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Common Grasses and Weeds

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- Blue Gramma

- Larkspur



-Western Wheatgrass



Blue Gramma   

Blue Gramma is a long lived, warm season, C4 perennial grass native to North America. It is most commonly found from Alberta east to Manitoba and south across the Rocky Mountains, Great Plains, and Midwest states to Mexico. Blue Gramma accounts for most of the net primary productivity in the shortgrass prairie of the central and southern Great Plains.


     -         Blue Gramma is the state grass of Colorado and New Mexico.

-         Turns purple with first frost and bleaches to white during winter.

-         Fine textured grass spreads by underground rhizomes

-         Can be used as turf grass or in rock gardens


-         Plant height at maturity ranges from 15-30 cm.

-         Roots generally extend 30-46 cm from the edge of the plant and 0.9 to 1.8 m deep.

-         Blue Gramma is green to grayish in appearance.

-         Blooms appear in September resembling tiny combs

-         This plant likes dry conditions.


    For cattle producers, larkspur causes more monetary loss than any other poisonous weed. All species of the weed, including the cultivated garden varieties, are poisonous. In general, cattle are the only type of livestock that die from larkspur poisoning. Horses and sheep rarely eat enough of the weed to harm themselves.

 When and where is it found?

            Larkspur begins growing in the early spring, often before other forage, making it the first green feed available. Generally, larkspur is grouped into 2 types- low larkspur and tall larkspur.

            Low larkspur grows on the plains and in the foothills of Colorado. It enjoys 4,000 to 10,000 foot altitudes.

            Tall larkspur grows at higher altitudes Ė usually between 8,000 and 11,000 feet. They often grow in deep soils where moisture is plentiful.

 What does it look like?

            Low larkspur has spurred blue (purple) flowers that grow on the top third of a single, branchless stem. The plants often reach 2 feet tall. Low larkspur dies down after it flowers in early June, but the top of the plant remains alive until itís killed by frost. All parts of the plant are poisonous while the plant is alive.

            Tall larkspur grows spurred blue (purple) flowers on top of their stalk, similar to that of garden delphinium. The plant can reach 1 to 5 feet tall. Leaves grow up the length of the stalks on alternating sides. The wee has broad leaves that are divided into deep lobes. In contrast, wild geranium, which is often mistaken for tall larkspur, has shallow leaf lobes.

 How does it affect livestock?

            All parts of the larkspur plant are poisonous, but new growth and the seeds contain the highest concentrations of toxic substances. Larkspur is highly palatable to cattle, especially after the plant flowers. For unexplained reasons, rain, cold fog, or snow showers may lead to greatly increased consumption of the plant. Acute larkspur poisoning in a range cow can resemble grass tetany and milk fever (hypocalcaemia).

            Sudden death in cattle is often the first indication of larkspur poisoning. Cattle frequently die within 3 to 4 hours of consuming a lethal dose (20-25 pounds for an adult) of larkspur. Poisoned cattle initially show uneasiness increased excitability, and muscle weakness that causes the animal to knell before collapsing. An animalís frequent attempts to stand are uncoordinated, and result in rapid exhaustion. Muscle twitching, abdominal pain, vomiting, and bloat are common. Similar signs of poisoning occur in horses, sheep, and goats that have eaten large amounts of larkspur, except that vomiting is uncommon and fewer deaths are likely. Sheep can withstand 4 times more larkspur than cattle. 

  What are the signs of an infected animal?




        Increased Salivation

        Muscle Quivers


        Falling with head downhill


  What if my animal has been poisoned?

            Often, poisoned animals arenít found until they are dead. If you do find an animal you suspect has been poisoned, keep the animal quiet, turn its head uphill, and puncture if badly bloated, but donít bleed. Call your vet. There is no proven treatment for larkspur poisoning.

            If an animal is found soon after ingesting large amounts of the plant, there may be some effective drug treatments that can be administered.  These treatments may reverse some of the signs of poisoning, but their effects on larkspurís lethal effects are unproven. However, the stress and excitement of treatment may outweigh and beneficial therapeutic effects. If less than a lethal dose of larkspur is consumed, an animal will likely recover despite the treatments, unless they experience severe bloat.

  How can I reduce my losses?

            Since tall larkspur isnít palatable in its early growth stage, grazing infested areas before the plant flowers may help control poisoning. However, early grazing isnít an option for low larkspur because it is highly palatable in its early growth stages. Using sheep to graze or trample larkspur patches ahead of cattle grazing may also reduce cattle losses.

            Providing adequate calcium, phosphorous, and mineralized salts for cattle has been recommended as a preventive measure for larkspur poisoning. Cattle may be deficient in minerals in late winter and early spring and crave plants like larkspur that are high in calcium.

            Although it is possible to control larkspurs with herbicides, it isnít economically to use chemicals on a large scale. However; spraying larkspur hotspots can be effective in reducing cattle losses.



    Locoweed is one of the most common and costly causes of livestock poisoning in the Western United States. The weed is toxic to cattle, sheep, horses, elk, deer, and antelope.

