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Recognizing and Managing Common Pasture Weeds

Pastures are the backbone of many livestock operations, providing essential forage throughout the grazing season. However, maintaining a productive and healthy pasture means keeping weeds in check, overgrazing and drought are some conditions that can weaken a stand leading to weed encroachment. Some species not only compete with desirable forages for nutrients, water, and light but can also be harmful to livestock or reduce pasture usability.

This article highlights some of the most common and problematic pasture weeds observed across the Midwest and offers practical identification tips and management considerations. 

Common and Problematic Pasture Weeds: 

Musk Thistle (Carduus nutans)

  • Key traits: A biennial with large, spiny leaves without hairs, silver/white leaf margins, and a distinctive bowl shaped, nodding purple flower head with sharp bracts on the backside of the flower. Larger flower in comparison to bull thistle.
  • Concerns: Reduces grazing area due to its prickly nature and competes with the forage stand.
  • Management: Mow after bolting but before seed set, spot-spray with herbicides in rosette stage fall of the first year or early spring of the second year, and maintain competitive forage stands.
  • More information: ISU Encyclopedia Article - Musk Thistle and ISU IPM – Weed ID: Musk Thistle
Musk thistle rosette
Figure 1a: Musk thistle rosette. Image courtesy of Meaghan Anderson.
Musk thistle flower
Figure 1b: Musk thistle flower. Image courtesy of Meaghan Anderson.

 

 

Bull Thistle (Cirsium vulgare)

  • Key traits: Biennial; deeply lobed leaves with stiff spines and coarse hairs on the upper side of the leaves and soft white hairs on the lower side of the leaves, with vase-shaped purple flower.
  • Concerns: Reduces grazing area due to its prickly nature, making it unpalatable.
  • Management: Mow after bolting but before seed set, spot-spray with herbicides in rosette stage fall of the first year or early spring of the second year, and maintain competitive forage stands.
  • More information: ISU Encyclopedia Article - Bull Thistle and ISU IPM  - Weed ID: Bull Thistle
Bull thistle leaves
Figure 2a: Bull thistle leaves. Image courtesy of Meaghan Anderson.
Bull thistle rosette
Figure 2b: Bull thistle rosette. Image courtesy of Meaghan Anderson.

 

 

Canada Thistle (Cirsium arvense)

  • Key traits: Perennial; smaller (~1/2”) white to lavender flowers and very extensive, creeping, and deep root system.  Leaves are irregularly lobed; spininess is highly variable. Smaller than the biennial thistles. Generally found in patches due to vegetatively propagating through rhizomes.
  • Concerns: Extremely difficult to manage due to its extensive root system, and unpalatable due to its spines.
  • Management: Repeated mowing throughout the summer and targeted herbicide applications during the fall or in the bud to early bloom stage. Improving forage density helps suppress regrowth.
  • More information: ISU Encyclopedia Article - Canada Thistle, ISU IPM – Weed ID: Canada Thistle, and ICM News - Spring Control Of Canada Thistle – Now Is The Time!
Canada thistle roots
Figure 3a: Canada thistle roots. Image courtesy of Meaghan Anderson.
Figure 3b: Canada thistle plants starting to bud. Image courtesy of Meaghan Anderson.
Bull thistle flower and Canada thistle flower.
Figure 4: Photo of bull thistle flower (left) and Canada thistle flower (right). Image courtesy of Meaghan Anderson.

Wild Carrot (Daucus carota)

  • Key traits: Biennial; finely divided leaves, hairy stem, and white, flat-topped flower clusters often with a small purple flower in the center ('Queen Anne’s lace').
  • Concerns: Competes with desirable species, especially in overgrazed pastures.
  • Management: Treat with herbicides in fall or early spring during rosette stage, mow or cut after bolting but before flowering.
  • More information: ISU Encyclopedia Article - Wild Carrot and ISU IPM – Weed ID: Wild Carrot
Wild carrot rosette
Figure 5a: Wild Carrot's rosette. Image courtesy of Bob Hartzler.
Wild carrot flower
Figure 5b: Wild Carrot's flower cluster. Image courtesy of Bob Hartzler.

Wild Parsnip (Pastinaca sativa)

  • Key traits: Biennial; yellow umbel flower clusters, deeply lobed leaves, and hairless, ridged stem.
  • Concerns: Sap causes severe skin irritation and blistering upon exposure to sunlight (phytophotodermatitis).
  • Management: Wear protective clothing when handling. Treat with herbicides in fall or early spring during rosette stage, mow or cut after bolting but before flowering.
  • More information: ISU Encyclopedia - Wild Parsnip
Wild parsnip rosette
Figure 6a: Wild parsnip's rosette (right). Image courtesy of Bob Hartzler (right).
Wild parsnip flower
Figure 6b: Wild parsnip's flowering cluster. Image courtesy of Meaghan Anderson.

Poison Hemlock (Conium maculatum)

  • Key traits: Tall biennial; fern-like leaves and white umbrella-shaped flowers; purple-spotted, hairless stems. Can be mistaken for wild parsnip and wild carrot.
  • Concerns: Extremely toxic to livestock and humans if ingested.
  • Management: Wear gloves when handling. Treat with herbicides in fall or early spring during rosette stage, mow or cut after bolting but before flowering
  • More information: ISU Encyclopedia Article - Poison Hemlock and ISU IPM – Weed ID: Poison Hemlock
Posion hemlock stem
Figure 7a: Poison hemlock has purple spots on its stem. Image courtesy of Meaghan Anderson.
poison hemlock flowers
Figure 7b: Poison hemlock flowering, note the white flower clusters similar to wild carrot. Image courtesy of Meaghan Anderson.

