I know many people sing the praises of horse herb, and our local garden nurseries even sell it. But, it is driving me crazy taking over flower beds and even my well established lawn! I immediately get rid of flowers that it develops but I think it spreads underground...and therein is the problem.

Does anyone know how to get rid of it in a St. Augustine lawn without killing the lawn?

It's to bad that it is so invasive, otherwise I'd leave it in flowerbeds because it does attract pollinators.

What a neat looking plant!
Looks similar to melampodium...

Send me some...

Look for a product with Atrazine. It works as both a pre-emergent and selective post-emergent control. For an organic solution, you're stuck with fingers or a lot of vinegar.

@CalPolygardener
Thank you for the suggestion. I just ordered some Atrazine. I'll report back about how it works!

@CalPolygardener The Alatrazine arrive yesterday. The label does not mention horse herb as one of the controlled weeds. Have you used this on horse herb before?

Any broadleaf herbicide should work. I think 2,4-D would be safer. Follow the directions on the label and your lawn should be unharmed. Horse herb (also called prostrate ground flower) is often suggested as a grass substitute where saving water is important. It also grows in areas too shady for most grass. BUT it is quite aggressive.

Thank you @porkpal! I am trying to get rid of the horse herb that is moving into my St. Augustine lawn. I've used Natria herbicide on areas that I am not concerned about protecting (no lawn, no flower or shrub areas). As mentioned, I've had a bit of success with Weed B Gone, but the horse herb spreads underground, so I really need to get it under control.

Lot's of people do love it as a lawn substitute, and if it was not so invasive, I would leave it in a couple of areas that don't have lawn. Thanks again!

What brand of Atrazine do you have? I haven't used it myself, but it's the answer I get when looking for a control. The label may say something like "broadleaf weeds in St Augustine grass" without listing it specifically. The other reason its recommended for is weed prevention in St Augustine.

I've heard it can kill your shrubs too... I've never used it.

I bought the actual brand name Altrazine manufactured by Southern Ag. Yes, it will kill shrubs and flowers too.
I would only use it on the lawn, and try to control the flower beds some other way. I just called the manufacturer and they do not know if it will kill horse herb or not. My primary concern is keeping it from taking over my St. Augustine lawn, which is otherwise very thick and lush. Horse herb spreads underground so it makes it difficult to fight.

Very frustrating! When I moved in, I was bombarded with Thistle. Eliminated that, even though my next door neighbor still lets it grow everywhere. The following year Oxalis invaded. Got rid of that too! Last year when I saw the first horse herb plants emerging, I thought it was Oxalis returning. But it wasn't and the horse herb is worse and exacerbated by so many people growing it as ground cover.

It has the "many other broadleaf weeds" statement to cover their butts. It is the recommended product for control from multiple sources.

It's finally getting cool enough to use the Altrazine. I'll update when I have results to share!