 What else is it called?

          The name locoweed is derived from Spanish word loco (meaning crazy) which is how the abnormal behavior of poisoned animals is often described. The weed is also known as silky crazyweed, milk vetch, and Lambert crazyweed.

 When and where is it found?

          Locoweeds can grow in all parts of Colorado.  The plants are indigenous to the Rocky Mountain area and prefer to grow in the open prairie, foothills, and often in well-drained soils of decomposing granite. They are one of the first spring forages to appear-usually beginning in mid April Ė and they grow throughout the summer. Locoweeds are relatively palatable during spring and fall when they are green and associated forage is dry and dormant. All parts of the weeds are always poisonous, even during the winter months when they are mature and dry. Locoweeds are prolific seed producers. Their seeds may remain viable in the soil for 50 years or more.

 What does it look like?

*       Locoweed is a perennial that grows in clumps.

*       Mature plants range in height from 6 to 12 inches.

*       Leaves are compound, covered with fine hairs, and grow close to the ground. Each stem includes numerous leaves.

*       Leafless, flowered stalks emerge from the center of the plant, forming a spike like cluster.

*       Flowers are pea-like and may be blue, pink, purple, yellow, or white.

*       The plant produces kidney-shaped seeds in a hairy, leather-like pod.

 How does it affect livestock?

            Livestock are poisoned by ingesting any part of the locoweed. Swainsonine, the toxin found in all parts of the plant, affects the central nervous system and accumulates in the cells of the brain and other organs. The poison is secreted in the milk of infected lactating livestock, therefore affecting suckling animals too. In addition, Swainsonine readily crosses the placenta, often resulting in fetal death, abortion, congenital defects, and weak newborns.

            Depending on the duration of locoweed consumption, the affected cells in a poisoned animal can be permanently damaged. If an animalís exposure to locoweed is short, the animal often recovers with few noticeable side effects, if any. However, the neurological signs of poisoning may unpredictably recur. Horses often show more sever neurological effects of locoweed poisoning than cattle and sheep. The unpredictable behavior makes the animals dangerous to work around or ride. With chronic locoweed poisoning, livestock become emaciated and lose the ability to find and utilize feed.

            Livestock generally avoid eating locoweed unless feed is scarce. However, the plant has a relatively high nutrient value, and once animals develop a taste for the plant, they will graze it preferentially. Locoweeds are palatable and of similar nutrient value to alfalfa, which helps explain why animals eat them even when normal forages are present. Animals that selectively graze locoweed will in turn teach their offspring and other animals to eat it.

 What are the signs of an infected animal?

            Poisoned animals may have all, some, or none of these symptoms depending on the severity of the poisoning. Symptoms usually appear 2 to 3 weeks after continuous grazing on the plant.  

*       Depression, lethargy, weakness

*       Decreased growth rate

*       Dully, dry hair coat

*       Eyes dull and staring

*       Irregular gait or some loss of muscle control

*       Extreme nervousness of aggression if stressed

*       Withdrawal from other animals

*       Inability to eat, drink, or absorb essential vitamins and minerals

*       Increased susceptibility to infectious diseases

*       Decreased fertility

*       Abortions, fetal death, birth defects

*       Congestive heart failure at high elevations

*       Death

  What if my animal has been poisoned?

            If you suspect an animal has been poisoned, immediately remove your livestock from the pasture and inspect the pasture for the presence of the weed. There is no effective treatment for locoweed poisoning. A serum test can be done to detect the toxin in an animal, but the test must be performed within 24 hours of ingestion. Locoweed poisoning can also be detected post mortem. Poisoned horses are often considered unrideable because of their unpredictable neurological symptoms.

            If calves are affected, it is recommended that vaccinations be delayed, or that locoed calves be revaccinated at least 30 days following removal from locoweed infested areas. This will help ensure that calves receive adequate protection against diseases as IBR and BVD.

 How can I reduce my losses?

            Locoweeds are relatively palatable during spring and fall when they are green and associated forage is dry or dormant. Chemical eradication of locoweed from all areas where livestock graze is neither economically nor environmentally feasible. Therefore, it is necessary to incorporate management practices that will allow livestock to continue to utilize locoweed infested ranges with minimal economic impact.  

1.      Restrict access to locoweed during critical periods when the plant is more palatable than associated forages.

2.      Livestock should not be turned onto spring ranges until desirable forages have made sufficient growth to support grazing.

3.      Hungry animals should never be turned onto range or pastures infested with poisonous plants. Livestock graze less selectively when hungry.

4.      Maintain conservative stocking rates to avoid forcing animals to consume locoweed when desirable forage becomes limited.

5.      Remove animals that begin eating locoweed to prevent repeat intoxication and to keep them from influencing others to start eating the plant.


            In the Western United States, all livestock are susceptible to lupine poisoning, but sheep are primarily affected. Losses may be especially heavy when hungry sheep are trailed through lupine ranges in late summer.

