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Managing problem plants in silvopasture systems

Quick facts

  • Problem weeds and plants can appear in any pasture.
  • Most problem plants can be controlled and managed easily if identified early, managed and monitored.
  •  The Minnesota Department of Agriculture enforces the Minnesota Noxious Weed Law.

Controlling noxious weeds, invasive species, poisonous and woody plants

Silvopasture systems are managed rotational grazing practices that benefit forages and grasses, trees and livestock. Vegetation in any landscape does not stay the same, it is constantly changing.

Problem weeds such as noxious, invasive species, poisonous and woody plants can appear in any pasture. Most problem plants can be controlled and managed easily if identified early, managed and monitored.

Plant identification and life cycles

Knowing the difference between good forbs or grasses and noxious or invasive weeds in your pasture is extremely important. When undesirable weeds or plants are identified, knowing the plant life cycle is valuable in selecting appropriate methods of control.

Annual

  • Live one year, grow and seed.
  • Control: Mow, pull, herbicide.

Biennial

  • Live two years, vegetative growth the first year then seeds the second year.
  • Control: Mow, pull, herbicide.

Perennial

  • Lives more than 2 years and may have rhizomes.
  • Control: Pull at young stage, systemic herbicide.

Minnesota noxious weeds

Noxious weeds are annual, biennial, or perennial plants that the commissioner of agriculture designates as having the potential to be or are known to be detrimental to human or animal health, the environment, public roads, crops, livestock or other property. The Minnesota Department of Agriculture is the lead agency in enforcing the Minnesota Noxious Weed Law.

Noxious weed designations

The Eradicate and Control lists change annually. Check the MDA website in January. Plants on these lists should be reported to the Minnesota Department of Agriculture.

  • Prohibited Eradicate: Must eradicate by killing above and below-ground parts of the plant.
  • Prohibited Control: Must be controlled, prevent maturation and spread of propagating plants.
  • Restricted: Not to be sold, planted or transported.
  • Specially Regulated: Specific regulations on distributing, controlling or eradicating.

Noxious weed pest hotlines

Invasive species

Invasive species are species that are not native to Minnesota and cause economic or environmental harm or harm to human health.

The Minnesota Department of Natural Resources lists 52 terrestrial invasive plants in Minnesota.

Plants poisonous to livestock

Poisonous plants contain toxic compounds that can injure animals. Some contain compounds that can kill, even in small doses. Others contain substances that reduce performance, such as weight loss, weakness, rapid pulse and unthriftiness.

See Plants poisonous to livestock and Plants poisonous or harmful to horses.

Nitrate poisoning

Nitrates accumulate in certain plants (sorghum-sudangrass, corn or corn silage, redroot pigweed, common lamb's-quarters) when drought or frost stressed or when they have been fertilized with nitrogen.

Top cattle poisonous plants

  • Gallotannins in oak species (leaves and green acorns)
  • Sorghum and sudangrass
  • Chokecherry
  • Eastern black, hairy and climbing (bittersweet) nightshades
  • Cocklebur
  • Water hemlock
  • Poison hemlock 

Grazing tips to prevent poisoning

  • Avoid overgrazing pastures.
  • Avoid turning hungry animals into new pastures.
  • Learn to identify poisonous plants.
  • Fence off areas in pastures where poisonous plants occur.
  • Control or manage plants to avoid poisoning problems.
  • Follow herbicide grazing restrictions.
  • Rotate pastures to prevent overgrazing.
  • Supply adequate supplies of clean, fresh water for livestock.
  • Consult your veterinarian to correctly identify a suspected poisoning from plants, in order to prevent it from happening in the future.

Woody plant control

Consider these methods to control woody trees and shrubs. Type of control depends on the age, the diameter of the stem, and distribution.

  • Pulling small and fibrous root systems, not tap root or rhizomes.
  • Broadcast spray of foliage.
  • Basal treatment (bark).
  • Cut stump – best for older and larger trees.
    • Most woody stumps need to be treated with a labeled brush herbicide.
    • Use herbicides labeled for woody plants.
    • Look for Triclopyr as an active ingredient.
  • Many coniferous trees (spruce and pine) do not need stump treatment.

See Controlling unwanted trees and shrubs.

Gary Wyatt, Extension forestry educator

Reviewed in 2020

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