Perfect lawn, fact or fiction?

dandelion
Photo credit: Karen Zimmermann
Q:

Hi, We have a natural grass amphitheater that needs to be in top notch shape as we host weddings and events. The grass has dandelions and clover. What do you recommend? I am assuming we just need a broad leaf weed killer? I'm hoping we're not too late for a weed and feed or whatever you would recommend? It's very important that the grass doesn't get damaged in the process of removing the weeds!  

- Yamhill County, Oregon
A:


Yes, for a hope of a perfect lawn you need what is called a lawn weed killer. It will not kill your grass unless it is applied at too high a rate, but if the chemicals are formulated as esters and/or include triclopyr, you need to be careful spraying when the weather is too warm (above 75 degrees) as these formulations volatilize more easily and can damage newly budding shrubs and trees. Do not attempt to apply lawn weed herbicides with a back pack sprayer as they are extremely difficult to calibrate and almost always apply way over the label rate.

Since you have clover, you need more than the standard 3-way mix which includes 2,4-D, MCPP, & dicamba. There are a lot of choices of herbicides that will work (SpeedZone which includes carfentrazone for the clover and Q4 Plus which includes quinclorac are a couple of examples), but you will need to make 2 applications spaced 4 weeks apart if you want to kill all the weeds. One application will burn down the weeds but many will recover over time. In our trials, weed and feed has provided poor control of weeds (about 50% is all) vs. nearly 100% control using the correct herbicide and making 2 sprays.

Additionally, you want the lawn and the weeds to be healthy before you spray. If it is not, fertilize it and water it, if necessary. Do not apply before an expected rain event or irrigate for 24 hours after making the application. The herbicides are absorbed by the foliage and will be washed off by rain or irrigation.

I would hire a licensed contractor to make spray applications as there is a lot of things to consider, not the least is your safety as well as the safety of your customers. If you try to do it yourself, read the label very carefully and be sure to wear all the protective clothing recommended.

Brian McDonald
Turfgrass Research Assistant
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