 When and where is it found?

            Lupine grows on sagebrush ranges and on grassy slopes. It is found in areas up to 11,000 feet high.  The poisonous species in Colorado are perennials. They emerge early in the spring, flower in June, and lose seeds in July or August. During years with a wet spring, lupine populations explode and may be especially troublesome.

 What does it look like?

            Lupine are bushy plants that grow in clumps. The weed reach heights of 1-2 feet tall. Their leaves are palm-like and composed of several leaflets, which radiate from a central point. The pods are usually hairy and the flowers grow in clusters on the stalk. Although blue is the most common color, flowers may also be white, pink, yellow, or blue and white. 

 How does it affect livestock?

            Lupine is dangerous from the time it starts to grow in the spring until it dries up in the fall. Younger plants are more toxic than older plants; however, plants in the seed stage in late summer are especially dangerous because of the high toxin content of the seeds. Lupine is also more palatable than the dried pasture grasses in the late summer.

            The amount of lupine that will kill an animal varies with the lupine species and the stage of plant growth. A sheep that is getting good forage may not be affected by occasionally eating a small amount of lupine ( about 1/8 to ľ lb.), but a sheep is usually poisoned if it eats 1/8 to ľ lb. of lupine daily for 3 to 4 days.

            Cattle may be poisoned by eating 1 to 1 Ĺ lbs. of lupine without other forage. Smaller amounts are poisonous if cattle eat the weed daily for 3 to 7 days. If cows consume the plant between days 40 and 70 of gestation, their calves will often suffer from crooked calf disease. These calves are born with cleft palates, crooked legs and distorted /malformed spines. Epidemic outbreaks of such birth defects can have high morbidity resulting in enormous animal and economic losses.  

 What are the Symptoms of an infected animal?


        Excessive salivation, frothing at the mouth



        Difficulty Breathing

        Leg muscle twitches, loss of all muscular control




What if my animal has been poisoned?

            There is no antidote for lupine poisoning. Allow affected livestock to rest quietly, especially if they are unfamiliar with human contact. Handling, trailering, or other stress on animals after they have been grazing lupine will make the signs worse and can increase losses.  

How can I reduce my losses?

            Losses can be reduced by keeping hungry animals away from lupine patches in their early growth stage and in late summer when the plant is in the highly toxic seed stage. Animals should always be kept away from dense plant stands. Supplemental feeding is beneficial, especially when animals are trailed through lupine ranges.

            Do not allow hungry animals to have access to lupine, particularly when itís the seed stage, if other forage is not available.  If lupines are prevalent in the pasture, become familiar with the particular species present, since toxicities vary. Do not handle, process, or ship animals that are heavily grazing lupine since this type of stress will increase the number of animals that will become sick and/or die. Livestock can graze lupine without incident as long as excessive ingestion is avoided and animals are not handled or trailered while on lupine pastures ( and if the animals are not pregnant) In cattle, to avoid birth defects, do not allow grazing between days 40 and 70 of gestation.

            In addition, since the toxins in lupine remain after the plants have dried, hay containing the weed is unsafe for livestock.


Western Wheatgrass

Crested Wheat Grass

   Western wheatgrass is a native grass found in most areas of the United States. Its major range is the northern and central Great Plains region, which includes Colorado.


-         Is excellent forage for cattle, horses, and sheep.

-         Plant is readily eaten during the early growth stage.

-         Makes quality, high-protein hay when cut during the late-bloom stage.

-         Provides good winter grazing.

-         Commonly used to seed roadside ditches and to reclaim other disturbed areas.

-         Moderate grazing stimulates production of new sprouts and increases its vigor.

-         Because it sprouts from rhizomes, it can recover quickly from prolonged drought.

-         It is often the first species to fill areas that have lost vegetation due to dry spells.


-         Perennial that grows from 1 to 3 feet tall.

-         Sometimes called bluestem wheatgrass because of its bluish-colored stems and leaves.

-         The leaves Grows from 12 to 35 inches high

-         Leaves growgrow off the stem at a 45 degree angle. They are stiff, flat, and mostly smooth with a rough, ribbed upper surface.

     -         The seed head is a slender spike.


-         Grows well in a variety of soils, especially clay.

-         Is a cool season species that starts growing in May and June when the temperatures reach approximately 54 degrees Fahrenheit.

-         The plant goes dormant in mid-summer.  It can grow again in the fall if there is adequate soil moisture.

-         Reproduces both sexually, with seeds, and asexually with underground stems called rhizomes. Single grass stems arise from the spreading rhizomes.

-         Its long rhizomes give it an erect, but creeping growth pattern.

-         Underground its highly branched roots penetrate the soil to a depth of seven feet.


The scientific name for the western wheatgrass is Agropyron smithi. It comes from the Greek words "agrios" meaning wild and "pyros" meaning wheat. Smithii refers to the botanist, Gerald Smith, who discovered the species.


Photo of Pascopyrum smithii (Rydb.) A. LŲve