Download San Luis Valley Weed Management Association

Mission: The San Luis Valley Weed Management
Association is a public and private partnership
created to promote awareness and management of
noxious weeds through local and regional
initiatives in the SLV area.
This attractive succulent not only has pretty
yellow flowers in the springtime, it harbors a
dangerous secret: its sap, also called milky
latex, can cause severe health problems.
Myrtle spurge can cause respiratory problems
in addition to skin irritation. The plant is toxic
if ingested.
For these reasons it is a plant that should be
eradicated on all properties.
Invasion of L. salicaria into a wetland can result in
the suppression of the resident plant community
and the eventual alteration of the wetland's
structure and function. Large monotypic stands
of L. salicaria jeopardize various threatened and
endangered native wetland plants and wildlife by
eliminating natural foods and cover. Dense plant
establishments in irrigation systems has impeded
the flow of water

This is an aggressive species that has invaded millions
of acres of rangelands in the western United States.
Cattle feeding on it may be poorly nourished and can
be damaged by the spiny heads. Horses may be
poisoned and develop chewing disease.
Bull thistle prefers sunny, open areas and can tolerate a wide
range of conditions, from moist to dry soils, and is typically
found in disturbed areas such as roadsides, trails, logged areas,
vacant land, pastures and cultivated land. Overgrazed pastures
are susceptible to bull thistle encroachment, and it can
sometimes form dense stands that reduce productivity and
stocking levels. Bull thistle may also dominate forest clear cuts
and reduce growth of tree seedlings.
Canada Thistle is a broadleaved
weed with creeping roots that extend up to 17 feet (5
m) horizontally and 20 feet (6 m) deep.
Unlike most other thistles, Canada Thistle (Cirsium
arvense) is a perennial.

Black henbane is a cultivated
ornamental plant and that
has spread throughout the
United States. It contains
hyoscyamine and other
alkaloids which have been
known to cause occasional
livestock poisoning. It is also
considered a poisonous plant
to humans.
In the past 25 years Chinese clematis has
spread especially rapidly, becoming weedy
and constituting a threat to young trees and
native shrubby and herbaceous species (Flora
of North America Editorial Committee 1997).
It has been a common weed of roadsides and other
disturbed areas and recently has begun to invade
valuable agricultural lands in the San Luis Valley. Viable
seed is spread easily thru roadside mowing and in many
other ways.

Mature plants are
strongly competitive,
especially with shallowrooted perennials and
winter annuals.
Dalmatian toadflax
causes negative impacts
in pastures, rangelands,
and natural areas,
where it outcompetes
natives or other
desirable species.
DAME’S ROCKET IS A TALL,
SHOWY, SHORT LIVED PERENNIAL IN
THE MUSTARD FAMILY. A PROLIFIC
SEED-PRODUCER, IT HAS ESCAPED
FROM GARDENS AND NOW INVADES
ROADWAYS, WOODLAND EDGES AND
FOREST INTERIORS.
DIFFUSE KNAPWEED
HAS LITTLE
VALUE AS FORAGE FOR CATTLE AND
LIMITED SEASONAL VALUE FOR BIG GAME.
INFESTATIONS INCREASE PRODUCTION
COSTS FOR RANCHERS, DECREASE PLANT
DIVERSITY AND WILDLIFE HABITAT,
INCREASE SOIL EROSION RATES AND POSE
WILDFIRE HAZARDS.
HOARY CRESS
IS INVADING
RANGELANDS THROUGHOUT NORTH AMERICA.
IT IS A HIGHLY COMPETITIVE WEED ONCE IT
BECOMES ESTABLISHED. HOARY CRESS
SPREADS PRIMARILY BY EXTREMELY
PERSISTENT ROOTS AND WILL EVENTUALLY
ELIMINATE DESIRABLE VEGETATION AND
BECOME A MONOCULTURE.
HOUNDSTONGUE IS A VERY STRONG
COMPETITOR OF DESIRABLE FORAGE AND IS
POISONOUS. IT CONTAINS PYRROLIZIDINE
ALKALOIDS THAT STOP THE REPRODUCTION
OF LIVER CELLS. SHEEP ARE LESS SUSCEPTIBLE
THAN CATTLE OR HORSES. IT CAN ALSO
CAUSE DERMATITIS IN HUMANS.
Jointed
Oatgrass
Jointed oat grass
is a troublesome
winter annual in
winter wheatfallow
production areas.
It can hybridize
with winter
wheat and reduce
wheat crop
yields.
LEAFY SPURGE IS TOXIC TO SOME
ANIMALS AND REDUCES THE LIVESTOCK
CARRYING CAPACITY OF PASTURE AND
RANGELAND BY 20 TO 50%, CAUSING AN
ESTIMATED $35-45 MILLION LOSS PER YEAR
IN US BEEF AND HAY PRODUCTION IN
ADDITION TO THE MILLIONS OF DOLLARS
SPENT FOR CONTROL.
MUSK THISTLE IS SIMILAR TO
CANADA THISTLE (CIRSIUM ARVENSE[L.]
SCOP.) AND BULL THISTLE (CIRSIUM
VULGARE [SAVI.]), BOTH OF WHICH ARE ALSO
NON-NATIVE. THERE IS SOME EVIDENCE OF
HYBRIDIZATION OCCURRING BETWEEN MUSK
THISTLE AND NON-NATIVE PLUMELESS
THISTLE (CARDUUS ACANTHOIDES [L.]). MUSK
THISTLE IS DISTINGUISHED FROM OTHER
THISTLES BY THE USUALLY LARGE DISKSHAPED FLOWERS.
Oxeye
Daisy
The oxeye daisy is short-lived
perennial originally brought here
from Europe. The dainty flowers
have escaped cultivation and
now crowd out other plants on
many rangelands. A vigorous
daisy can produce 26,000 seeds
per plant, while smaller
specimens produce 1,300 to
4,000 seeds per plant. Tests
have shown that 82% of the
buried seeds remained viable
after six years, and 1% were still
viable after 39 years. Oxeye
daisy requires cold winters to
initiate blooming. The plant also
reproduces vegetatively with
spreading rootstalks. Daisies are
resistant to many herbicides.

