Managing Weeds in Kentucky Horse Pastures

What grows in your pasture? Ideally, abundant forage that is nutritious to horses. However, a perusal of most Kentucky horse pastures will uncover 20 plant species, many of which are weeds. The abundance of weedy species depends greatly on pasture management: Overgrazing of pasture grasses and soil compaction are primary causes of weed occurrence.

A high-quality, nearly weed-free forage is ideal if pasture comprises a significant portion of a horse's diet. Conversely, a pasture maintained as a drylot will contain many weeds but does not require weed control because there are few, if any, desirable forages present. In my experience, Kentucky horse pastures are maintained between these two extremes. Farm managers' primary concerns are plant identification in pastures and weed control.

Table 1: Common Kentucky Weeds

Warm-Season Weeds Cool-Season Weeds
Large crabgrass Muck thistle
Yellow foxtail Bull thistle
Goosegrass Canada thistle
Johnsongrass Buckhorn
Nimblewill Broadleaf plantain
Spiny amaranth Broadleaf dock
Buttercups Purple deadnettle
Common ragweed Chickweed
Asters Wild garlic
Perilla mint Star of Bethlehem
Hemp dogbane

Kentucky is located in the transition zone between warm-season and cool-season weeds, meaning weeds grow well in summer and winter. This provides horse pasture managers with the challenge of what pasture weeds, if any, they should control. Generally, poisonous weeds and weeds that inhibit grazing should be removed from a pasture. Poison hemlock grows widely across Kentucky and is toxic to horses and other animals. Although rarely eaten by horses, it should be removed from the pasture. Musk thistle and bull thistle are also found throughout Kentucky and inhibit grazing. Canada thistle occurs less frequently but also inhibits grazing and is more difficult to control. Large crabgrass and yellow foxtail are warm-season summer grasses. Horses graze the large crabgrass but not yellow foxtail. Buckhorn plantain is a cool-season plant that horses consume when pasture grass is limited. Other common weeds are listed in Table 1.

No one weed control solution exists for all these species. First, determine if there is a need for removing the weeds. A poisonous plant such as poison hemlock is controlled by hand weeding, mowing at the proper time, or by applying herbicides in late fall or early spring. Regardless of the method, do not allow animals to graze dying or decaying hemlock plants. Hand weeding and removal of the plants from the pasture is the safest method. Weeds such as thistles generally are too numerous to hand weed, and herbicides are needed.

For most weeds, mowing is not an effective control technique. Mowing might prevent some seed production; however, to kill many weeds, the mower must cut at about two inches or lower, which can reduce grass production. If mowing is not the best answer, consult your county extension agent for weed identification and proper herbicide use to achieve weed control. You might also review "Response of Pasture Weeds to Herbicides or Mowing" (Green and Witt, 2012), which is available from the local Kentucky County Extension Agent for Agriculture and Natural Resources. This publication contains photographs of commonly occurring pasture weeds and specific control tactics.

William Witt, a retired researcher in the Department of Plant and Soil Sciences University of Kentucky, provided this information. This was first printed in the Lloyd’s Equine Disease Quarterly, January 2013, Volume 22, Number 1.

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Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.