Karen Cambre, Sharpe, Kenneth W.
News article for June 18, 2018
We went through a dry period, but our typical summer shower pattern has returned. That is good for livestock pastures and lawn grasses.
When grasses stop growing it is usually easier to see weeds growing since they seem to survive even in harsh growing conditions. One of the complaints I have heard and seen is the low mounding dark green plant with small leaves growing in lawns. It has 3 small leaflets, like clover, with a pink to purple flower. The stem gets woody as it matures and the plant takes over lawn grasses.
This broadleaf weed is known as annual lespedeza or common lespedeza. It is an annual plant so it dies in the winter and reproduces by seed. It is just now starting to flower and this is when seeds are produced. Now would be a good time to control annual lespedeza before it produces more seed for next year’s weeds.
It is too hot now for the 2,4-D blends that we used back in the spring. The best choice is to use a herbicide with metsulfuron methyl. I see it sold as MSM-60. This herbicide is not temperature sensitive, so it will not burn lawn grasses. It is however a little slow to act so do not panic when you check the results in a week or two. My own observations have been that it takes 30 days to show any results and much better at 60 days, but you will be very pleased. It has only taken me one spray with metsulfuron methyl to control annual lespedeza. I will note that MSM will kill Bahia grass also so if you have and want Bahia grass, beware.
Another summer time weed that is thriving now is Virginia Button Weed (VBW). This is also a broadleaf weed, but it is a persistent perennial. Virginia Button Weed has a 4 petal small white flower that is prominent. It is a prolific seed producer and each seed has 2 antennae, or horns, emerging from them. The foliage is succulent and grows in clumps right over the top of lawn grasses. It is very invasive and very difficult to control.
The best approach to controlling VBS is to try to knock back the perennial mother plants as soon as they break dormancy next spring. You can use a 2,4-D blend in your general broadleaf control program in late April or early May. Then you will get seeds germinating by June so you want to follow up, or for this year, start now and use the same product that I recommended for annual lespedeza, which is MSM. If you are treating the entire lawn with MSM, you get the benefit of controlling common lespedeza and getting some relief from VBW.
Remember that control is slow and not nearly as good on VBW as annual lespedeza, but it will move you in the right direction. Come back in for a July treatment in 30 days and spot treat all VBW plants that you see. Make your last treatment in August in 30 more days and you will see a reduction of VBW, but it will not completely eliminate the problem. You will still have seed available for more plants next year.
In some cases I have pulled up the large massive plants to allow the grass to recover, but be sure to throw the VBW plant with all of its seeds in the garbage can. Almost every seed will germinate, so do not just drop the plant on the ground.
When you treat your entire lawn with MSM your grass will slow its growth dramatically. A side benefit to making a treatment just before leaving for vacation is that your lawn will not grow as tall and will look neater upon your return.