Non-Atrazine Weed Killer for Floratam Lawn?

eaj2011January 11, 2012

Hi all. My noble efforts to go organic have left me with a dollar weed/crabgrass infested lawn. I am now reluctantly willing to do periodic weed sprays again, but want to avoid Atrazine because it has a high residual in the soil. Can someone please recommend a less toxic/low-residual weed killer for Floratam grass lawns??

My kids play on the grass, so I am hoping for the most worry-free synthetic product. (I already tried Ortho's Eco-Sense, which didn't really work. It only 'browned' about 10% of my weeds.)

I am in South Florida and want to spray now before the cold weather comes in late January.


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Good luck.

    Bookmark   January 11, 2012 at 4:01PM
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dchall_san_antonio(8 San Antonio)

TW is referring to a couple of things. The weed killers without atrazine kill St Augustine, so you'd be screwed. The other thing is that weed killers with atrazine have been taken off the market, so you're screwed either way. If you find one with atrazine, don't spray the soil. Just spray the leaves of the weeds.

Many plants have the name dollar weed. Can you post pictures of yours so we can tell you what you really have? Some dollar weeds will die if you look at them wrong and others will eventually take over the land masses.

Now is not the time to kill weeds. Wait until spring when they are popping. For best results fertilize first, wait 2 weeks, then spot spray.

What happened with your organic program? Whether you use organic fertilizer or synthetic should make no difference in weeds. The problem with weeds is almost always a watering problem (too frequent) or, secondarily, a mowing problem (too low).

    Bookmark   January 11, 2012 at 11:31PM
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My over-watering issue came when our drought in South Florida ended this year and we got slammed with long periods of rain. My weed problem was barely noticeable before that, but as you can see from my photos, it's a big problem now.

I used to have a lawn company spray my lawn with weed killer every two months, but I stopped doing that once my 3-year-old twins started playing in the grass more often, rolling around like chimps, often as naked as chimps too. But I went many months without weeds even after stopping the spraying service.

I tried Eco-Sense from Ortho, but it didn't work. I am considering trying Corn Gluten in the Spring, but I don't have much hope for it based on the what I've read. Thus, I am now willing to spray again, but I want to be able to kill the existed weeds yet know that after a few days and one watering-in, my kids can play on it again.

So any suggestions or plans of action are (desperately) welcome.

When you say now is not the time to kill weeds, does that mean the cold weather will eventually kill all my existing weeds, so there is no need to spray kill them?

Also, what is the stringy week I am holding? It is popping up all over too.

I've never added photos before, so forgive me if I duplicate any...

First two are suspected Dollarweed.
Third is suspected crabgrass.
Fourth is stringy weed.


    Bookmark   January 12, 2012 at 12:38PM
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#2 is Dollarweed A/K/A Pennywort
#3 looks like Crabgrass
#4 is some type of Sedge

Penoxsulam is a fairly new broad spectrum, broad leaf weed killer approved for St Augustine lawns. Lesco has a weed & feed with this in it avaliable in Florida. It should be effective on the Dollarweed but I don't know about the Crabgrass or Sedge.

I have not used this product but have purchased some for next Spring upon the advice of a friend. He lives in Orlando and reports good results.

Hopefully someone who has used this will chime in.


Here is a link that might be useful: Penoxsulam

    Bookmark   January 14, 2012 at 12:50PM
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dchall_san_antonio(8 San Antonio)

The dollar weed is the one you have worry about first. There are three kinds of plants that grow in lawns. One is classified as grass or your target turf grass (these include common lawn grasses like turf type fescue, Kentucky bluegrass, St Augustine, hybrid bermuda, centipede, zoysia). Another is broadleaf weeds (clover, dichondra, pennywort, spurge, horse herb, black medic, creeping charlie, and others). The third category is grassy weeds which do not tame well (sedges (nutgrass and ), Johnson grass, crabgrass, common bermuda, barnyard grass, annual bluegrass, goose grass, and others). The broadleaf class of weeds are the bane of St Augustine lawns because they will easily shade out new growth. The St Aug will thin out fast and disappear in just a few months. With grassy weeds, the coarse blades of the St Aug usually shade them out.

Fortunately there are different kinds of chemicals which kill the different kinds of plants. Broadleaf weeds are killed by the 2-4,d chemicals in Weed-B-Gone. Unfortunately St Aug is sensitive to 2-4,d also. Most plants are killed with atrazine but St Aug is not. I have not heard of penoxsulam, but then I don't pay much attention to herbicides. There is also Grass-B-Gone and Sedgehammer for the other weeds. Again, unfortunately, lawn grasses are killed by the Grass-B-gone product. The one good herbicide specialist is Sedgehammer.

You might try the penoxsulam in a small spot as a test. Otherwise look for something with atrazine. Occasionally you see it as I described above.

Your middle picture looks like crabgrass compared to St Aug, but it is the wrong time of year for crabgrass. I'm going with centipede. It looks like St Aug in many ways but it has pointy blades where St Aug has a boat-tailed shaped blade at the end. Simply taking care of the lawn with water and fertilizer will kill the centipede. Here is a picture of the two grasses.

Then the prescription is to get a broadleaf weed killer that is safe for St Aug. My comment about this not being the time of year to kill weeds has to do with the plants not being in a fast growth state. You can try it. It could be your area is warm enough that everything is growing. I would fertilize with organic fertilizer, wait 3 full weeks, and then spray. You want the weeds to be growing and healthy before spraying. In the mean time raise your mower all the way up and weld it in place. There is never any reason to mow St Aug lower than full height. And keep the water off as much as you can.

    Bookmark   January 15, 2012 at 12:22AM
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Thank you both for the replies. This helps me immensely.

    Bookmark   January 15, 2012 at 9:03AM
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