when should i apply a preemregent to control the weed oxalis that is in my lawn? can you reccomend a particular product?



Preemergent herbicides will work only as the weed seed is germinating and emerging out of the soil. If you see oxalis already growing in your lawn, use a postemergent herbicide.

Oxalis is usually growing at the lawn edge or where soil is bare. Keep your lawn healthy and vigorous and it will out-compete oxalis.

Oxalis also seems to grow where lawns have become increasingly shaded by trees that are growing larger in the yard. Once the oxalis is eliminated, overseed that lawn area with a shade tolerant grass seed so that the oxalis won't re-infest that area.

The USU Extension publication "Landscape and Garden Weed Control" (http://extension.usu.edu/files/publications/HG508.pdf) recommends preemergent herbicides containing isoxaben or pendimethalin for good preemergent control of oxalis.

Postemergent herbicides containing the active ingredients 2,4-D, MCPP and dicamba will control oxalis after it is already growing. Herbicides containing triclopyr and clopyralid also provide good postemergent control.

Recommendations for shade-tolerant turfgrass cultivars is available in the USU Extension publication "Turfgrass Cultivars for Utah" (http://extension.usu.edu/files/publications/publication/HG_Grass_2004_01.pdf

Posted on 3 May 2007

Maggie Wolf
Horticulture Agent, Salt Lake County

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