Preen is a germanation preveter. It prevents seeds in the soil from germinating successfully and ordinarily is goosd for a season. Is it safe? Probably, but the label info should be the final arbiter along with any direct anecdotal experience some may have had with it. Be aware that where ever you use it, you will be unable to do direct seeding of any crops or ornamentals. Though for the most part you will be able to transplant successsfully into treated areas. When you do this, you will break up the "weed Barrier" the preen creates on the soil surface and it is likely you will see weeds develop in the disturbed soil areas.
As mentioned, don't over use and be aware there may be a few established plants that may be susceptable. Use cautiously.
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