Round Up degrades quickly but is not a pre-emergent.

There are organic varieties that use corn gluten that should be pretty safe. I use Bayer Durazone. Kills exisiting weeds and prevents new ones for 6 months. It bonds to the soil to provide a barrier to stop weeds.

My local stores don't seem to carry much in the way of pre-emergents. Especially the organic ones. About the only one I've seen is Preen and for some reason I think this stuff would prevent all new growth and not just weed seeds. Though admittedly I've never even read the label on the stuff...

The only stuff my local stores seem to carry are the chemical weed killers that are fairly turf specific. These are out for me as my 'turf' is some mix-matched blend of different grass types, so using a turf-specific weed killer would leave me with brown patches and areas. Maybe some day I'll splurge and get some St. Augustine to lay down over my lawn areas and homogenize my lawn, but for now, I have other things I would rather spend my money on.

But I would love to hear other people's experiences with these pre-emergents, especially the organic ones. If they work, they might be worth ordering a bag online. Especially if they stop Southern Sandspur. I'm just worried about also ending up putting a halt to Mimosa seed germination and other types while trying to halt the weeds.

Leekle, it will put a stop to all seed germination indiscriminately as far as I understand, mimosa too.

I'm hoping someone will chime in regarding potential long term impacts on watershed, like you said, overall growth of existing plants (in theory it should not impact plants, only inhibit germination of seeds, but I wonder...), does it lead to soil toxicity in the long term. Really I'm interested in any first hand experiences or even opinions.

I recently moved to Florida from NY. In NY we had well and septic and I gardened organically. Years earlier I used Preen on a few large flower beds. It did work if you put it down early spring. It does nothing after weeds germinate. It worked but I stopped using it for obvious reasons. I had no idea what it would do to the soil and water.

I grew many large beds, both flower and vegetable without any chemicals. I composed heavily and did weed by hand and hoe.

Florida seems to be a different story. Weeds appear before your eyes. I'm having the same issues as you have. I do think as I continue to add thick layers of compost, I will get a handle on the weed growth.

My daughter lives in Connecticut and also gardens organically. She has been using corn gluten on her lawn for about 4 years. It is slow going and takes a few years to start making a difference. It is also expensive if you have a lot of lawn. Her property is beautiful as is her lawn, which is a mix of grasses and green weeds!

Jane

Preen has an organic variety for vegetable gardens but obviously you could also use it in flower beds. It is corn gluten. The problem with weeds in Florida is that many weed seeds blow in so you will always be fighting new one. If you use a lawn service they can carry all sorts of weeds and disease on their equipment.