A well balanced mix of forbs and grasses will give your horses the best nutritional benefit of grazing. Weeds can be a thorn in the side of any agronomist but can be dealt with with fair ease.
Tackling all of the weed problems in any size pasture is a formidable task. From a botanical perspective it is easier to break the whole group of pests into three categories: annuals, biennials, and perennial.
An annual plant is one that dies every fall and drops seeds for self propagation. A biennial has a two year life cycle. Sometimes biennials can look very different between the two years which it lives. Typically the first year is to establish roots and a small photosynthesizing unit above ground and the second year pushes up a flowering portion before dropping seeds.
Perennial plants live for years and often become woody.
To battle any or all of these plants takes consideration. Which is the largest nuisance? Can we take out the undesirables without harming the graze plants? Am I to blame for their success? This last question may not seem fair but a farmer who overgrazes an area of pasture is just as to blame as the horses.
Knowing the carrying capacity of your area and not overdoing it will considerably help your pasture. Weeds are weeds because they grow where we don’t want them. Often they are very successful because they are hearty plants.
If they are undesirable for your horse to nibble then they will have the advantage of not being damaged and therefore having healthier roots which leads to general and reproductive health. With all of the benefits of not being grazed, they will set seeds and succeed. A well managed pasture allows your crop to compete with weeds.
With a successfully started crop one can then battle the undesirables. I avoid herbicides when I can and so I will only mention those methods of weed control that I support wholly.
My plan during the growing season is to keep the desirable plants as healthy as possible. Sometimes this means removing my horses from the pasture during high stress times like low rain or very hot conditions.
I practice a mowing technique that takes the grazed down portion where my crop of desirable are nibbled down and the weeds are strong and I mow. This sets back the weeds and gives my plants time to compete. With luck and a little thought you can stay on top of your pasture weeds.