Following the rough drought that we had, many pastures were full of weeds that persisted while cattle grazed on what little grass grew beside and under the weeds.
Looking at grown pastures that are full with goatweed (Wooly croton), Bitter sneezeweed, pigweed, ragweed, or horseweed, it is common for many stockmen to want to spray them to kill them. The problem is that all of those are summer annuals. As summer annuals, they are near the very end of their lifespan and have already made seed for the next year. To spray them now, would be a futile use of any herbicide and I typically recommend to mow the fully matured summer annual weeds down just to improve the look of the pasture. Any seed formed by these summer annuals will make their way onto to soil anyways.
But if your pastures are full of dogfennel, horse nettle, blackberry/dewberry vines, curly dock, pokeweed, and the tall yellow blooming goldenrod, these are perennials that we can fully expect to come back from the roots next spring.
Yet another classification of plants are biennials which have a two-year life cycle. Biennials such as wild carrot, thistles, and mullein start their growth in one season, then bloom and bear seed the following year. If you have fought thistles in the past, you know that they are currently in their “rosette” stage and will send up a main stalk with bloom come next spring.
Finally, every fall and early winter is the time for the ‘winter’ annual plants to begin their growth. The spring flush of growth in your pastures that may contain buttercup, prickly lettuce, wild mustard, wild geranium, henbit, or buttercup.
So, what is best for each of these weed issues? The answer differs for each one. Starting with summer annuals, a spring or early summer herbicide application is the obvious choice. Forage producers are often taught from research that a lower application rate of herbicide is very effective against seedling annuals. The same herbicide rate’s effectiveness decreases as the plant matures, reaching the point where the highest rate of an herbicide will have very little effect on a mature annual.
The perennial weeds provide more options. You can certainly treat perennials early in the growing season, but fall offers another great time to hit them as they are storing up reserves in their roots for the winter.
Fall is also a good time to treat biennials as they will continue through the winter to become a larger problem in the spring. I think of the thistles in my pasture now which are difficult to see as they lie low in their rosette state but will show themselves proudly in the spring.
Lastly, the winter annuals can be treated in the fall with a pre-emergent. A big conflict exists for stockmen who will be depending upon winter pastures of ryegrass, small grains, and clovers. These valuable winter forages also start from seed in the fall and early winter and a preemergent herbicide does not know the difference between desired seeds and weed seeds.
Reviewing the weeds I listed above, there are obviously many more that were left out. If you don’t know the names of your weeds and their growth habits, I encourage you to learn them. Study the enemy of your good pastures. Weeds take up vital space, water, and nutrients. A great weekly newsletter to learn about pasture management is ‘Forage Fax”. Look that up on your internet search engine and subscribe to the weekly email.
