cirsium arvense), is a perennial broadleaf
plant that reproduces primarily by roots but also by seed. Leaves
are set close on the stem, dark green, and contain numerous, sharp
spines. Flowers are small, about 1 centimeter in diameter, and white
to purple in color. Mature plants grow 2 to 4 feet tall.
most effective plan for managing noxious weeds combines several control
methods in a consistent, integrated management program. The plan must
take into account the needs of the desirable plants, the nature of
the plant pests, and the needs of the property owner and land users.
An Integrated Weed Management (IWM) program consists of a variety
of combinations of the following methods:
Prevention – Good management will help keep desirable vegetation healthy
and weeds under control. Buy only weed-seed-free hay, plant only
certified seed, wash your vehicle and equipment after being in
a weed-infested area, monitor your property and respond quickly
to new weed infestations.
Cultural – Cultural controls seek to control weed problems by establishing
desired plant species. Cultural techniques manipulate the plant
community through cultivating (cutting through and turning over
the soil), re-seeding, fertilizing and irrigating.
Biological – Biological control agents are organisms (usually insects)that are
deliberately introduced to an area to control noxious weeds. The aim
of biological control is not eradication, but rather to exert enough
pressure on a weed to reduce its abundance to acceptable levels. Biological
control agents are most useful for reducing seed production or weakening
plants in large, dense noxious weed infestations where other control
methods are not cost-effective.
Grazing – Landmanagers can use cattle, sheep and goats to
selectively overgraze certain weed species, thereby weakening
them. In cases where desirable native species are not attractive
to livestock, grazing may favor growth of native species over
weeds. Livestock and wildlife can carry and spread weed seed
on their coats or in their feces; avoid moving livestock from
weedy areas to weed-free areas when weeds are producing viable
Mechanical – Techniques like mowing, tilling, hand-pulling, or burning
can physically disrupt plant growth.
Herbicides – Herbicides are chemicals that kill or control targeted plants.
They can be safe and effective when applied properly. Herbicides
decrease growth, seed production, and competitiveness of susceptible
Weed Regulations in Adams, Arapahoe, and Weld Counties.
mentioned in the beginning of this section, noxious weed control is
required by state law – the Colorado Noxious Weed Management Act.
All landowners in the state must manage noxious weeds. The law further
directs local government (cities and counties) to develop integrated
weed management plans for their jurisdiction. By complying with this
law, you are not only retaining or possibly increasing your property
value, you are being a good neighbor and following the Code of the
West as well. Team up with neighbors in the fight against noxious
County-Adams County established a Noxious
Weed Management Plan and a Noxious
Weed Enforcement Policy in March 1997. The Policy mandates that
all landowners in unincorporated Adams County control the designated
noxious weeds on their property. The weed species designated as noxious
in Adams County are; leafy spurge (Euphorbia esula), purple
loosestrife (Lythrum salicaria), field bindweed (Convolvulus
arvensis), Canada thistle (Cirsium arvense), musk thistle
(Carduus nutans), Scotch thistle (Onopordum acanthium),
diffuse knapweed (Centaurea diffusa), spotted knapweed
(Centaurea maculosa), and Russian knapweed (Acroptilon repens).
County- Since January 1, 1998, Arapahoe County landowners are
required to control any plants on the County’s noxious weed list.
This list includes the same species as the Adams County’s noxious
weed list but with the addition of whitetop (Cardaria draba),
dalmatian toadflax (Linaria genistifolia), and yellow toadflax
County-Weld County established an Undesirable Plant Management
Plan which was adopted as County Ordinance #169 in May, 1992. The
ordinance was revised in April, 1996, as County Ordinance #169A. The
County Ordinance mandates that all landowners in unincorporated Weld
County control the designated noxious weeds on their property. The
Weld County Noxious Weed List is similar to that of Adams Counties
with one exception, the addition of dalmatian toadflax (Linaria
County Extension - Colorado Noxious Weed Information
County Weed Department: 303-637-8115
County Weed Department: 303-738-7861
County Weed Department: 970-356-4000 ext.3770
- A Manual for Success, 2nd Edition
information on this and many other Small Acreage topics are now available
- A Manual for Success, 2nd Edition
a copy of this book please contact the Adams County Small Acreage Coordinator