Common Burdock (Arctium minus)

  • Key traits: A biennial with large rough egg to heart-shaped basal leaves; produces burr-like seed heads that stick to animals and clothing.
  • Concerns: Burrs can damage fleece or hide and reduce pasture appeal.
  • Management: Treat with herbicides in fall or early spring during rosette stage, mow or cut after bolting but before flowering
  • herbicide in rosette stage can be effective.
  • More information: ISU Encyclopedia Article - Common Burdock and ISU IPM – Weed ID: Common Burdock
Common burdock
Figure 8a: Common burdock rosette. Image courtesy of Bob Hartzler.
Common burdock flower
Figure 8b: Common burdock burs developing. Image courtesy of Bob Hartzler.

Common Cocklebur (Xanthium strumarium L.)

  • Ket Traits: Annual with triangular leaves with irregular margins, and rough stems with dark specks/spots.
  • Concerns: Toxic particularly during the seedling stage but decreases as the plant gets older.
  • Management: Remove prior to seed set.  Post-emergent broadleaf herbicides can control cocklebur seedlings.
  • More information: ISU Encyclopedia Article - Common Cocklebur
Cocklebur seeding
Figure 9: Seedling of common cocklebur. Image courtesy of Meaghan Anderson.

Multiflora Rose (Rosa multiflora)

Multifloral rose leaf shop with fringed stipule at the base
Figure 10a: Multifloral rose leaf shape with fringed stipule at the base. Images courtesy of Meaghan Anderson.
Figure 10b: Multifloral rose flowering shrub. Image courtesy of Bob Hartzler.

 

 

Horsenettle (Solanum carolinense)

  • Key traits: Perennial with spiny stems and leaves, leaves are egg shaped with wavy margins and a few shallow lobes, white to pale violet star-shaped flowers, and yellow berry-like fruits.
  • Concerns: Contains toxic alkaloids harmful to livestock if ingested in quantity. The spiny stems also deter grazing, leading to pasture underuse.
  • Management: Difficult to control due to deep, spreading roots. Mow before seed set and apply systemic herbicides. Maintain dense forage to minimize spread.
  • More information: ISU Encyclopedia Article - Horsenettle and ISU IPM – Weed ID: Hersenettle
Horsenettle plant
Figure 11: Two horsenettle plants growing in a pot (left) and closer view of the leaves and stems, note the spines coming out of the prominent veins on the underside of the leaf (right). The yellowing (chlorosis) of the leaves is due to restrictions of being in a pot, typically leaves are more green in color. Images courtesy of Shelby Gruss.

 

Yellow Foxtail (Setaria pumila)

  • Key traits: Annual grass with flat, narrow leaves with hairy ligules, sparse long hairs at the base of the leaf, and a distinctive cylindrical seedhead (“foxtail”) with yellow awns that emerges in late summer.
  • Concerns: Reduces pasture quality by competing with more desirable forages. The bristly seedheads can cause mouth irritation in grazing animals.
  • Management: Mow before seedheads form to reduce seed production, but consistent mowing is necessary as actively growing foxtail will regenerate seed head within two weeks of mowing. Although it can form seed heads very low to the ground skirting the mower deck. Maintain healthy forage density to outcompete seedlings. Pre-emergent herbicides may be effective in established pastures but if populations are high, pastures often require renovation.
  • More information: ISU Encyclopedia Article - Yellow Foxtail
yellow foxtail hairs by leaf collar
Figure 12a: Yellow foxtail a close up on the leaf collar, note the hairs at the base of the leaf. Image courtesy of Meaghan Anderson. 
yellow foxtail seeded
Figure 12b: Yellow foxtail with seed heads developing. Image courtesy Meaghan Anderson. 

Chicory (Cichorium intybus)

  • Key traits: Perennial forb with bright blue flowers, deeply-lobed basal leaves resembling dandelion leaves, and a thick taproot.
  • Concerns: Its bitter taste limits livestock preference once mature but will be grazed early spring and following a frost.
  • Management: Targeted herbicide applications before flowering. Maintain good forage cover to reduce establishment. Regular mowing can help reduce seed production but will unlikely kill the plant.
  • There are forage chicory varieties. These are typically higher yielding, more palatable, and nutritional value and mineral content similar to alfalfa.
Chicory flowers and plant
Figure 13: Chicory flowers, note the purple/blue flower heads, the pink flower head is red clover (left) and chicory flowering in a pasture (right). Image courtesy of Shelby Gruss (left) and Rachel Kennedy (right). 

 

 

 

Management Dependent on Your Stand

Weed control strategies should be tailored to the type of forage stand present. In predominantly grass-based pastures, selective broadleaf herbicides can be used effectively without harming the forage species. However, in mixed grass-legume stands (such as those containing clover), herbicide options are much more limited since most broadleaf herbicides will also damage desirable legumes. In these cases, mechanical control methods like mowing, hand-pulling, or grazing management become especially important. Although starting with and maintaining dense, vigorous forage growth through proper fertilization, rotational grazing, and overseeding is one of the best strategies in control weeds. As many weeds are opportunistic and become established in weaker areas of the stand.

Final Thoughts

Regular pasture monitoring, maintaining dense forage cover, and addressing weed issues early are key to minimizing long-term impacts. Consult with your local extension agronomist for tailored recommendations and approved herbicide options. When selecting herbicides, check the labels for crop rotation restrictions, pre-harvest intervals/grazing restrictions. One source you can check is cdms.net/label-database. More information of herbicide options can be found in: WC 94

Additional tools for weed identification and more information on toxic weeds: 

 

Authored by:
Shelby Gruss
Shelby Gruss
  • Assistant Professor
  • Forage Extension Specialist
Dr. Gruss earned a Ph.D. in Plant Breeding and Genetics from Purdue University.
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