Weed Management Plans for Horse Pastures
Fall is a good time to evaluate the quality of your horse pastures each year, because it is easy to see which weeds were most prevalent and uncontrolled during the summer and are now large and seed-producing. It is also a good time to develop a weed management plan for pastures in the coming year. When creating an effective weed management plan, consider: the pasture’s purpose, weed species and abundance, which weeds should be controlled and the method of weed control, and sources of information.

Purpose of the pasture.

If pasture is a significant portion of your horses’ diet, you’ll want a high-quality, nearly weed-free forage. Conversely, a “pasture” maintained as a drylot for feeding horses will contain many weeds, but there is little reason to control these weeds since there are few, if any, desirable forages in the drylot. Kentucky horse pastures usually are maintained between these two extremes. Property owners often ask why these weeds are in their pastures, followed by what they should do about them. Forages grown with adequate fertility and not overgrazed will limit weed occurrence but not prevent all weeds from growing.

Weed species, abundance, and distribution.

Plants that we call weeds grow in ecological niches–environments that allow for germination, vegetative growth, and maturation. Horse pastures provide several of these ecological niches that allow some weeds to thrive. Kentucky is located in the temperate transition zone that in which both warm-season and cool-season plants grow.

Warm-season weeds germinate in spring or early summer, grow, and produce seeds before frost.  Cool-season weeds germinate and produce some growth in the fall and seeds the following spring or summer.

When pastures house many weed species, horse pasture managers face the challenge of determining which weeds, if any, they should control. The most abundant weeds in horse pastures are usually annual species that produce thousands of seeds. Spiny pigweed, also known as spiny amaranth, produces more than 100,000 seeds per plant. This weed is widespread and occurs most often in compacted areas along fences and around feeding and watering areas of pastures. Spiny pigweed is also a good example of the “patchiness” of weeds; they often grow only in certain portions of the pasture where their ecological niche occurs.

Which weeds to control and method and time of weed control.

Generally, you should remove poisonous weeds and weeds that inhibit grazing from a pasture.

Poison hemlock occurs widely across Kentucky and is toxic to horses and other animals. Although horses rarely eat it, you should remove it from the pasture.

Musk thistle and bull thistle are 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 grasses of summer. Horses graze the large crabgrass but not yellow foxtail.

Buckhorn plantain is a cool-season plant that horses consume when pasture grass is limited.  Many small, tender “weeds” are nutritious and readily consumed when small but rarely consumed as large plants.

Methods of removing horse pasture weeds are limited to hand removal, mowing, and herbicides, and each has its advantages and disadvantages.

Hand-weeding can be very effective and is particularly useful for removing poisonous plants, such as poison hemlock, from a pasture. You should not only control poisonous plants but all remove them from the pasture to prevent animals from consuming them.

The downside of hand-weeding is that the process is slow and inefficient for large areas.  Mowing is rarely effective at killing weeds in pastures—mowing low enough to kill the weeds (2 inches or less) removes valuable forage. Mowing heights of about 6 inches will keep some large weeds from producing seeds but does not control smaller weeds.

Herbicides are efficient and provide excellent control, but in transition zone areas such as Kentucky, one herbicide will not control all the weeds with one treatment.

There are optimum times to control weeds with herbicides. The following months are the preferred time for herbicide treatment for several weedy species in Kentucky:

  • October-November: Common chickweed, henbit, purple deadnettle, dandelion, buckhorn plantain, musk thistle, bull thistle, Canada thistle, poison hemlock
  • February-March: Buttercups, curly dock, broadleaf dock, chicory
  • May-July: Spiny pigweed, white clover, hemp dogbane, goldenrod, cocklebur, perilla mint, common ragweed, jimsonweed

Sources of information.

Consult your local Cooperative Extension Service agricultural agent for specific information on herbicides in your area. Remember, not all herbicides are registered for use in all states and countries, so read the label carefully, and follow all directions. Many Cooperative Extension Services have publications regarding weed control in pastures, including:

William W. Witt, PhD, emeritus professor and weed scientist with the University of Kentucky’s Department of Plant and Soil Sciences, provided this information. Email: wwitt@uky.edu

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