Perennial pepperweed
(Lepidium latifolium) is an
extremely invasive perennial forb
introduced from Europe and Asia
in 1900 as a containment in
sugar beet seed. Pepperweed
reproduces both by seed and
vegetatively by roots and shoots.
Root fragments as small as 0.5
inch can grow into new plants. A
serious threat, pepperweed
alters ecosystems by acting as
a “salt pump” absorbing salts
from deep in the soil. The plant
then excretes the salt through
the leaves and deposits it on the
surface soil. Since most desirable
plants do not tolerate plant
composition and diversity high
saline concentrated soils, the
entire of the area changes.
PLUMELESS THISTLE
INVADES PASTURES, MEADOWS,
AND FIELDS CROWDING OUT
DESIRABLE FORAGE PLANTS.
LIVESTOCK WILL NOT GRAZE IN
AREAS HEAVILY INFESTED WITH
PLUMELESS THISTLE
QUACKGRASS,
AN AGGRESSIVE PERENNIAL WEED, IT
HAS A DEEPER ROOT SYSTEM THAN
CRABGRASS AND REEMERGES EVERY
YEAR. IT REPRODUCES FROM SEEDS AND
UNDERGROUND RHIZOMES. THE
RHIZOMES ARE VERY AGGRESSIVE AND
MAKE CONTROLLING THIS PLANT VERY
DIFFICULT. QUACKGRASS HAS AURICLES
THAT CLASP AT THE STEM WITH HAIRY
LEAVES. THE BEST WAY TO CONTROL
THIS PLANT IS WITH A NON-SELECTIVE
HERBICIDE LIKE GLYPHOSATE.
RUSSIAN KNAPWEED
IT IS AN AGGRESSIVE INVADER OF
PASTURES, NON-CROP AREAS,
GRAIN FIELDS AND OTHER
CULTIVATED FIELDS. IN
ADDITION, THE PLANT IS
POISONOUS TO HORSES, CAUSING
CHEWING DISEASE (EQUINE
NIGROPALLIDAL
ENCEPHALOMALACIA).
LIVESTOCK MAY AVOID THIS
SPECIES.
THE
RUSSIAN OLIVE,
WITH ITS TENDENCY TO SPREAD QUICKLY, IS A
MENACE TO RIPARIAN WOODLANDS,
THREATENING STRONG, NATIVE SPECIES LIKE
COTTONWOOD AND WILLOW TREES. THEY ARE
RESPONSIBLE FOR OUT COMPETING A LOT OF
NATIVE VEGETATION, INTERFERING WITH
NATURAL PLANT SUCCESSION AND NUTRIENT
CYCLING AND CHOKING IRRIGATION CANALS
AND MARSHLANDS IN THE WESTERN UNITED
STATES. THIS DISPLACEMENT OF NATIVE PLANT
SPECIES AND CRITICAL WILDLIFE HABITATS HAS
UNDOUBTEDLY AFFECTED NATIVE BIRDS AND
OTHER SPECIES. THE HEAVY, DENSE SHADE OF
THE RUSSIAN OLIVE IS ALSO RESPONSIBLE FOR
BLOCKING OUT SUNLIGHT NEEDED FOR OTHER
TREES AND PLANTS IN FIELDS, OPEN
WOODLANDS AND FOREST EDGES. THE RUSSIAN
OLIVE HAS BEEN CATEGORIZED AS A NOXIOUS
WEED IN NEW MEXICO AND UTAH. THERE IS A
SERIOUS CONCERN THAT SHOULD THE RUSSIAN
OLIVE CONTINUE TO ESTABLISH ITSELF, IT WILL
BECOME THE DOMINANT WOODY PLANT ALONG
COLORADO’S RIVERS, WHERE IT IS ALREADY
TAKING OVER HUNDREDS OF THOUSANDS OF
ACRES OF COTTONWOOD AND WILLOW
