By Dr. J.D. Green, Extension Weed Scientist - Using good pasture management practices can help minimize weeds and unwanted plants in grass pastures and hayfields. To get the most quantity and quality from pastures, use management practices that encourage growth of a vigorous, dense stand of forage grasses and limit germination and growth of unwanted plants. Weeds that reproduce by seed readily germinate in thin pasture stands, and unwanted plants are more prone to become established in these areas.

Good management starts with timely mowing and good grazing practices. Mowing before weedy plants can produce seeds helps prevent production and spread of weeds. Where perennial weeds dominate, frequent mowing can curtail growth by depleting their root reserves. If you use continuous grazing, be sure to avoid over-grazing that reduces the competitive capabilities of desirable forage species.

Maintaining the optimum soil acidity/alkalinity and fertility levels is another weed prevention practice. Soil test on a regular basis to ensure that proper nutrients are available for pasture growth and quality. Also, keep fence rows and adjacent fields free of troublesome weeds such as musk thistle, poison hemlock, and multiflora rose.

In some cases, herbicide use may be the most effective weed-control method. However, it’s important to remember that you may not be able to effectively control all weeds with a single herbicide product applied only one time. When considering herbicide use, determine the types of weeds to be controlled, their life cycles and the best time of year to apply the herbicide.

If possible, avoid applying herbicides in mid-summer, because many common products for pastures can injure nearby, sensitive broadleaf crops like tobacco, grapes, vegetables and ornamentals, especially under high air temperatures and humidity. Generally, the best times to apply herbicides to grass pastures is in late summer to early winter months or in the late winter and spring after plants begin actively growing, depending on the growth stage of target weeds. Remember to note any precautions and abide by any grazing or forage harvest restrictions.

As is true with any good weed management program, use a variety of practices to prevent and combat weed infestations in pastures. Timely mowing can be an effective mechanical weed control practice and grazing management can be a good cultural practice. Whereas, apply herbicides when the situation warrants their use.