Pasture and hay production in Tennessee follows a relatively predictable pattern. Forages begin to grow in March, do well until mid-June, slump some until September, grow in fall until November, then slump until the next March. This cycle is one that many of you have seen completed dozens of times. Another component of this cycle occurs during the summer season. It is the emergence of warm-season weeds.
After the spring growth of tall fescue is either cut or grazed, weed seeds will germinate and an entire crop of summer weeds begin to develop. Horsenettle, ragweed, spiny pigweed, and tall ironweed are just a few examples. If left unchecked these weeds can quickly begin to dominate a pasture. In my opinion, there are few things that make a pasture looks worse than a heavy population of summer weeds. Part of the problem is that these weeds can take over because the tall fescue is slumping, offering very little competition to keep these weeds from dwarfing everything else in the field.
One of the control methods many producers have used is clipping. Trying to stay ahead of the weeds by timely mowing has been used for a long time. This method can reduce the amount of weed in the field, as well as reduce the seed production from these weeds. The problem is that being just a little late on the mowing can dramatically reduce the benefit. At minimum the weeds can dominate the field. But you could also be late enough that the plants have been allowed to produce seed for next year’s weed crop.
Fortunately, there are herbicides that are available to control many of these weeds. Whether it be Grazon Next for horsenettle or 2,4-D for spiny pigweed