WOODLANDS. SOME CITIES ARE ALREADY
TAKING STEPS TO REMOVE THE RUSSIAN OLIVE.
Salt cedar is a shrub or tree native to
the Mediterranean, China and
Central Asia. This plant is found
infesting waterways throughout the
west. These plants contain salt that
they deposit onto the soil through
their leaves. Other riparian species
are unable to survive the salty
conditions and Salt cedar can then
become the only plant growing in an
area. Some reports show that one acre
of Salt cedar can use 7.7 acre feet of
water a year (2.8 million gallons).
Although this plant has been sold as
an ornamental in the past, it is no
longer allowed to be sold in
Colorado.
Scotch Thistle
Scotch thistle is a problem in rangeland.
Infestations of Scotch thistle reduce forage
production and virtually prohibit land
utilization for livestock. Dense stands of the
large, spiny plants exclude animals from
grazing and access to water.
How would I identify it?
Scotch thistle is a branched, biennial
or annual with a broadly winged stem
that can grow up to 8 feet or more in
height and 6 feet in width.
SPOTTED AND RUSSIAN KNAPWEED
ARE TWO MEMBERS OF THE SOUTHWEST'S “DIRTY
DOZEN ”INVASIVE WEED SPECIES. SPOTTED KNAPWEED
(CENTAURIA MACULOSA LAM.) IS A SHORT-LIVED,
NONCREEPING PERENNIAL THAT REPRODUCES FROM
SEED AND FORMS A NEW SHOOT EACH YEAR FROM A
TAPROOT.
SPOTTED KNAPWEED CAN BE CONTROLLED WITH
HERBICIDES; HOWEVER, THE WEEDS WILL REINVADE IF
CULTURAL TECHNIQUES ARE NOT INTEGRATED INTO
THE MANAGEMENT PLAN.
YELLOW TOADFLAX,
BUTTER AND EGGS, WILD
SNAPDRAGON, COMMON
TOADFLAX, RAMSTED,
FLAXWEED, JACOB'S
LADDER
The San Luis Valley Weed Management
Association
partners with the following
in our mission
“to promote awareness and
management of
noxious weeds through local and
regional initiatives in the SLV area.”
National Park Service and the Great Sand Dunes
San Luis Central Railroad Company
Rio Grande National Forest
USBR
CDOT
Colorado State Land Board
Mineral County
San Luis & Rio Grande Railroad
USFWS
CDOW
Colorado State Parks
San Luis Water Conservancy District
Denver and Rio Grande Historical Foundation
Center Conservation District
Colorado State Forest Service
Conejos Conservation District
Costilla Conservation District
Mosca-Hooper Conservation District
Rio Grande County Conservation District
Bowen Drain Ditch Company
Monte Vista Canal
Rio Grande & Piedra
Rio Grande San Luis Ditch
Lariat Ditch
Rio Grande Canal
Farmers Union Canal
San Luis Valley Noxious
Weed Management
Association