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Farm Management
First Posted Sept 27, 2008
Jul 26, 2010

Weeds in Horse Pastures

by Debora Johnson

Weeds Toxic to Horses

First of all, what is a weed? I would describe a weed as something growing that you do not want in your pasture. It may be harmful to your horse, aggressive to the desired forage in the pasture, unsightly, not of nutritional value to your horse, or just plain undesirable. One person's weed is another person's pleasure. We have all seen lovely buttercups growing in horse pastures, dandelions, Queen Annn's Lace, hoary alyssum, onions, etc. They may be pretty but are they desirable for your horse's health?

Weeds are in competition with your desired forage for soil moisture, sunlight, and nutrients. Horses selectively graze and will reduce some of the weeds just by the act of grazing. However, they cannot eradicate all weeds.

Steps to Get Rid of Weeds

  • Identify weed species
  • Rotational grazing (Let pastures recover)
  • Wet pastures-no horses
  • Extremely dry conditions-no horses
  • No Over grazing
  • Mow, but allow at least 4" showing above soil
  • Pull weeds by hand
  • Chemicals (Herbicides) when horses are on other pasture for at least 10 days
  • Reseed thin pastures or heavily weeded pastures
  • Keep horses off newly seeded pastures. Allow the root systems to establish themselves.
Weed's Lifespan

Weeds can be annuals, biennials, or perennials. Knowing the lifespan of a weed is helpful in the control process. Identification is really important.


"An annual germinates from seed, grows, matures, and dies in less than one year. Chemical control of annuals works best when applied in the spring to actively growing, young weeds. Mechanical control, such as mowing, is very effective against annuals.


Biennials require two years to complete their life cycles. They form a rosette (group of leaves at ground level) and store food in their roots the first year and flower the second year. Control measures, chemical or mechanical, are most effective when applied during the first year's growth. If treatment is delayed until the second year, early season application of a herbicide before bloom is important.


Perennials live more than two years, and grow back from the same roots year after year. Perennials move nutrients into their roots during fall to prepare for winter. Because of this, chemical control of perennials works best when applied in the fall to actively growing and well-developed foliage. As the nutrients move into the roots, the chemical will too. Application of herbicides in spring, or frequent moving during the summer is also effective in controlling growth until fall. However, mowing alone may take a several growing seasons to effectively control the perennial weeds.

Herbicides When using herbicides, always read and follow labels carefully. Always follow grazing recommendations after herbicide application. Herbicide may make toxic weeds more palatable to horses. Horses should be excluded from the sprayed area for seven to ten days after treatment if poisonous plants are present. Herbicides alone will not result in a weed-free pasture. Most herbicides control either grasses or broad leaves (i.e., alfalfa and clover). If you have a mixed pasture (both grasses and legumes like alfalfa and clovers), there are no herbicide options that will control unwanted weeds and leave BOTH legumes and grasses." Weed Control in Horse Pastures

For further information and reading the following links might be helpful:
Manure and Pasture Management for Recreational Horse Owners
Five steps to a great horse pasture
Farm Management Weeds

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